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6,130 results on '"Davis, Andrew"'

5. Defending Large Language Models Against Attacks With Residual Stream Activation Analysis

Author

Kawasaki, Amelia, Davis, Andrew, and Abbas, Houssam

Subjects
Computer Science - Cryptography and Security, Computer Science - Machine Learning
Abstract

The widespread adoption of Large Language Models (LLMs), exemplified by OpenAI's ChatGPT, brings to the forefront the imperative to defend against adversarial threats on these models. These attacks, which manipulate an LLM's output by introducing malicious inputs, undermine the model's integrity and the trust users place in its outputs. In response to this challenge, our paper presents an innovative defensive strategy, given white box access to an LLM, that harnesses residual activation analysis between transformer layers of the LLM. We apply a novel methodology for analyzing distinctive activation patterns in the residual streams for attack prompt classification. We curate multiple datasets to demonstrate how this method of classification has high accuracy across multiple types of attack scenarios, including our newly-created attack dataset. Furthermore, we enhance the model's resilience by integrating safety fine-tuning techniques for LLMs in order to measure its effect on our capability to detect attacks. The results underscore the effectiveness of our approach in enhancing the detection and mitigation of adversarial inputs, advancing the security framework within which LLMs operate.

Published
2024

6. SPHEREx: NASA's Near-Infrared Spectrophotmetric All-Sky Survey

Author

Crill, Brendan P., Werner, Michael, Akeson, Rachel, Ashby, Matthew, Bleem, Lindsey, Bock, James J., Bryan, Sean, Burnham, Jill, Byunh, Joyce, Chang, Tzu-Ching, Chiang, Yi-Kuan, Cook, Walter, Cooray, Asantha, Davis, Andrew, Doré, Olivier, Dowell, C. Darren, Dubois-Felsmann, Gregory, Eifler, Tim, Faisst, Andreas, Habib, Salman, Heinrich, Chen, Heitmann, Katrin, Heaton, Grigory, Hirata, Christopher, Hristov, Viktor, Hui, Howard, Jeong, Woong-Seob, Kang, Jae Hwan, Kecman, Branislav, Kirkpatrick, J. Davy, Korngut, Phillip M., Krause, Elisabeth, Lee, Bomee, Lisse, Carey, Masters, Daniel, Mauskopf, Philip, Melnick, Gary, Miyasaka, Hiromasa, Nayyeri, Hooshang, Nguyen, Hien, Öberg, Karin, Padin, Steve, Paladini, Roberta, Pourrahmani, Milad, Pyo, Jeonghyun, Smith, Roger, Song, Yong-Seong, Symons, Teresa, Teplitz, Harry, Tolls, Volker, Unwin, Steve, Windhorst, Rogier, Yang, Yujin, and Zemcov, Michael

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer, is a NASA MIDEX mission planned for launch in 2024. SPHEREx will carry out the first all-sky spectral survey at wavelengths between 0.75 micron and 5 micron with spectral resolving power ~40 between 0.75 and 3.8 micron and ~120 between 3.8 and 5 micron At the end of its two-year mission, SPHEREx will provide 0.75-to-5 micron spectra of each 6.2"x6.2" pixel on the sky - 14 billion spectra in all. This paper updates an earlier description of SPHEREx presenting changes made during the mission's Preliminary Design Phase, including a discussion of instrument integration and test and a summary of the data processing, analysis, and distribution plans.

Published
2024
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14. Flecainide Is Associated With a Lower Incidence of Arrhythmic Events in a Large Cohort of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia.

Author

Bergeman, Auke, Lieve, Krystien, Kallas, Dania, Bos, J, Rosés I Noguer, Ferran, Denjoy, Isabelle, Zorio, Esther, Kammeraad, Janneke, Peltenburg, Puck, Tobert, Katie, Aiba, Takeshi, Atallah, Joseph, Drago, Fabrizio, Batra, Anjan, Brugada, Ramon, Borggrefe, Martin, Clur, Sally-Ann, Cox, Moniek, Davis, Andrew, Dhillon, Santokh, Etheridge, Susan, Fischbach, Peter, Franciosi, Sonia, Haugaa, Kristina, Horie, Minoru, Johnsrude, Christopher, Kane, Austin, Krause, Ulrich, Kwok, Sit-Yee, LaPage, Martin, Ohno, Seiko, Probst, Vincent, Roberts, Jason, Robyns, Tomas, Sacher, Frederic, Semsarian, Christopher, Skinner, Jonathan, Swan, Heikki, Tavacova, Terezia, Tisma-Dupanovic, Svjetlana, Tfelt-Hansen, Jacob, Yap, Sing-Chien, Kannankeril, Prince, Leenhardt, Antoine, Till, Janice, Sanatani, Shubhayan, Tanck, Michael, Ackerman, Michael, Wilde, Arthur, and van der Werf, Christian

Subjects
catecholaminergic polymorphic ventricular tachycardia, sudden cardiac death, ventricular arrhythmias, Female, Humans, Adolescent, Male, Flecainide, Incidence, Cross-Over Studies, Tachycardia, Ventricular, Adrenergic beta-Antagonists, Defibrillators, Implantable, Death, Sudden, Cardiac
Abstract

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P=0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P=0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P

Published
2023

15. Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample.

