Search

Your search keyword '"Hawkins, Aaron"' showing total 703 results
Start Over Author "Hawkins, Aaron"
703 results on '"Hawkins, Aaron"'

101. 3509098.pdf

Author

Rahman, Mahmudur, Stott, Matthew, Li, Yucheng, Hawkins, Aaron, and Schmidt, Holger

Abstract

Supplemental document

Published
2018
Full Text
View/download PDF

121. Frequency response of solid-state impact ionization multipliers.

Author

Beutler, Joshua L., Clauss, Carleton S., Johnson, Michael S., Hawkins, Aaron R., Jack, Mike D., Chapman, George R., and Kosai, Ken

Subjects
ELECTRON impact ionization, SOLID state electronics, IMPACT (Mechanics), ELECTRONIC amplifiers, HOT carriers, SCHOTTKY barrier diodes, SEMICONDUCTORS, MATERIALS science
Abstract

A study of the frequency response of solid-state impact ionization multipliers (SIMs) is presented that emphasizes the role of resistive and capacitive elements of the device to establish response limitations. SIMs are designed to amplify input currents from an external source through the impact ionization mechanism. An equivalent circuit model for the SIM is developed based on its current versus voltage characteristics, which is used to derive a frequency response model. Theoretical frequency response matches very closely to measured responses for first generation SIM devices constructed on p-type silicon epitaxial layers with nickel silicide Schottky contact injection points. Devices were measured using a photodiode as a current source under light intensities between 74 nA and 7.4 μA. These SIMs were shown to have a low frequency response that follows a KT/I relationship. Using an external photodiode with an effective capacitance of 6.8 pF, frequency response for a 1.8 μA input current was limited to 100 kHz. A large effective barrier resistance due to the Schottky contact and 12 kΩ space charge resistance dependent on device geometry dominate the response. Future SIM designs with higher frequency response will have to significantly lower both the input barrier resistance and space charge resistance. [ABSTRACT FROM AUTHOR]

Published
2007
Full Text
View/download PDF

122. Ancillary contributions of heterologous biotin protein ligase and carbonic anhydrase for CO2 incorporation into 3-hydroxypropionate by metabolically engineered Pyrococcus furiosus

Author

Lian, Hong, Zeldes, Benjamin M., Lipscomb, Gina L., Hawkins, Aaron. B., Han, Yejun, Loder, Andrew J., Nishiyama, Declan, Adams, Michael W.W., and Kelly, Robert M.

Subjects
Pyrococcus furiosus, Repressor Proteins, Metabolic Engineering, Escherichia coli Proteins, Sulfolobaceae, Carbon-Nitrogen Ligases, Lactic Acid, Carbon Dioxide, Protein Engineering, Article, Recombinant Proteins, Carbonic Anhydrases
Abstract

Acetyl-Coenzyme A carboxylase (ACC), malonyl-CoA reductase (MCR), and malonic semialdehyde reductase (MRS) convert HCO3− and acetyl-CoA into 3-hydroxypropionate (3HP) in the 3-hydroxypropionate/4-hydroxybutyrate carbon fixation cycle resident in the extremely thermoacidophilic archaeon Metallosphaera sedula. These three enzymes, when introduced into the hyperthermophilic archaeon Pyrococcus furiosus, enable production of 3HP from maltose and CO2. Sub-optimal function of ACC was hypothesized to be limiting for production of 3HP, so accessory enzymes carbonic anhydrase (CA) and biotin protein ligase (BPL) from M. sedula were produced recombinantly in Escherichia coli to assess their function. P. furiosus lacks a native, functional CA, while the M. sedula CA (Msed_0390) has a specific activity comparable to other microbial versions of this enzyme. M. sedula BPL (Msed_2010) was shown to biotinylate the β-subunit (biotin carboxyl carrier protein) of the ACC in vitro. Since the native BPLs in E. coli and P. furiosus may not adequately biotinylate the M. sedula ACC, the carboxylase was produced in P. furiosus by co-expression with the M. sedula BPL. The baseline production strain, containing only the ACC, MCR, and MSR, grown in a CO2-sparged bioreactor reached titers of approximately 40 mg/L 3HP. Strains in which either the CA or BPL accessory enzyme from M. sedula was added to the pathway resulted in improved titers, 120 or 370 mg/L, respectively. The addition of both M. sedula CA and BPL, however, yielded intermediate titers of 3HP (240 mg/L), indicating that the effects of CA and BPL on the engineered 3HP pathway were not additive, possible reasons for which are discussed. While further efforts to improve 3HP production by regulating gene dosage, improving carbon flux and optimizing bioreactor operation are needed, these results illustrate the ancillary benefits of accessory enzymes for incorporating CO2 into 3HP production in metabolically engineered P. furiosus, and hint at the important role that CA and BPL likely play in the native production of 3HP in M. sedula.

Published
2016

134. Broadband antireflective light-blocking layer using nanoparticle suspension in photoresist with high-resolution patterning.

