skip to main content


Search for: All records

Creators/Authors contains: "Grant, D."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available June 1, 2024
  2. Analysis of interdigitated transducers often relies on phenomenological models to approximate device electrical performance. While these approaches prove essential for signal processing applications, phenomenological models provide limited information on the device’s mechanical response and physical characteristics of the generated acoustic field. Finite element method modeling, in comparison, offers a robust platform to study the effects of the full device geometry on critical performance parameters of interdigitated transducer devices. In this study, we fabricate a surface acoustic wave resonator on semi-insulating GaAs [Formula: see text], which consists of an interdigitated transducer and acoustic mirror assembly. The device is subsequently modeled using fem software. A vector network analyzer is used to measure the experimental device scattering response, which compares well with the simulated results. The wave characteristics of the experimental device are measured by contact-mode atomic force microscopy, which validates the simulation’s mechanical response predictions. We further show that a computational parametric analysis can be used to optimize device designs for series resonance frequency, effective coupling coefficient, quality factor, and maximum acoustic surface displacement. 
    more » « less
  3. Abstract

    Four new isoorotamide (Io)‐containing PNA nucleobases have been designed for A−U recognition of double helical RNA. New PNA monomers were prepared efficiently and incorporated into PNA nonamers for binding A−U in a PNA:RNA2triplex. Isothermal titration calorimetry and UV thermal melting experiments revealed slightly improved binding affinity for singly modified PNA compared to known A‐binding nucleobases. Molecular dynamics simulations provided further insights into binding ofIobases in the triple helix. Together, the data revealed interesting insights into binding modes including the notion that three Hoogsteen hydrogen bonds are unnecessary for strong selective binding of an extended nucleobase. Cationic monomerIo8additionally gave the highest affinity observed for an A‐binding nucleobase to date. These results will help inform future nucleobase design toward the goal of recognizing any sequence of double helical RNA.

     
    more » « less
  4. Interdigitated transducer devices provide an advantageous platform to study stress-enhanced interfacial phenomena at elevated temperatures but require a thorough understanding of temperature-dependent material properties. In this study, the temperature dependence of the piezoelectric coefficient for gallium arsenide is determined from 22 ℃ to 177 ℃. Experimental scattering parameter responses are measured for a two-port surface acoustic wave resonator at different temperatures and piezoelectric coefficient values are extracted using a frequency-domain finite element method simulation. Device measurements are taken using an interdigitated transducer fabricated on semi-insulating GaAs(100), oriented in the 〈110〉 direction and device resonant frequencies are shown to decrease with increasing temperature. The experimental scattering response is used to reconcile the simulated scattering response and extract the 𝑒14 piezoelectric coefficient, which is shown to increase linearly with temperature. Using the extracted 𝑒14, surface acoustic wave analysis is completed to study the magnitude of bulk stress values and surface displacement over the experimental temperature range produced by a standing surface acoustic wave field. Surface displacement measurements are taken at room temperature using contact-mode AFM, which corroborate the simulation predictions. The modeling results demonstrate an interdigitated transducers potential as an experimental stage to study surface and bulk stress effects on temperature-sensitive phenomena. 
    more » « less
  5. null (Ed.)
    Interdigitated transducer devices provide an advantageous platform to study stress-enhanced interfacial phenomena at elevated temperatures but require a thorough understanding of temperature-dependent material properties. In this study, the temperature dependence of the piezoelectric coefficient for gallium arsenide is determined from 22 ℃ to 177 ℃. Experimental scattering parameter responses are measured for a two-port surface acoustic wave resonator at different temperatures and piezoelectric coefficient values are extracted using a frequency-domain finite element method simulation. Device measurements are taken using an interdigitated transducer fabricated on semi-insulating GaAs(100), oriented in the 〈110〉 direction and device resonant frequencies are shown to decrease with increasing temperature. The experimental scattering response is used to reconcile the simulated scattering response and extract the e_14 piezoelectric coefficient, which is shown to increase linearly with temperature. Using the extracted e_14, surface acoustic wave analysis is completed to study the magnitude of bulk stress values and surface displacement over the experimental temperature range produced by a standing surface acoustic wave field. Surface displacement measurements are taken at room temperature using contact-mode AFM, which corroborate the simulation predictions. The modeling results demonstrate an interdigitated transducers potential as an experimental stage to study surface and bulk stress effects on temperature-sensitive phenomena. 
    more » « less
  6. null (Ed.)
  7. null (Ed.)
  8. Abstract Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube neutrino data and a catalog containing more than 1000 core-collapse supernovae of types IIn and IIP and a sample of stripped-envelope supernovae. We search both for neutrino emission from individual supernovae as well as for combined emission from the whole supernova sample, through a stacking analysis. No significant spatial or temporal correlation of neutrinos with the cataloged supernovae was found. All scenarios were tested against the background expectation and together yield an overall p -value of 93%; therefore, they show consistency with the background only. The derived upper limits on the total energy emitted in neutrinos are 1.7 × 10 48 erg for stripped-envelope supernovae, 2.8 × 10 48 erg for type IIP, and 1.3 × 10 49 erg for type IIn SNe, the latter disfavoring models with optimistic assumptions for neutrino production in interacting supernovae. We conclude that stripped-envelope supernovae and supernovae of type IIn do not contribute more than 14.6% and 33.9%, respectively, to the diffuse neutrino flux in the energy range of about [ 10 3 –10 5 ] GeV, assuming that the neutrino energy spectrum follows a power-law with an index of −2.5. Under the same assumption, we can only constrain the contribution of type IIP SNe to no more than 59.9%. Thus, core-collapse supernovae of types IIn and stripped-envelope supernovae can both be ruled out as the dominant source of the diffuse neutrino flux under the given assumptions. 
    more » « less
    Free, publicly-accessible full text available May 1, 2024