Author

Yokoyama, Tetsuya, Wadhwa, Meenakshi, Iizuka, Tsuyoshi, Rai, Vinai, Gautam, Ikshu, Hibiya, Yuki, Masuda, Yuki, Haba, Makiko, Fukai, Ryota, Hines, Rebekah, Phelan, Nicole, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel, Amari, Sachiko, Amelin, Yuri, Bajo, Ken-Ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard, Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew, Di Rocco, Tommaso, Fujiya, Wataru, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary, Ichida, Kiyohiro, Ireland, Trevor, Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko, Kitajima, Koki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander, Liu, Ming-Chang, McKeegan, Kevin, Morita, Mayu, Motomura, Kazuko, Moynier, Frédéric, Nakai, Izumi, Nagashima, Kazuhide, Nguyen, Ann, Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara, Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Walker, Richard, Yamashita, Katsuyuki, Yoneda, Shigekazu, Young, Edward, Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-Ichiro, Yoshikawa, Makoto, Tachibana, Shogo, Yurimoto, Hisayoshi, and Yin, Qing-Zhu

Abstract

Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between 54Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred [Formula: see text] after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water.

Published
2023

16. Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu.

Author

Nguyen, Ann, Mane, Prajkta, Keller, Lindsay, Piani, Laurette, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel, Amari, Sachiko, Amelin, Yuri, Bajo, Ken-Ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard, Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew, Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko, Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary, Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor, Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko, Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander, Liu, Ming-Chang, Masuda, Yuki, McKeegan, Kevin, Morita, Mayu, Motomura, Kazuko, Moynier, Frédéric, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Qin, Liping, Russell, Sara, Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard, Yamashita, Katsuyuki, Yokoyama, Tetsuya, Yoneda, Shigekazu, Young, Edward, Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-Ichiro, Yoshikawa, Makoto, Tachibana, Shogo, Yurimoto, Hisayoshi, and Yin, Qing-Zhu

Subjects
Carbon, Solar System, Meteoroids, Silicates
Abstract

Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugus rubble pile origin.

Published
2023

18. Understanding the Conceptions of Engineering in Early Elementary Students

Author

Lampley, Sandra A., Dyess, Sarah Roller, Benfield, Michael P. J., Davis, Andrew M., Gholston, Sampson E., Dillihunt, Monica L., and Turner, Matthew W.

Abstract

There is a demand for more STEM professionals. Early elementary students' conceptions about engineering can influence whether or not they explore STEM career paths and ultimately select an engineering career. This study examined the conceptions elementary students have regarding the work that engineers perform. The research questions were the following: (1) what images do early elementary students associate with engineering and engineers, (2) do these associations vary from grade to grade, (3) are there gendered differences in these associations, and (4) how do the associations from this sample compare with the associations from the broader (grades one--five) Cunningham, Lachapelle, and Lindgren-Steider (2005) sample? Survey data from 1811 students in grades one-three were analyzed by comparison analysis and cluster analysis and then compared to the initial Cunningham et al. (2005) study. The results indicate two ways elementary students envision engineering: (a) creating designs or collecting and analyzing data, and (b) utilizing equipment to build and improve things. Comparison with the Cunningham et al. (2005) study suggests that there may be shifts in the way elementary students perceive engineering. Since these shifts could be attributed to a variety of factors, future work that determines what learning experiences might be contributing to students' conceptions about engineering is recommended.

Published
2022

19. Quantum chaos and phase transition in the Yukawa-SYK model

Author

Davis, Andrew and Wang, Yuxuan

Subjects
Condensed Matter - Strongly Correlated Electrons, High Energy Physics - Theory
Abstract

We analyze the quantum chaotic behavior of the Yukawa-SYK model as a function of filling and temperature, which describes random Yukawa interactions between $N$ complex fermions and $M$ bosons in zero spatial dimensions, for both the non-Fermi liquid and insulating states at finite temperature and chemical potential. We solve the ladder equations for the out-of-time-order correlator (OTOC) for both the bosons and fermions. Despite the appearance of the chemical potential in the Hamiltonian, which explicitly introduces an additional energy scale, the OTOCs for the fermions and bosons in the non-Fermi liquid state turn out to be unaffected, and the Lyapunov exponents that diagnose chaos remain maximal. As the chemical potential increases, the system is known to experience a first-order transition from a critical phase to a gapped insulating phase. We postulate that the boundary of the region in parameter space where each phase is (meta)stable coincides with the curve on which the Lyapunov exponent is maximal. By calculating the exponent in the insulating phase and comparing to numerical results on the boundaries of stability, we show that this is plausible.

