6,652 research outputs found
Realization of a feedback controlled flashing ratchet
A flashing ratchet transports diffusive particles using a time-dependent,
asymmetric potential. Particle speed is predicted to increase when a feedback
algorithm based on particle positions is used. We have experimentally realized
such a feedback ratchet using an optical line trap, and observed that use of
feedback increases velocity by up to an order of magnitude. We compare two
different feedback algorithms for small particle numbers, and find good
agreement with simulations. We also find that existing algorithms can be
improved to be more tolerant to feedback delay times
Molecular control of stress transmission in the microtubule cytoskeleton
AbstractIn this article, we will summarize recent progress in understanding the mechanical origins of rigidity, strength, resiliency and stress transmission in the MT cytoskeleton using reconstituted networks formed from purified components. We focus on the role of network architecture, crosslinker compliance and dynamics, and molecular determinants of single filament elasticity, while highlighting open questions and future directions for this work
How Often Does the Best Team Win? A Unified Approach to Understanding Randomness in North American Sport
Statistical applications in sports have long centered on how to best separate signal (e.g. team talent) from random noise. However, most of this work has concentrated on a single sport, and the development of meaningful cross-sport comparisons has been impeded by the difficulty of translating luck from one sport to another. In this manuscript, we develop Bayesian state-space models using betting market data that can be uniformly applied across sporting organizations to better understand the role of randomness in game outcomes. These models can be used to extract estimates of team strength, the between-season, within-season, and game-to-game variability of team strengths, as well each team’s home advantage. We implement our approach across a decade of play in each of the National Football League (NFL), National Hockey League (NHL), National Basketball Association (NBA), and Major League Baseball (MLB), finding that the NBA demonstrates both the largest dispersion in talent and the largest home advantage, while the NHL and MLB stand out for their relative randomness in game outcomes. We conclude by proposing new metrics for judging competitiveness across sports leagues, both within the regular season and using traditional postseason tournament formats. Although we focus on sports, we discuss a number of other situations in which our generalizable models might be usefully applied
Indoor Mapping Drone
This project addresses the need for an autonomous indoor mapping system that will create a 3D map of an unknown physical environment in real time. The aerial system moves and avoids obstacles autonomously, without the need for human remote control or observation. An aerial system produces a map of an unknown indoor environment by transmitting data received from the aerial device’s sensors. The transmission occurs over a wireless channel from the aerial device to a remote server for processing and storage of the data. As the transmission is done in real time, the aerial system does not require hardware for storage of the map data. The remote system connected via the network will use the received information from the aerial device to create and display a 3D map of the explored space
Contact inhibition of locomotion and mechanical cross-talk between cell-cell and cell-substrate adhesion determines the pattern of junctional tension in epithelial cell aggregates
We generated a computational approach to analyze the biomechanics of
epithelial cell aggregates, either island or stripes or entire monolayers, that
combines both vertex and contact-inhibition-of-locomotion models to include
both cell-cell and cell-substrate adhesion. Examination of the distribution of
cell protrusions (adhesion to the substrate) in the model predicted high order
profiles of cell organization that agree with those previously seen
experimentally. Cells acquired an asymmetric distribution of basal protrusions,
traction forces and apical aspect ratios that decreased when moving from the
edge to the island center. Our in silico analysis also showed that tension on
cell-cell junctions and apical stress is not homogeneous across the island.
Instead, these parameters are higher at the island center and scales up with
island size, which we confirmed experimentally using laser ablation assays and
immunofluorescence. Without formally being a 3-dimensional model, our approach
has the minimal elements necessary to reproduce the distribution of cellular
forces and mechanical crosstalk as well as distribution of principal stress in
cells within epithelial cell aggregates. By making experimental testable
predictions, our approach would benefit the mechanical analysis of epithelial
tissues, especially when local changes in cell-cell and/or cell-substrate
adhesion drive collective cell behavior.Comment: 39 pages, 8 Figures. Supplementary Information is include
Probing the Soft X-ray Properties and Multi-Wavelength Variability of SN2023ixf and its Progenitor
We present a detailed analysis of nearly two decades of optical/UV and X-ray
data to study the multi-wavelength pre-explosion properties and post-explosion
X-ray properties of nearby SN2023ixf located in M101. We find no evidence of
precursor activity in the optical to UV down to a luminosity of , while X-ray observations covering nearly 18
years prior to explosion show no evidence of luminous precursor X-ray emission
down to an absorbed 0.3 - 10.0 keV X-ray luminosity of erg
s. Extensive Swift observations taken post-explosion did not detect soft
X-ray emission from SN2023ixf within the first 3.3 days after first
light, which suggests a mass-loss rate for the progenitor of
yr or a radius of
cm for the circumstellar material. Our analysis also
suggests that if the progenitor underwent a mass-loss episode, this had to
occur 0.5 - 1.5 years prior to explosion, consistent with previous
estimates. Swift detected soft X-rays from SN2023ixf days after
first light, and it rose to a peak luminosity of erg s
after 10 days and has maintained this luminosity for nearly 50 days post first
light. This peak luminosity is lower than expected, given the evidence that
SN2023ixf is interacting with dense material. However, this might be a natural
consequence of an asymmetric circumstellar medium. X-ray spectra derived from
merging all Swift observations over the first 50 days are best described by a
two-component bremsstrahlung model consisting of a heavily absorbed and hotter
component similar to that found using NuSTAR, and a less-absorbed, cooler
component. We suggest that this soft component arises from cooling of the
forward shock similar to that found in Type IIn SN2010jl.Comment: 27 pages, 13 figure
A measurement of the attenuation of radiation from F-18 by a PET/MR scanner
This is the peer reviewed version of the following article: Wendt, R.E., III, Ai, H.A., Meier, J.G., Lopez, B.P., Fahrenholtz, S.J. and Mawlawi, O.R. (2018), A measurement of the attenuation of radiation from F-18 by a PET/MR scanner. J Appl Clin Med Phys, 19: 336-340. , which has been published in final form at https://doi.org/10.1002/acm2.12479. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.https://openworks.mdanderson.org/mdacc_imgphys_pubs/1004/thumbnail.jp
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