350 research outputs found
Stochastic self-assembly
We present methods for distributed self-assembly that utilize simple rule-of-thumb control and communication schemes providing probabilistic performance guarantees. These methods represents a staunch departure from existing approaches that require more sophisticated control and communication, but provide deterministic guarantees. In particular, we show that even under severe communication restrictions, any assembly described by an acyclic weighted graph can be assembled with a rule set that is linear in the number of nodes contained in the desired assembly graph. We introduce the concept of stochastic
stability to the self-assembly problem and show that stochastic stability of desirable configurations can be exploited to provide probabilistic performance guarantees for the process. Relaxation of the communication restrictions allows simple approaches giving deterministic guarantees. We establish a clear relationship between availability of communication and convergence properties. We consider Self-assembly tasks for the cases of many and few
agents as well as large and small assembly goals. We analyze sensitivity of the presented process to communication errors as well as ill-intentioned agents. We discuss convergence rates of the presented process and directions for improving them.M.S.Committee Chair: Jeff Shamma; Committee Member: Magnus Egerstedt; Committee Member: Martha Grove
Intrinsic symmetry groups of links with 8 and fewer crossings
We present an elementary derivation of the "intrinsic" symmetry groups for
knots and links of 8 or fewer crossings. The standard symmetry group for a link
is the mapping class group \MCG(S^3,L) or \Sym(L) of the pair .
Elements in this symmetry group can (and often do) fix the link and act
nontrivially only on its complement. We ignore such elements and focus on the
"intrinsic" symmetry group of a link, defined to be the image of
the natural homomorphism \MCG(S^3,L) \rightarrow \MCG(S^3) \cross \MCG(L).
This different symmetry group, first defined by Whitten in 1969, records
directly whether is isotopic to a link obtained from by permuting
components or reversing orientations.
For hyperbolic links both \Sym(L) and can be obtained using the
output of \texttt{SnapPea}, but this proof does not give any hints about how to
actually construct isotopies realizing . We show that standard
invariants are enough to rule out all the isotopies outside for all
links except , and where an additional construction
is needed to use the Jones polynomial to rule out "component exchange"
symmetries. On the other hand, we present explicit isotopies starting with the
positions in Cerf's table of oriented links which generate for each
link in our table. Our approach gives a constructive proof of the
groups.Comment: 72 pages, 66 figures. This version expands the original introduction
into three sections; other minor changes made for improved readabilit
Identifying the SN 2022acko progenitor with JWST
We report on analysis using the James Webb Space Telescope (JWST) to identify
a candidate progenitor star of the Type II-plateau supernova SN 2022acko in the
nearby, barred spiral galaxy NGC 1300. To our knowledge, our discovery
represents the first time JWST has been used to localize a progenitor system in
pre-explosion archival Hubble Space Telescope (HST) images. We astrometrically
registered a JWST NIRCam image from 2023 January, in which the SN was
serendipitously captured, to pre-SN HST F160W and F814W images from 2017 and
2004, respectively. An object corresponding precisely to the SN position has
been isolated with reasonable confidence. That object has a spectral energy
distribution (SED) and overall luminosity consistent with a single-star model
having an initial mass possibly somewhat less than the canonical 8 Msun
theoretical threshold for core collapse (although masses as high as 9 Msun for
the star are also possible); however, the star's SED and luminosity are
inconsistent with that of a super-asymptotic giant branch star which might be a
forerunner of an electron-capture SN. The properties of the progenitor alone
imply that SN 2022acko is a relatively normal SN II-P, albeit most likely a
low-luminosity one. The progenitor candidate should be confirmed with follow-up
HST imaging at late times, when the SN has sufficiently faded. This potential
use of JWST opens a new era of identifying SN progenitor candidates at high
spatial resolution.Comment: 8 pages, substantial changes from v1, to appear in MNRA
MFA15 (MFA 2015)
Catalogue of a culminating student exhibition held at the Mildred Lane Kemper Art Museum, May 1 - August 2, 2015 . Introduction / Heather Corcoran and Patricia Olynyk -- Diana Casanova / Emily J. Hanson -- Andrea M. Coates : in the operating theater / Stephanie Dering -- Margaux Crump -- Brandon Daniels -- Addoley Dzegede : do you prefer answers or truth? / Aaron Coleman -- Vita Eruhimovitz -- Carling Hale -- Amanda Helman -- Mike Helms / Ming Ying Hong -- Ming Ying Hong / Emily J. Hanson -- Sea A Joung / Ervin Malakaj -- Stephanie Kang / Jeremy Shipley -- Dayna Jean Kriz / Andrew Johnson -- Thomas Moore : you should move to the city / Nathaniel Rosenthalis -- Jacob Muldowney -- Laurel Panella / Garrett Clough -- Caitlin Penny -- On the bridge, between Juarez and El Paso / Eric Lyle Schultz -- Jeremy Shipley -- Emmeline Solomon -- Kellie Spano / Margaux Crump -- Michael Aaron Williams -- Austin R. Wolf : monumental labor / Adam Turl.https://openscholarship.wustl.edu/books/1015/thumbnail.jp