Published
2022
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20. Presolar Silicon Carbide Grains of Types Y and Z: Their Strontium and Barium Isotopic Compositions and Stellar Origins

Author

Liu, Nan, Stephan, Thomas, Cristallo, Sergio, Vescovi, Diego, Gallino, Roberto, Nittler, Larry R., Alexander, Conel M. O' D., and Davis, Andrew M.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

We report the Sr and Ba isotopic compositions of 18 presolar SiC grains of types Y (11) and Z (7), rare types commonly argued to have formed in lower-than-solar metallicity asymptotic giant branch (AGB) stars. We find that the Y and Z grains show higher 88Sr/87Sr and more variable 138Ba/136Ba ratios than mainstream (MS) grains. According to FRANEC Torino AGB models, the Si, Sr, and Ba isotopic compositions of our Y and Z grains can be consistently explained if the grains came from low mass AGB stars with 0.15 Zsun <= Z < 1.00 Zsun, in which the 13C neutron exposure for the slow neutron-capture process is greatly reduced with respect to that required by MS grains for a 1.0 Z8 AGB star. This scenario is in line with the previous finding based on Ti isotopes, but it fails to explain the indistinguishable Mo isotopic compositions of MS, Y, and Z grains., Comment: Accepted by EPJA

Published
2022
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21. Presolar stardust in asteroid Ryugu

Author

Barosch, Jens, Nittler, Larry R., Wang, Jianhua, Alexander, Conel M. O'D., De Gregorio, Bradley T., Engrand, Cécile, Kebukawa, Yoko, Nagashima, Kazuhide, Stroud, Rhonda M., Yabuta, Hikaru, Abe, Yoshinari, Aléon, Jérôme, Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bejach, Laure, Bizzarro, Martin, Bonal, Lydie, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Cody, George D., Dartois, Emmanuel, Dauphas, Nicolas, Davis, Andrew M., Dazzi, Alexandre, Deniset-Besseau, Ariane, Di Rocco, Tommaso, Duprat, Jean, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hashiguchi, Minako, Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Ito, Motoo, Itoh, Shoichi, Kamide, Kanami, Kawasaki, Noriyuki, Kilcoyne, A. L. David, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Komatsu, Mutsumi, Krot, Alexander N., Liu, Ming-Chang, Martins, Zita, Masuda, Yuki, Mathurin, Jérémie, McKeegan, Kevin D., Montagnac, Gilles, Morita, Mayu, Mostefaoui, Smail, Motomura, Kazuko, Moynier, Frédéric, Nakai, Izumi, Nguyen, Ann N., Ohigashi, Takuji, Okumura, Taiga, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Quirico, Eric, Remusat, Laurent, Russell, Sara S., Sakamoto, Naoya, Sandford, Scott A., Schönbächler, Maria, Shigenaka, Miho, Suga, Hiroki, Tafla, Lauren, Takahashi, Yoshio, Takeichi, Yasuo, Tamenori, Yusuke, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Verdier-Paoletti, Maximilien, Wada, Sohei, Wadhwa, Meenakshi, Wakabayashi, Daisuke, Walker, Richard J., Yamashita, Katsuyuki, Yamashita, Shohei, Yin, Qing-Zhu, Yokoyama, Tetsuya, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nakazawa, Satoru, Nishimura, Masahiro, Okada, Tatsuaki, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yada, Toru, Yogata, Kasumi, Yoshikawa, Makoto, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Tachibana, Shogo, and Yurimoto, Hisayoshi

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are 4.8$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm for SiC grains and 11$^{+5}_{-3}$ ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23 $^{+7}_{-6}$ ppm SiC and 9.0$^{+5.3}_{-4.6}$ ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material., Comment: 12 pages, 3 figures, 2 tables. Published in ApJL

Published
2022
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22. Building Confidence: Engaging Students through 3D Printing in Biology Courses

Author

Guenther, Courtney, Hayes, Matthew, Davis, Andrew, and Stern, Matthew

Abstract

3D printing is a widely used technology in a number of STEM fields and can be incorporated into undergraduate education in order to engage students in active learning. Using the Technological Pedagogical Content Knowledge (TPACK) framework, this study examined student perceptions of completing 3D printing of a physical model in two different Biology courses, Anatomy and Physiology and Molecular Biology. Students completed surveys before and after engaging in a semester-long 3D printing project. Demographic information was also collected in order to assess student perceptions based on race and sex. Students reported increased confidence with 3D printing technology after completing their projects, and this effect occurred similarly across race and sex. Student attitudes towards their 3D printing experience were overwhelmingly positive, with general interest and excitement being the most common themes. These results suggest that 3D printing projects can be successfully implemented in undergraduate courses and generate positive student outcomes. Engaging women and underrepresented minority students with 3D printing technology may have significant implications for retention of these students in STEM programs.

Published
2021

23. ParticLS: Object-oriented software for discrete element methods and peridynamics

Author

Davis, Andrew D., West, Brendan A., Frisch, Nathanael J., O'Connor, Devin T., and Parno, Matthew D.

