Electron Yield Measurements of High-Yield, Low-Conductivity Dielectric Materials

Materials exposed to the space plasma environment acquire electric charge, which can have harmful effects if it leads to arcing or electrostatic breakdown of important spacecraft components. In fact, spacecraft charging is the leading environmentally induced cause of spacecraft anomalies. This study focuses on measuring electron yield, a property of materials that describes how many electrons are ejected from a material under energetic electron bombardment, which can vary depending on the energy of incident electrons. Intrinsic electron yield is defined as the average number of electrons emitted per incident electron from an electrically neutral material. The specific aim of this work is to improve yield measurements for insulator materials, which can be difficult to test using conventional methods due to charge accumulation in insulators.Most studies of electron yield use a steady current electron beam in a vacuum chamber to irradiate materials to be tested. By comparing the amount of current deposited in the material to the total incident current, the emitted current can be calculated. This works well for conductors; however, insulators charge up quickly, which either repel incident electrons or reattract emitted electrons producing erroneous yield measurements. This study improves on methods that use a pulsed electron beam to measure yield with small amounts of charge per pulse, as well as neutralization methods to dissipate stored charge between pulse measurements.The improvements to instrumentation and data analysis techniques are quantified to demonstrate their validity. These improvements will allow for continued studies on extreme insulator materials. Future studies will provide new understanding of interactions between electron radiation and materials, which will allow for better modeling of spacecraft charging and the development of materials that meet desired electron emission specifications

An Investigation of First-Year Teacher Induction Programs in Jesuit Secondary Schools within the California Province

This mixed methods study invited principals (n=5) and first-year teachers (n=25) in five Jesuit secondary schools in the California Province to participate. Online surveys and follow-up online interviews were designed to assess the degree to which the schools met 11 standards that constituted the conceptual framework for the study: (a)Program vision, goals, and institutional commitment, (b)Formation of the Ignatian educator, (c)Program administration and communication, (d)Principal engagement, (e)Program assessment, evaluation, and accountability, (f)Assessing first-year teacher practice, (g)First-year teacher professional development and learning communities, (h)Mentor role and responsibilities, selection, assignment, and assessment, (i)Mentor professional development and learning communities, (j)Focus on instructional practice, and (k)Focus on equity and universal access. Ten of the 11 standards were adapted with permission from the New Teacher Center\u27s (2011)Induction Program Standards. The second standard regarding Ignatian formation was adapted from the Jesuit Secondary Education Association\u27s (2011)Profile of an Ignatian Educator. Overall, the study revealed that all five schools developed and implemented some form of an induction program for their first-year teachers during the 2012-2013 academic year. The perception data indicated that all five schools demonstrated a strong commitment to (b)Formation of the Ignatian educator. In contrast, the respondents reported the most need for growth in (e)Program assessment, evaluation, and accountability. The respondents showed modest support for the remaining nine standards, indicating the potential for improvement. For example, first-year teachers reported the need for the presence of mentor teachers who play a supportive role throughout the academic year. The results of this study invite administrators in Jesuit secondary schools to develop and implement robust first-year teacher induction programs

Spectroscopy of a synthetic trapped ion qubit

$^{133}\text{Ba}^+$ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1/2 nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser-cool the synthetic $A$ = 133 radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the $6^2 \text{P}_{1/2}$ $\leftrightarrow$ $6^2 \text{S}_{1/2}$ and $6^2 \text{P}_{1/2}$ $\leftrightarrow$ $5^2 \text{D}_{3/2}$ electronic transitions that are needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. We also report the $6^2 \text{P}_{1/2}$ $\leftrightarrow$ $5^2 \text{D}_{3/2}$ electronic transition isotope shift for the rare $A$ = 130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes

Validation of Enhanced Electron Yield Measurements of Low-Conductivity, High-Yield Materials

Materials exposed to electron bombardment can charge positively or negatively, depending on the number of electrons ejected from the material. This electron emission is the main mechanism which drives spacecraft charging, which can induce electrostatic breakdown of insulators and damage pertinent electrical, optical, and mechanical components. The electron yield (ratio of emitted to incident electrons) is an intrinsic property which characterizes how a material will charge under these types of conditions. However electron yield of insulators is very difficult to measure because measurement causes charge buildup. To measure the intrinsic yield (yield of uncharged material) of insulators new methods have been developed which minimize incident charge using a pulsed beam, analyze the emitted electron energy distribution using an improved hemispherical grid retarding field analyzer, and neutralize acquired charge using UV and low-energy electron flooding. Modifications were made to the instrumentation to increase electron measurement efficiency, and improve charge neutralization techniques. New analysis methods produced an increased signal-to-noise ratio and allowed for measurement of yield for charges as small as 30 electrons (~ 5 attocoulombs). Various tests were performed to validate the changes made and quantify the improvement. These new methods give high-accuracy absolute yield measurements because they allow for the measurement of all incident and emitted charges. The improved charge neutralization methods allow for yield measurement with negative and positive charging. Results of validation tests and measurements of extreme insulator yield are presented. * Supported by a Utah NASA Space Grant Consortium Graduate Fellowship