The Evolutionary and Phylogeographic History of Woolly Mammoths: A Comprehensive Mitogenomic Analysis
Near the end of the Pleistocene epoch, populations of the woolly mammoth (Mammuthus primigenius) were distributed across parts of three continents, from western Europe and northern Asia through Beringia to the Atlantic seaboard of North America. Nonetheless, questions about the connectivity and temporal continuity of mammoth populations and species remain unanswered. We use a combination of targeted enrichment and high-throughput sequencing to assemble and interpret a data set of 143 mammoth mitochondrial genomes, sampled from fossils recovered from across their Holarctic range. Our dataset includes 54 previously unpublished mitochondrial genomes and significantly increases the coverage of the Eurasian range of the species. The resulting global phylogeny confirms that the Late Pleistocene mammoth population comprised three distinct mitochondrial lineages that began to diverge ∼1.0-2.0 million years ago (Ma). We also find that mammoth mitochondrial lineages were strongly geographically partitioned throughout the Pleistocene. In combination, our genetic results and the pattern of morphological variation in time and space suggest that male-mediated gene flow, rather than large-scale dispersals, was important in the Pleistocene evolutionary history of mammoths
JWST Discovery of Dust Reservoirs in Nearby Type IIP Supernovae 2004et and 2017eaw
Supernova (SN) explosions have been sought for decades as a possible source
of dust in the Universe, providing the seeds of galaxies, stars, and planetary
systems. SN 1987A offers one of the most promising examples of significant SN
dust formation, but until the James Webb Space Telescope (JWST), instruments
have traditionally lacked the sensitivity at both late times (>1 yr
post-explosion) and longer wavelengths (i.e., >10 um) to detect analogous dust
reservoirs. Here we present JWST/MIRI observations of two historic Type IIP
SNe, 2004et and SN 2017eaw, at nearly 18 and 5 yr post-explosion, respectively.
We fit the spectral energy distributions as functions of dust mass and
temperature, from which we are able to constrain the dust geometry, origin, and
heating mechanism. We place a 90% confidence lower limit on the dust masses for
SNe 2004et and 2017eaw of >0.014 and >4e-4 M_sun, respectively. More dust may
exist at even colder temperatures or may be obscured by high optical depths. We
conclude dust formation in the ejecta to be the most plausible and consistent
scenario. The observed dust is radiatively heated to ~100-150 K by ongoing
shock interaction with the circumstellar medium. Regardless of the best fit or
heating mechanism adopted, the inferred dust mass for SN 2004et is the second
highest (next to SN 1987A) inferred dust mass in extragalactic SNe thus far,
promoting the prospect of SNe as potential significant sources of dust in the
Universe.Comment: 12 pages, 7 figures, submitting to MNRA
Building a Quantum Engineering Undergraduate Program
Contribution: A roadmap is provided for building a quantum engineering education program to satisfy U.S. national and international workforce needs.
Background: The rapidly growing quantum information science and engineering (QISE) industry will require both quantum-aware and quantum-proficient engineers at the bachelor\u27s level.
Research Question: What is the best way to provide a flexible framework that can be tailored for the full academic ecosystem?
Methodology: A workshop of 480 QISE researchers from across academia, government, industry, and national laboratories was convened to draw on best practices; representative authors developed this roadmap.
Findings: 1) For quantum-aware engineers, design of a first quantum engineering course, accessible to all STEM students, is described; 2) for the education and training of quantum-proficient engineers, both a quantum engineering minor accessible to all STEM majors, and a quantum track directly integrated into individual engineering majors are detailed, requiring only three to four newly developed courses complementing existing STEM classes; 3) a conceptual QISE course for implementation at any postsecondary institution, including community colleges and military schools, is delineated; 4) QISE presents extraordinary opportunities to work toward rectifying issues of inclusivity and equity that continue to be pervasive within engineering. A plan to do so is presented, as well as how quantum engineering education offers an excellent set of education research opportunities; and 5) a hands-on training plan on quantum hardware is outlined, a key component of any quantum engineering program, with a variety of technologies, including optics, atoms and ions, cryogenic and solid-state technologies, nanofabrication, and control and readout electronics
MFA09 (MFA 2009)
Catalogue of a culminating student exhibition held at the Mildred Lane Kemper Art Museum in 2009. Content includes A new paradigm / Carmon Colangelo -- Evolving practices / Patricia Olynyk -- Stephanie Barenz -- Carolyn Dawn Bendel -- Jacob Cruzen -- Rachel Ann Dennis -- Bryan Eaton -- Maya Escobar -- Meredith Foster -- Morgan Gehris -- Gina Grafos -- Stephen Hoskins -- Amelia Jones -- Hye Young Kim -- Anne Lindberg -- Goran Maric -- Kelda Martensen -- Erica L. Millspaugh -- Carianne Noga -- Joel Parker -- Rebecca C. Potts -- Shannon Randol -- Elaine Rickles -- Michael Kenneth Smith -- Dan Solberg -- Natalie Toney -- Glenn Tramantano -- Kathryn Trout -- J. Taylor Wallace.https://openscholarship.wustl.edu/books/1006/thumbnail.jp
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