Subjects
Computer Science - Mathematical Software, Computer Science - Computational Engineering, Finance, and Science
Abstract

ParticLS (\emph{Partic}le \emph{L}evel \emph{S}ets) is a software library that implements the discrete element method (DEM) and meshfree methods. ParticLS tracks the interaction between individual particles whose geometries are defined by level sets capable of capturing complex shapes. These particles either represent rigid bodies or material points within a continuum. Particle-particle interactions using various contact laws numerically approximate solutions to energy and mass conservation equations, simulating rigid body dynamics or deformation/fracture. By leveraging multiple contact laws, ParticLS can simulate interacting bodies that deform, fracture, and are composed of many particles. In the continuum setting, we numerically solve the peridynamic equations -- integro-differential equations capable of modeling objects with discontinuous displacement fields and complex fracture dynamics. We show that the discretized peridynamic equations can be solved using the same software infrastructure that implements the DEM. Therefore, we design a unique software library where users can easily add particles with arbitrary geometries and new contact laws that model either rigid-body interaction or peridynamic constitutive relationships. We demonstrate ParticLS' versatility on test problems meant to showcase features applicable to a broad selection of fields such as tectonics, granular media, multiscale simulations, glacier calving, and sea ice.

Published
2022
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24. Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2

Author

Kawasaki, Noriyuki, Nagashima, Kazuhide, Sakamoto, Naoya, Matsumoto, Toru, Bajo, Ken-ichi, Wada, Sohei, Igami, Yohei, Miyake, Akira, Noguchi, Takaaki, Yamamoto, Daiki, Russell, Sara S, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel M O’D, Amari, Sachiko, Amelin, Yuri, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W, Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M, Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K, Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R, Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R, Ishikawa, Akira, Ito, Motoo, Itoh, Shoichi, Kita, Noriko T, Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N, Liu, Ming-Chang, Masuda, Yuki, McKeegan, Kevin D, Morita, Mayu, Motomura, Kazuko, Moynier, Frédéric, Nakai, Izumi, Nguyen, Ann, Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wadhwa, Meenakshi, Walker, Richard J, Yamashita, Katsuyuki, Yin, Qing-Zhu, Yokoyama, Tetsuya, Yoneda, Shigekazu, Young, Edward D, Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Subjects
Earth Sciences, Physical Sciences, Space Sciences, Geology, Prevention
Abstract

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16O-rich (associated with refractory inclusions) and 16O-poor (associated with chondrules). Both the 16O-rich and 16O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16O-rich to 16O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

Published
2022

27. Governance

Author

Wallestad, Anne, primary, Folkedal, Joy, additional, and Davis, Andrew, additional

Published
2023
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28. Histone chaperone HIRA, promyelocytic leukemia protein, and p62/SQSTM1 coordinate to regulate inflammation during cell senescence

Author

Dasgupta, Nirmalya, Lei, Xue, Shi, Christina Huan, Arnold, Rouven, Teneche, Marcos G., Miller, Karl N., Rajesh, Adarsh, Davis, Andrew, Anschau, Valesca, Campos, Alexandre R., Gilson, Rebecca, Havas, Aaron, Yin, Shanshan, Chua, Zong Ming, Liu, Tianhui, Proulx, Jessica, Alcaraz, Michael, Rather, Mohammed Iqbal, Baeza, Josue, Schultz, David C., Yip, Kevin Y., Berger, Shelley L., and Adams, Peter D.

Published
2024
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29. Pyrrhotites in asteroid 162173 Ryugu: Records of the initial changes on their surfaces with aqueous alteration

Author

Yui, Hiroharu, Urashima, Shu-hei, Onose, Morihiko, Morita, Mayu, Komatani, Shintaro, Nakai, Izumi, Abe, Yoshinari, Terada, Yasuko, Homma, Hisashi, Motomura, Kazuko, Ichida, Kiyohiro, Yokoyama, Tetsuya, Nagashima, Kazuhide, Aléon, Jérôme, M. O’D. Alexander, Conel, Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Hoppe, Peter, Huss, Gary R., Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Krot, Sasha, Liu, Ming-Chang, Masuda, Yuki, Moynier, Frédéric, Nguyen, Ann, Nittler, Larry, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Di Rocco, Tommaso, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2024
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32. Teaching the Holocaust in Jewish schools in England : a study into practice, perspectives and challenges

Author

Davis, Andrew Marc

Abstract

In 2009, the Institute of Education published the first empirical study into teaching the Holocaust in England's secondary schools. However, no specific research has been undertaken on Holocaust education in Jewish schools in England. My study examines provision of teaching about the Holocaust in such schools, exploring teachers' aims, pedagogical approaches and distinctive challenges in the Jewish school context. The research for this study used a three-phased approach: 1. Interviews with school leaders and desk-based research on the context in which schools operated. This provided a landscape of types of Jewish schools in England and information about whether and how they taught about the Holocaust. 2. The sample narrowed to only those in which the Holocaust was taught. Data was initially gathered via an online survey of teachers to collect more detailed information. Follow-up interviews were also conducted. 3. The sample was narrowed to a good cross-section of four schools. In-depth teacher interviews were conducted in each school with two members of staff who taught about the Holocaust. Interviews explored differences and complexities uncovered in previous phases and illuminated issues raised by my research questions. This study provides insights into the Jewish secondary schools' landscape and explains how ethos and practice affected curriculum priorities. It revealed that not all Jewish schools teach about the Holocaust and differences exist between schools that do. Most students in Jewish schools received more Holocaust education than their peers in non-Jewish schools. A distinctive feature in most schools was Year 12 educational journeys to Poland, typically seen as the culmination of the schools' Holocaust education. This study concludes by highlighting elements of impressive practice of Holocaust education in Jewish schools in England. It offers recommendations for how Holocaust education may be improved and how exemplary practice may be shared across all schools.