Drosophila Ctf4 is essential for efficient DNA replication and normal cell cycle progression

Background Proper coordination of the functions at the DNA replication fork is vital to the normal functioning of a cell. Specifically the precise coordination of helicase and polymerase activity is crucial for efficient passage though S phase. The Ctf4 protein has been shown to be a central member of the replication fork and links the replicative MCM helicase and DNA polymerase α primase. In addition, it has been implicated as a member of a complex that promotes replication fork stability, the Fork Protection Complex (FPC), and as being important for sister chromatid cohesion. As such, understanding the role of Ctf4 within the context of a multicellular organism will be integral to our understanding of its potential role in developmental and disease processes. Results We find that Drosophila Ctf4 is a conserved protein that interacts with members of the GINS complex, Mcm2, and Polymerase α primase. Using in vivo RNAi knockdown of CTF4 in Drosophila we show that Ctf4 is required for viability, S phase progression, sister chromatid cohesion, endoreplication, and coping with replication stress. Conclusions Ctf4 remains a central player in DNA replication. Our findings are consistent with what has been previously reported for CTF4 function in yeast, Xenopus extracts, and human tissue culture. We show that Ctf4 function is conserved and that Drosophila can be effectively used as a model to further probe the precise function of Ctf4 as a member of the replication fork and possible roles in development

Statistical Variation of Diverse Light Emission Measurements from Bisphenol/Amine Epoxy Under Energetic Electron Bombardment

Dielectric materials subjected to energetic electron fluxes can emit light in several forms. We have observed three distinct types of emissions: (i) short-duration (\u3c1 ms), high-intensity electrostatic discharge (ESD) or “arc” events; (ii) intermediate-duration, high-intensity events which begin with a bright arc followed by an exponential decay of intensity (~10 to 100 s decay constant), termed “flares”; and (iii) long-duration, low-intensity emission, or cathodoluminescence, that continues as long as the electron flux is on. These events were studied for bulk samples of bisphenol/amine epoxy, using an electron gun with varying current densities (0.3 to 5 nA/cm2) and energies (12 to 40 keV) in a high vacuum chamber. Light emitted from the samples was measured with a high-sensitivity visible to near-infrared video camera. Results of the spatial and temporal extent for each type of event are presented as well as a discussion of how absolute spectral radiance and rates for each type of event are dependent on incident electron current density, energy, and power density and on material type, temperature, and thickness. Applications of this research to spacecraft charging and light emissions are discussed

Protocol for a randomised controlled trial investigating the effectiveness of an online e health application for the prevention of Generalised Anxiety Disorder

BACKGROUND Generalised Anxiety Disorder (GAD) is a highly prevalent psychiatric disorder. Effective prevention in young adulthood has the potential to reduce the prevalence of the disorder, to reduce disability and lower the costs of the disorder to the community. The present trial (the WebGAD trial) aims to evaluate the effectiveness of an evidence-based online prevention website for GAD. METHODS/DESIGN The principal clinical question under investigation is the effectiveness of an online GAD intervention (E-couch) using a community-based sample. We examine whether the effect of the intervention can be maximised by either human support, in the form of telephone calls, or by automated support through emails. The primary outcome will be a reduction in symptoms on the GAD-7 in the active arms relative to the non active intervention arms. DISCUSSION The WebGAD trial will be the first to evaluate the use of an internet-based cognitive behavioural therapy (CBT) program contrasted with a credible control condition for the prevention of GAD and the first formal RCT evaluation of a web-based program for GAD using community recruitment. In general, internet-based CBT programs have been shown to be effective for the treatment of other anxiety disorders such as Post Traumatic Stress Disorder, Social Phobia, Panic Disorder and stress in clinical trials; however there is no evidence for the use of internet CBT in the prevention of GAD. Given the severe shortage of therapists identified in Australia and overseas, and the low rates of treatment seeking in those with a mental illness, the successful implementation of this protocol has important practical outcomes. If found to be effective, WebGAD will provide those experiencing GAD with an easily accessible, free, evidence-based prevention tool which can be promoted and disseminated immediately

UAV for Medical Equipment Distribution

This Final Design Review report documents the senior project participating in the Vertical Flight Society’s 38th Annual Student Design Competition sponsored by The Boeing Company. The goal of this project and competition is to develop an unmanned vertical lift for medical equipment distribution capable of safely delivering a 50 kg payload over distances up to 200 km. This system must be autonomous and have a backup plan to land if any part of the system malfunctions. We discuss the research and justification that drove the selection of the aircraft configuration, a winged quadcopter with a rear propeller. Furthermore, we document our reasoning and analysis for sizing and shaping of the rotors, propeller, and wings, selecting a hybrid-electric turbogenerator for the powerplant, designing the payload release mechanism, and sizing and shaping of the semi-monocoque structure. We provide analysis that numerically verifies our UAV’s ability to meet the requirements for payload capacity, range, mission time, and geometric envelope