Electrical Activation Studies of Silicon Implanted Aluminum Gallium Nitride with High Aluminum Mole Fraction

This research demonstrates a method for producing highly conductive Si-implanted n-type aluminum gallium nitride (AlxGa1-xN) alloys, and represents a comprehensive analysis of the resulting material\u27s electrical and optical properties as a function of Al mole fraction, anneal temperature, anneal time, and implantation dose. Highly conductive alloys are critical to the fabrication of devices operating in deep UV, high-temperature, high-power, and high-frequency environments, and thus this research is significant in regard to the application of such devices. The AlxGa1-xN wafers of this study, with Al concentrations of 10 to 50%, were implanted at room temperature with silicon ions at energies of 200 keV with doses of 1x1014, 5x1014, and 1x1015 cm-2 and annealed from 1100 to 1350 C for 20 to 40 minutes in flowing nitrogen. Excellent activation was achieved for each of the implanted silicon doses for all of the five Al mole fractions studied, with most activation efficiencies above 90%. These activation efficiencies are the highest reported activations, to the best of my knowledge. The mobilities were found to decrease as the Al concentration of the AlxGa1-xN was increased from 10 to 50% and also as the implanted silicon dose was increased. Typical mobilities ranged from 101 cm2/V s for the Al0.1Ga0.9N implanted with 1x1014 cm-2 silicon ions to 35 cm2/V s obtained for the Al0.5Ga0.5N implanted with 1x1015 cm-2 silicon ions. The cathodoluminescence results support the electrical results in determining the optimal annealing conditions

Environmental Risks and Benefits of Nano-Enabled Clean Energy Technologies

Engineered nanomaterials (ENMs) are increasingly incorporated into clean energy technologies due to observed improvement in technological and system performance. Though these materials could revolutionize many products and technologies, increased use of ENMs can also introduce uncertainty and risks that are difficult to predict. Increase in ENM use could significantly increase ENM releases to the environment across their life cycle, from material synthesis to end-of-life. To address knowledge gaps and uncertainties, this work assesses a portfolio of ENMs from a systems perspective. First, characterization and quantification methods were developed for three carbonaceous ENMs, fullerenes (C60, C70, and derivative PCBM), which have promising application in solar technologies. Empirical ecotoxicity assays and predation studies were performed to determine ecotoxicity and predation effects. Next, an integrated model predicted potential risks of ENM accumulation by estimating potential manufacturing locations, spatial concentrations, and potential ecological risks. This was followed by an adaption of portfolio optimization, a model traditionally used to optimize investment performance, to model potential environmental and economic risks and simultaneous performance benefits and inform safe nano-enabled design. Ecotoxicity findings demonstrate differences among fullerenes where organisms exposed to fullerenes also experienced significantly increased predation risk, underscoring the need to consider potential system-level effects. Based on manufacturing locations, potential ENM exposure may be within buffer distances of sensitive ecosystems. However, modeled ENM accumulation would only reach levels associated with ecotoxicity risk under extreme scenarios. Future ENM use-patterns can be informed by the portfolio optimization approach, where optimal portfolios are determined by the materials-mix that yielded the greatest overall performance return while minimizing the portfolio risks. These novel methods and tools contribute to the knowledge of the benefits and risks of ENMs, which will help to guide more responsible and proactive policy and planning around ENM development and use

Electrostatically Tunable Meta-Atoms Integrated With In Situ Fabricated MEMS Cantilever Beam Arrays

Two concentric split ring resonators (SRRs) or meta-atoms designed to have a resonant frequency of 14 GHz are integrated with microelectromechanical systems cantilever arrays to enable electrostatic tuning of the resonant frequency. The entire structure was fabricated monolithically to improve scalability and minimize losses from externally wire-bonded components. A cantilever array was fabricated in the gap of both the inner and outer SRRs and consisted of five evenly spaced beams with lengths ranging from 300 to 400 μm. The cantilevers pulled in between 15 and 24 V depending on the beam geometry. Each pulled-in beam increased the SRR gap capacitance resulting in an overall 1-GHz shift of the measured meta-atom resonant frequency

Psychosocial Characteristics and Obstetric Health of Women Attending a Specialist Substance Use Antenatal Clinic in a Large Metropolitan Hospital