Published
2022

34. Interplay between ESR1/PIK3CA codon variants, oncogenic pathway alterations and clinical phenotype in patients with metastatic breast cancer (MBC): comprehensive circulating tumor DNA (ctDNA) analysis

Author

Gerratana, Lorenzo, Davis, Andrew A., Velimirovic, Marko, Clifton, Katherine, Hensing, Whitney L., Shah, Ami N., Dai, Charles S., Reduzzi, Carolina, D’Amico, Paolo, Wehbe, Firas, Medford, Arielle, Wander, Seth A., Gradishar, William J., Behdad, Amir, Puglisi, Fabio, Ma, Cynthia X., Bardia, Aditya, and Cristofanilli, Massimo

Published
2023
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37. Graph-theoretic algorithms for Kolmogorov operators: Approximating solutions and their gradients in elliptic and parabolic problems on manifolds

Author

Davis, Andrew D. and Giannakis, Dimitrios

Subjects
Mathematics - Numerical Analysis
Abstract

We employ kernel-based approaches that use samples from a probability distribution to approximate a Kolmogorov operator on a manifold. The self-tuning variable-bandwidth kernel method [Berry & Harlim, Appl. Comput. Harmon. Anal., 40(1):68--96, 2016] computes a large, sparse matrix that approximates the differential operator. Here, we use the eigendecomposition of the discretization to (i) invert the operator, solving a differential equation, and (ii) represent gradient vector fields on the manifold. These methods only require samples from the underlying distribution and, therefore, can be applied in high dimensions or on geometrically complex manifolds when spatial discretizations are not available. We also employ an efficient $k$-$d$ tree algorithm to compute the sparse kernel matrix, which is a computational bottleneck.

Published
2021

38. Comparison of Verbal Performance of Children with Autism Spectrum Disorder on the WISC-V

Author

Dale, Brittany A., Finch, W. Holmes, Shellabarger, Kassie A. R., and Davis, Andrew

Abstract

Children with autism spectrum disorder (ASD) display variable verbal cognitive profiles despite a historical requirement for a language delay in autistic disorder. This study compared the Verbal Comprehension Index (VCI) to the newly created ancillary index score, the Verbal Expanded Crystallized Index (VECI) of the Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V) in a group of children with ASD. Using the ASD sample from the standardization data of the WISC-V, results indicated the VCI and VECI were significantly different for the ASD group but not for the matched controls. Follow up analysis of the ASD group revealed the VCI and VECI were significantly different for those with language impairment but not for those without language impairment. Psychologists should consider administering all verbal subtests of the WISC-V to children with ASD given the VECI may better capture the language impairment seen in this population.

Published
2022
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40. Pervasive aqueous alteration in the early Solar System revealed by potassium isotopic variations in Ryugu samples and carbonaceous chondrites

Author

Hu, Yan, Moynier, Frédéric, Dai, Wei, Paquet, Marine, Yokoyama, Tetsuya, Abe, Yoshinari, Aléon, Jérôme, Alexander, Conel M. O'D., Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Koki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N., Liu, Ming-Chang, Masuda, Yuki, Morita, Mayu, Motomura, Kazuko, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nguyen, Ann, Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2024
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41. A multitiered analysis platform for genome sequencing: Design and initial findings of the Australian Genomics Cardiovascular Disorders Flagship