Author

Hamblin, Matthew, Downing, Thane, Anderson, Sophia, Schmidt, Holger, and Hawkins, Aaron

Subjects
LIGHT transmission, OPTICAL devices, VISIBLE spectra, METAL nanoparticles, LIGHT scattering, SURFACE plasmon resonance
Abstract

Background: Many MEMS and optical sensor devices can benefit from layers that block transmission and suppress reflection of light across the visible spectrum. Because these devices can include complicated topography, many existing methods for depositing antireflective layers are difficult, impractical, or unusable. Aim: To create a light-blocking antireflective layer that works well with complicated MEMS and sensor devices, a layer should be made that is cheap, simple, and can be deposited and patterned with high resolution at low temperatures. Approach: Light blocking is achieved using an aluminum layer. Suppressing reflection is achieved by mixing aluminum oxide nanoparticles in photoresist to create a layer that partially absorbs and partially scatters light. Results: The combination of a layer of metal and a layer of nanoparticles and photoresist completely blocks transmission of light and significantly reduces reflections across the visible spectrum, particularly for shorter wavelengths. The layer is also patternable to sizes as small as a few microns with high resolution. Conclusion: By combining a metal layer and a layer of nanoparticles in photoresist, a simple, cheap, and effective light-blocking antireflective layer can be created that is compatible with planar devices with complex topography. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

135. Liquid-Core ARROW Platform for Organic Particle Detection

Author

Wall, Thomas and Hawkins, Aaron

Subjects
Astrophysics::Earth and Planetary Astrophysics
Abstract

The Liquid-Core ARROW platform, which can be used for single bioparticle detection, is outlined. The platform has been used successfully for detecting individual H3N2 viruses. These results clearly illustrate the ARROW platform’s capability to function as the go-to platform for a mission to Mars whose goal is to detect organic polymers in the soil. A presence of organic polymers would be a strong sign of past life on the planet. The ARROW is ideal for such a mission not only because of its capabilities in detection, but also because it is light weight, cheap to produce, and requires only low power to operate.

Published
2014

138. Ancillary contributions of heterologous biotin protein ligase and carbonic anhydrase for CO2incorporation into 3-hydroxypropionate by metabolically engineeredPyrococcus furiosus

Author

Lian, Hong, primary, Zeldes, Benjamin M., additional, Lipscomb, Gina L., additional, Hawkins, Aaron B., additional, Han, Yejun, additional, Loder, Andrew J., additional, Nishiyama, Declan, additional, Adams, Michael W.W., additional, and Kelly, Robert M., additional

Published
2016
Full Text
View/download PDF

145. Case of severe acute lupus myocarditis and multipleorgan failure.

Author

Hawkins, Aaron M., Jesuthasan, Lalith S. B., and Vardesh, Deepak L.

Abstract

We report a case of severe lupus myocarditis with rapid, acute deterioration to cardiogenic shock and multiorgan failure, highlighting the importance of early identification and treatment of acute presentations in patients with systemic lupus erythematosus. A 31-year-old woman with previously diagnosed subacute cutaneous lupus erythematosus initially presented with abdominal pain and frank per-rectal bleeding. She deteriorated rapidly with type 1 respiratory failure and acute kidney injury requiring dialysis secondary to acute cardiac failure with a prolonged intensive care unit admission, over a month. A significantly elevated troponin, global hypokinesia on echocardiogram and normal coronary artery angiogram and cardiac MRI lead to the diagnosis of acute lupus myocarditis as the cause for the cardiogenic shock. She was treated with high-dose corticosteroids and eventually made a full recovery, with cardiac function returning to normal. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

146. Antireflective light-blocking layers using a liquid top matte coating.

Author

Hamblin, Matthew, Downing, Thane, Anderson, Sophia, Hamilton, Erik, Doyoung Kim, and Hawkins, Aaron

Subjects
ANTIREFLECTIVE coatings, THIN film devices, LIGHT scattering, TRANSMISSION electron microscopes, LITHOGRAPHY
Abstract

Methods exist for the creation of antireflective thin film layers; however, many of these methods depend on the use of high temperatures, harsh chemical etches, or are made with difficult pattern materials, rendering them unusable for many applications. In addition, most methods of light blocking are specifically designed to increase light coupling and absorption in the substrate, making them incompatible with some applications that also require blocking transmission of light. A method of forming a simple, patternable light-blocking layer that drastically reduces both transmission and reflection of light without dependence on processes that could damage underlying structures using a light scattering matte coating over a partially antireflective thin film light-blocking layer is presented. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

147. The Planar Electrode Linear Ion Trap

Author

Hansen, Brett, Quist, Hannah, Hawkins, Aaron, and Austin, Daniel

Abstract

We present a linear type ion trap consisting of metal lines that are lithographically patterned onto two ceramic substrates. Trapping fields are realized by applying specific voltage potentials to each line. This arrangement allows miniaturization approaches that are immune to surface roughness issues and increased complexities of precision machining of electrode surfaces. We also present how these traps allow a thorough study of higher order multipoles and their effect on mass analyzer performance.

Published
2012

148. Planar Electrode Quadrupole Ion Traps

Author

Hansen, Brett, Quist, Hannah, Hawkins, Aaron, and Austin, Daniel

Abstract

We present a linear type ion trap consisting of metal lines that are lithographically patterned onto two ceramic substrates. Trapping fields are realized by applying specific voltage potentials to each line. This arrangement allows miniaturization approaches that are immune to surface roughness issues and increased complexities of precision machining of electrode surfaces. We also present how these traps allow a thorough study of higher order multipoles and their effect on mass analyzer performance.

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results