Objective. This paper reports the findings comparing the obstetrical health, antenatal care, and psychosocial characteristics of pregnant women with a known history of substance dependence (n = 41) and a comparison group of pregnant women attending a general antenatal clinic (n = 47). Method. Face-to-face interviews were used to assess obstetrical health, antenatal care, physical and mental functioning, substance use, and exposure to violence. Results. The substance-dependent group had more difficulty accessing antenatal care and reported more obstetrical health complications during pregnancy. Women in the substance-dependent group were more likely to report not wanting to become pregnant and were less likely to report using birth control at the time of conception. Conclusions. The profile of pregnant women (in specialised antenatal care for substance dependence) is one of severe disadvantage and poor health. The challenge is to develop and resource innovative and effective multisectoral systems to educate women and provide effective care for both women and infants

Respiratory syncytial virus (RSV) attachment and nonstructural proteins modify the type I interferon response associated with suppressor of cytokine signaling (SOCS) proteins and IFN-stimulated gene-15 (ISG15)

Respiratory syncytial virus (RSV) is a major cause of severe lower airway disease in infants and young children, but no safe and effective RSV vaccine is yet available. Factors attributing to this problem are associated with an incomplete understanding of the mechanisms by which RSV modulates the host cell response to infection. In the present study, we investigate suppressor of cytokine signaling (SOCS)-1 and SOCS3 expression associated with the type I IFN and IFN-stimulated gene (ISG)-15 response following infection of mouse lung epithelial (MLE-15) cells with RSV or RSV mutant viruses lacking the G gene, or NS1 and NS2 gene deletions. Studies in MLE-15 cells are important as this cell line represents the distal bronchiolar and alveolar epithelium of mice, the most common animal model used to evaluate the host cell response to RSV infection, and exhibit morphologic characteristics of alveolar type II cells, a primary cell type targeted during RSV infection. These results show an important role for SOCS1 regulation of the antiviral host response to RSV infection, and demonstrate a novel role for RSV G protein manipulation of SOCS3 and modulation of ISG15 and IFNβ mRNA expression

The infrared imaging spectrograph (IRIS) for TMT: sensitivities and simulations

We present sensitivity estimates for point and resolved astronomical sources for the current design of the InfraRed Imaging Spectrograph (IRIS) on the future Thirty Meter Telescope (TMT). IRIS, with TMT's adaptive optics system, will achieve unprecedented point source sensitivities in the near-infrared (0.84 - 2.45 {\mu}m) when compared to systems on current 8-10m ground based telescopes. The IRIS imager, in 5 hours of total integration, will be able to perform a few percent photometry on 26 - 29 magnitude (AB) point sources in the near-infrared broadband filters (Z, Y, J, H, K). The integral field spectrograph, with a range of scales and filters, will achieve good signal-to-noise on 22 - 26 magnitude (AB) point sources with a spectral resolution of R=4,000 in 5 hours of total integration time. We also present simulated 3D IRIS data of resolved high-redshift star forming galaxies (1 < z < 5), illustrating the extraordinary potential of this instrument to probe the dynamics, assembly, and chemical abundances of galaxies in the early universe. With its finest spatial scales, IRIS will be able to study luminous, massive, high-redshift star forming galaxies (star formation rates ~ 10 - 100 M yr-1) at ~100 pc resolution. Utilizing the coarsest spatial scales, IRIS will be able to observe fainter, less massive high-redshift galaxies, with integrated star formation rates less than 1 M yr-1, yielding a factor of 3 to 10 gain in sensitivity compared to current integral field spectrographs. The combination of both fine and coarse spatial scales with the diffraction-limit of the TMT will significantly advance our understanding of early galaxy formation processes and their subsequent evolution into presentday galaxies.Comment: SPIE Astronomical Instrumentation 201

Respiratory syncytial virus (RSV) attachment and nonstructural proteins modify the type I interferon response associated with suppressor of cytokine signaling (SOCS) proteins and IFN-stimulated gene-15 (ISG15)

Respiratory syncytial virus (RSV) is a major cause of severe lower airway disease in infants and young children, but no safe and effective RSV vaccine is yet available. Factors attributing to this problem are associated with an incomplete understanding of the mechanisms by which RSV modulates the host cell response to infection. In the present study, we investigate suppressor of cytokine signaling (SOCS)-1 and SOCS3 expression associated with the type I IFN and IFN-stimulated gene (ISG)-15 response following infection of mouse lung epithelial (MLE-15) cells with RSV or RSV mutant viruses lacking the G gene, or NS1 and NS2 gene deletions. Studies in MLE-15 cells are important as this cell line represents the distal bronchiolar and alveolar epithelium of mice, the most common animal model used to evaluate the host cell response to RSV infection, and exhibit morphologic characteristics of alveolar type II cells, a primary cell type targeted during RSV infection. These results show an important role for SOCS1 regulation of the antiviral host response to RSV infection, and demonstrate a novel role for RSV G protein manipulation of SOCS3 and modulation of ISG15 and IFNβ mRNA expression