Author

Ades, Lesley, Enriquez, Annabel, McLean, Alison, Smyth, Renee, Alankarage, Dimithu, Fatkin, Diane, McNamara, James, Soka, Magdalena, Morgan almog, Fear, Vanessa, Medi, Caroline, Stark, Zornitza, Al-Shinnag, Mohammad, Fine, Miriam, Metke, Alejandro, Sy, Raymond, Atherton, John J., Finlay, Keri, Milnes, Di, Tang, Dotti, Austin, Rachel, Garza, Denisse, Milward, Michael, Taylor, Jessica, Bagnall, Richard D., Giannoulatou, Eleni, Morrish, Ansley, Taylor, Shelby, Barnett, Chris, Gongolidis, Laura, Morwood, Jim, Tchan, Michel, Blue, Gillian M., Gray, Belinda, Mountain, Helen, Thompson, Tina, Bodek, Simon, Greer, Cassie, Mowat, David, Thorpe, Jordan, Boggs, Kirsten, Haan, Eric, Ng, Chai-Ann, Trainer, Alison, Bogwitz, Michael, Haas, Mathilda, Nowak, Natalie, Trivedi, Gunjan, Boughtwood, Tiffany, Hanna, Bernadette, Martinez, Noelia Nunez, Valente, Giulia, Bray, Alessandra, Harvey, Richard, Ohanian, Monique, van Spaendonck-Zwarts, Karin, Brion, Marie-Jo, Hayward, Janette, O’Sullivan, Sinead, Vandenberg, Jamie, Brown, Jaye, Herrera, Carmen, Overkov, Angela, Verma, Kunal, Richardson, Rob Bryson, Hill, Adam, Pachter, Nicholas, Vidgen, Miranda, Burnett, Leslie, Hollingsworth, Georgie, Patel, Chirag, Vohra, Jitendra, Burns, Charlotte, Hollway, Georgina, Perrin, Mark, Waddel-Smith, Kathryn, Cao, Michelle, Horton, Ari E., Perry, Matthew, Wallis, Mathew, Carr, Will, Howting, Denise, Pflaumer, Andreas, Weintraub, Robert G., Casauria, Sarah, Ingles, Jodie, Phillips, Peta, Wilson, Meredith, Chalinor, Heather, Isbister, Joanne, Phuong, Thuan, Winlaw, David, Chang, Yuchen, Jackson, Matilda, Pope-Couston, Rachel, Worgan, Lisa, Chapman, Gavin, James, Paul, Poplawski, Nicola K., Wornham, Linda, Charitou, Theosodia, Jane-Pantaleo, Sarah, Punni, Preeti, Wu, Kathy, Chong, Belinda, Johnson, Renee, Quinn, Michael C.J., Yeates, Laura, Collins, Felicity, Kelly, Andrew, Quinn, Michael, Zentner, Dominica, Correnti, Gemma, King-Smith, Sarah, Rajagopalan, Sulekha, Cox, Kathy, Kirk, Edwin, Raju, Hariharan, Cunningham, Fiona, Kummerfeld, Sarah, Rath, Emma M., Das, Debjani, Lassman, Timo, Regan, Matthew, Davis, Jason, Lipton, Jonathon, Rogers, Jonathan, Davis, Andrew, Lunke, Sebastian, Ryan, Mark, De Fazio, Paul, Macciocca, Ivan, Sandaradura, Sarah, de Silva, Michelle, MacIntyre, Paul, Schonrock, Nicole, Den Elzen, Nicola, Madelli, Evanthia O., Scuffham, Paul, Devery, Sophie, Mallawaarachchi, Amali, Semsarian, Chris, Dobbins, Julia, Mansour, Julia, Sherburn, Isabella, Dunwoodie, Sally L., Martin, Ellenore, Sherlock, Mary-Clare, Dwyer, Nathan, Mathew, Jacob, Singer, Emma, Elbracht-Leong, Stefanie, Mattiske, Tessa, Smerdon, Carla, Elliott, David, McGaughran, Julie, Smith, Janine, Brown, Jaye S., Haas, Matilda, and Pantaleo, Sarah-Jane

Published
2024
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42. Phase diagram of the spin-1/2 Yukawa-SYK model: Non-Fermi liquid, insulator, and superconductor

Author

Wang, Wei, Davis, Andrew, Pan, Gaopei, Wang, Yuxuan, and Meng, Zi Yang

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

We analyze the phase diagram of the Yukawa-Sachdev-Ye-Kitaev model, which describes complex fermions randomly interacting with real bosons via a Yukawa coupling, at finite temperatures and varying fermion density. In a recent work [Phys. Rev. Research 2, 033084 (2020)] it has been shown that, upon varying filling or chemical potential, there exists a first-order quantum phase transition between a non-Fermi liquid (nFL) phase and an insulating phase. Here we show that in such a model with time-reversal symmetry this quantum phase transition is preempted by a pairing phase that develops as a low-temperature instability. As a remnant of the would-be nFL-insulator transition, the superconducting critical temperature rapidly decreases beyond a certain chemical potential. On the other hand, depending on parameters the first-order quantum phase transition extend to finite-temperatures and terminate at a thermal critical point, beyond which the nFL and the insulator become the same phase, similar to that of the liquid-gas and metal-insulator transition in real materials. We determine the pairing phase boundary and the location of the thermal critical point via combined analytic and quantum Monte Carlo numeric efforts. Our results provide the model realization of the transition of nFL's towards superconductivity and insulating states, therefore offer a controlled platform for future investigations of the generic phase diagram that hosts nFL, insulator and superconductor and their phase transitions., Comment: 9 pages, 6 figures

Published
2021
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43. Region of Interest Densitometry Analysis of Descemet Membrane Endothelial Keratoplasty Dehiscence on Anterior Segment Optical Coherence Tomography

Author

Cheung, Albert Y, Kalina, Andrew, Im, Alex, Davis, Andrew R, Eslani, Medi, Hogge, Raymond L, and Yeu, Elizabeth

Subjects
Biomedical and Clinical Sciences, Ophthalmology and Optometry, Eye Disease and Disorders of Vision, Eye, Densitometry, Descemet Membrane, Descemet Stripping Endothelial Keratoplasty, Retrospective Studies, Tomography, Optical Coherence, Visual Acuity, densitometry, optical density, anterior segment optical coherence tomography, Descemet membrane endothelial keratoplasty, graft dehiscence, Biomedical Engineering, Opthalmology and Optometry, Ophthalmology and optometry
Abstract

PurposeTo evaluate a region of interest (ROI) method of analyzing anterior segment optical coherence tomography (AS-OCT) corneal densitometry (CD) in the setting of Descemet membrane endothelial keratoplasty (DMEK) dehiscence.MethodsRetrospective chart review of eyes that underwent (1) DMEK for Fuchs dystrophy (2) between 2018 to 2020 with (3) a partial DMEK dehiscence on AS-OCT, (4) involvement of only one side of the graft, (5) high-quality corneal AS-OCT scan, and (6) location of dehiscence within the central 5.5 mm of the cornea. Image analysis of the ROIs with ImageJ compared the total edematous area, mean stromal CD, and ratio of anterior-to-posterior (A/P) stromal CD for regions of DMEK dehiscence compared to the contralateral side with an attached DMEK graft. Control regions (with no dehiscence) and postdehiscence resolution images were also analyzed.ResultsSeventy sectors of the 21 images from 21 eyes with DMEK dehiscence were included. Compared to the contralateral side, regions of DMEK dehiscence had larger total areas (P < 0.0001), lower mean stromal CD (P = 0.0003), and higher A/P stromal CD (P < 0.0001). All control regions and postdehiscence resolution images did not show any significant differences compared to the contralateral sides.ConclusionsThis technique to analyze multiple ROIs on AS-OCT can be useful to evaluate CD of specific regions of corneal pathology. Lower mean stromal CD and higher A/P stromal CD may specify corneal edema.Translational relevanceAnalyzing CD via multiple specific ROIs may be more suitable than measuring the CD of the full cornea and has broader applications extending to other corneal pathologies.

Published
2021

44. Search for meteoritic GEMS I: Comparison of amorphous silicates in Paris and Acfer 094 chondrite matrices and in anhydrous chondritic interplanetary dust particles

Author

Ohtaki, Kenta K, Ishii, Hope A, Bradley, John P, Villalon, Krysten L, Davis, Andrew M, Stephan, Thomas, Bustillo, Karen C, and Ciston, Jim

Subjects
Earth Sciences, Geology, GEMS, GEMS-like, Amorphous silicates, Matrix, Paris, Acfer 094, TEM, STEM, EDS, EELS, IDPs, Geochemistry, Physical Geography and Environmental Geoscience, Geochemistry & Geophysics
Abstract

Amorphous silicates in meteoritic samples are significant as potential surviving interstellar dust from the formation of the Solar System. Amorphous silicate-rich grains called GEMS, glass with embedded metal and sulfides, are abundant in anhydrous interplanetary dust particles and some ultracarbonaceous Antarctic micrometeorites that have high presolar grain abundances. Some GEMS within these objects have been confirmed to be presolar. GEMS-like material, consisting of amorphous silicate with opaque inclusions, has been identified in the matrices of some primitive meteorites. We use specialized thin specimen preparation and transmission electron microscopy methods to compare the GEMS-like material in Paris (CM) and Acfer 094 (ungrouped) chondrites with GEMS in anhydrous, chondritic interplanetary dust particles. Specifically, we compared the amorphous silicate morphology, degree of partial ordering, elemental composition and dominant iron oxidation state. We find that the amorphous silicates in the GEMS-like materials in Paris and Acfer 094 show incipient ordering and are Fe-rich and highly oxidized, while those in GEMS are fully amorphous, Fe-poor, and anhydrous. From examination of various formation routes for the amorphous silicates, we conclude that the GEMS-like material in Paris and Acfer 094 is not GEMS and that it is unlikely that GEMS-like material accreted as primary amorphous material that retained its original amorphous structure since accretion. We also conclude that the presence of GEMS-like amorphous silicates in chondrite matrix is not a reliable indicator for high degrees of primitivity or pristinity since even mild, complex alteration processes may significantly alter silicate structure. Finally, we propose searches for presolar amorphous silicates in chondrite matrix samples that have been precharacterized by transmission electron microscopy methods to enable direct comparisons of presolar amorphous silicate abundances.

Published
2021

45. Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis

Author

Paquet, Marine, Moynier, Frederic, Yokoyama, Tetsuya, Dai, Wei, Hu, Yan, Abe, Yoshinari, Aléon, Jérôme, O’D. Alexander, Conel M., Amari, Sachiko, Amelin, Yuri, Bajo, Ken-ichi, Bizzarro, Martin, Bouvier, Audrey, Carlson, Richard W., Chaussidon, Marc, Choi, Byeon-Gak, Dauphas, Nicolas, Davis, Andrew M., Di Rocco, Tommaso, Fujiya, Wataru, Fukai, Ryota, Gautam, Ikshu, Haba, Makiko K., Hibiya, Yuki, Hidaka, Hiroshi, Homma, Hisashi, Hoppe, Peter, Huss, Gary R., Ichida, Kiyohiro, Iizuka, Tsuyoshi, Ireland, Trevor R., Ishikawa, Akira, Ito, Motoo, Itoh, Shoichi, Kawasaki, Noriyuki, Kita, Noriko T., Kitajima, Kouki, Kleine, Thorsten, Komatani, Shintaro, Krot, Alexander N., Liu, Ming-Chang, Masuda, Yuki, McKeegan, Kevin D., Morita, Mayu, Motomura, Kazuko, Nakai, Izumi, Nagashima, Kazuhide, Nesvorný, David, Nguyen, Ann N., Nittler, Larry, Onose, Morihiko, Pack, Andreas, Park, Changkun, Piani, Laurette, Qin, Liping, Russell, Sara S., Sakamoto, Naoya, Schönbächler, Maria, Tafla, Lauren, Tang, Haolan, Terada, Kentaro, Terada, Yasuko, Usui, Tomohiro, Wada, Sohei, Wadhwa, Meenakshi, Walker, Richard J., Yamashita, Katsuyuki, Yin, Qing-Zhu, Yoneda, Shigekazu, Young, Edward D., Yui, Hiroharu, Zhang, Ai-Cheng, Nakamura, Tomoki, Naraoka, Hiroshi, Noguchi, Takaaki, Okazaki, Ryuji, Sakamoto, Kanako, Yabuta, Hikaru, Abe, Masanao, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Okada, Tatsuaki, Yada, Toru, Yogata, Kasumi, Nakazawa, Satoru, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yoshikawa, Makoto, Tachibana, Shogo, and Yurimoto, Hisayoshi

Published
2023
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46. Timing Calibration of the NuSTAR X-ray Telescope

Author

Bachetti, Matteo, Markwardt, Craig B., Grefenstette, Brian W., Gotthelf, Eric V., Kuiper, Lucien, Barret, Didier, Cook, W. Rick, Davis, Andrew, Fürst, Felix, Forster, Karl, Harrison, Fiona A., Madsen, Kristin K., Miyasaka, Hiromasa, Roberts, Bryce, Tomsick, John A., and Walton, Dominic J.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first focusing X-ray telescope in the hard X-ray (3-79 keV) band. Among the phenomena that can be studied in this energy band, some require high time resolution and stability: rotation-powered and accreting millisecond pulsars, fast variability from black holes and neutron stars, X-ray bursts, and more. Moreover, a good alignment of the timestamps of X-ray photons to UTC is key for multi-instrument studies of fast astrophysical processes. In this Paper, we describe the timing calibration of the NuSTAR mission. In particular, we present a method to correct the temperature-dependent frequency response of the on-board temperature-compensated crystal oscillator. Together with measurements of the spacecraft clock offsets obtained during downlinks passes, this allows a precise characterization of the behavior of the oscillator. The calibrated NuSTAR event timestamps for a typical observation are shown to be accurate to a precision of ~65 microsec., Comment: 13 pages, 10 figures. Comments welcome

Published
2020
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47. Rate-optimal refinement strategies for local approximation MCMC

Author

Davis, Andrew D., Marzouk, Youssef, Smith, Aaron, and Pillai, Natesh

Subjects
Statistics - Computation, Mathematics - Probability, Mathematics - Statistics Theory, 62C10, 62F15, F.2.1, G.3, G.4
Abstract

Many Bayesian inference problems involve target distributions whose density functions are computationally expensive to evaluate. Replacing the target density with a local approximation based on a small number of carefully chosen density evaluations can significantly reduce the computational expense of Markov chain Monte Carlo (MCMC) sampling. Moreover, continual refinement of the local approximation can guarantee asymptotically exact sampling. We devise a new strategy for balancing the decay rate of the bias due to the approximation with that of the MCMC variance. We prove that the error of the resulting local approximation MCMC (LA-MCMC) algorithm decays at roughly the expected $1/\sqrt{T}$ rate, and we demonstrate this rate numerically. We also introduce an algorithmic parameter that guarantees convergence given very weak tail bounds, significantly strengthening previous convergence results. Finally, we apply LA-MCMC to a computationally intensive Bayesian inverse problem arising in groundwater hydrology., Comment: 32 pages, 17 figures

Published
2020

48. Yukawa-SYK model and Self-tuned Quantum Criticality

Author

Pan, Gaopei, Wang, Wei, Davis, Andrew, Wang, Yuxuan, and Meng, Zi Yang

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract

Non-Fermi liquids (NFL) are a class of strongly interacting gapless fermionic systems without long-lived quasiparticle excitations. An important group of NFL model features itinerant fermions coupled to soft bosonic fluctuations near a quantum-critical point (QCP), and are widely believed to capture the essential physics of many unconventional superconductors. However numerically the direct observation of a canonical NFL behavior in such systems, characterized by a power-law form in the Green's function, has been elusive. Here we consider a Sachdev-Ye-Kitaev (SYK)-like model with random Yukawa interaction between critical bosons and fermions (dubbed Yukawa-SYK model). We show it is immune from minus-sign problem and hence can be solved exactly via large-scale quantum Monte Carlo simulation beyond the large-$N$ limit accessible to analytical approaches. Our simulation demonstrates the Yukawa-SYK model features "self-tuned quantum criticality", namely the system is critical independent of the bosonic bare mass. We put these results to test at finite $N$, and our unbiased numerics reveal clear evidence of these exotic quantum-critical NFL properties -- the power-law behavior in Green's function of fermions and bosons -- which propels the theoretical understanding of critical Planckian metals and unconventional superconductors., Comment: 13 pages, 8 figures

Published
2020
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