4,019 research outputs found
Closing the Economic Security Equity Gap for Mississippi's BlackMales
Creating opportunities for young men and boys of color to reach their full potential helps to advance individual opportunity, family sustainability, community prosperity, and Mississippi's overall economic competitiveness. Early supports, like positive school climates that fulfill students' socio-emotional needs, help build a foundation for young men and boys of color to succeed and establish economic security into adulthood
Telling time with an intrinsically noisy clock
Intracellular transmission of information via chemical and transcriptional
networks is thwarted by a physical limitation: the finite copy number of the
constituent chemical species introduces unavoidable intrinsic noise. Here we
provide a method for solving for the complete probabilistic description of
intrinsically noisy oscillatory driving. We derive and numerically verify a
number of simple scaling laws. Unlike in the case of measuring a static
quantity, response to an oscillatory driving can exhibit a resonant frequency
which maximizes information transmission. Further, we show that the optimal
regulatory design is dependent on the biophysical constraints (i.e., the
allowed copy number and response time). The resulting phase diagram illustrates
under what conditions threshold regulation outperforms linear regulation.Comment: 10 pages, 5 figure
Kinetic Accessibility of Buried DNA Sites in Nucleosomes
Using a theoretical model for spontaneous partial DNA unwrapping from
histones, we study the transient exposure of protein-binding DNA sites within
nucleosomes. We focus on the functional dependence of the rates for site
exposure and reburial on the site position, which is measurable experimentally
and pertinent to gene regulation. We find the dependence to be roughly
described by a random walker model. Close inspection reveals a surprising
physical effect of flexibility-assisted barrier crossing, which we characterize
within a toy model, the "semiflexible Brownian rotor."Comment: final version as published in Phys. Rev. Let
Hydrodynamic induced deformation and orientation of a microscopic elastic filament
We describe simulations of a microscopic elastic filament immersed in a fluid
and subject to a uniform external force. Our method accounts for the
hydrodynamic coupling between the flow generated by the filament and the
friction force it experiences. While models that neglect this coupling predict
a drift in a straight configuration, our findings are very different. Notably,
a force with a component perpendicular to the filament axis induces bending and
perpendicular alignment. Moreover, with increasing force we observe four shape
regimes, ranging from slight distortion to a state of tumbling motion that
lacks a steady state. We also identify the appearance of marginally stable
structures. Both the instability of these shapes and the observed alignment can
be explained by the combined action of induced bending and non-local
hydrodynamic interactions. Most of these effects should be experimentally
relevant for stiff micro-filaments, such as microtubules.Comment: three figures. To appear in Phys Rev Let
Preface "Nonlinear processes in oceanic and atmospheric flows"
Nonlinear phenomena are essential ingredients in many oceanic and atmospheric
processes, and successful understanding of them benefits from multidisciplinary
collaboration between oceanographers, meteorologists, physicists and
mathematicians. The present Special Issue on ``Nonlinear Processes in Oceanic
and Atmospheric Flows'' contains selected contributions from attendants to the
workshop which, in the above spirit, was held in Castro Urdiales, Spain, in
July 2008. Here we summarize the Special Issue contributions, which include
papers on the characterization of ocean transport in the Lagrangian and in the
Eulerian frameworks, generation and variability of jets and waves, interactions
of fluid flow with plankton dynamics or heavy drops, scaling in meteorological
fields, and statistical properties of El Ni\~no Southern Oscillation.Comment: This is the introductory article to a Special Issue on "Nonlinear
Processes in Oceanic and Atmospheric Flows'', published in the journal
Nonlinear Processes in Geophysics, where the different contributions are
summarized. The Special Issue itself is freely available from
http://www.nonlin-processes-geophys.net/special_issue103.htm
Lagrangian descriptors and the assessment of the predictive capacity of oceanic data sets
We use a recently developed Lagrangian transport tool, <i>Lagrangian
descriptors</i>, to compare the transport properties of data distributed by
AVISO and numerical simulations obtained from the HYCOM model in the
Yucatán–Florida current system. Our data correspond to the months from June
through August 2010. Structures obtained from HYCOM are noisier than those
from AVISO; however, both AVISO and HYCOM succeed in identifying Lagrangian
structures that influence the paths of drifters, such as eddies, currents,
lobes, etc. We find evidence in which AVISO gives the positions of important
hyperbolic trajectories in a manner that is inconsistent with the
trajectories of the drifters, while for the same examples HYCOM succeeds to
this end
Designing Computationally Creative Musical Performance Systems
This is work in progress where we outline a design process for a computationally creative musical performance system using the Creative Systems Framework (CSF). The proposed system is intended to produce virtuosic interpretations, and subsequent synthesized renderings of these interpretations with a physical model of a bass guitar, using case-based reasoning and reflection. We introduce our interpretations of virtuosity and musical performance, outline the suitability of case-based reasoning in computationally creative systems and introduce notions of computational creativity and the CSF. We design our system by formalising the components of the CSF and briefly outline a potential implementation. In doing so, we demonstrate how the CSF can be used as a tool to aid in designing computationally creative musical performance systems
Targeted mixing in an array of alternating vortices
Transport and mixing properties of passive particles advected by an array of
vortices are investigated. Starting from the integrable case, it is shown that
a special class of perturbations allows one to preserve separatrices which act
as effective transport barriers, while triggering chaotic advection. In this
setting, mixing within the two dynamical barriers is enhanced while long range
transport is prevented. A numerical analysis of mixing properties depending on
parameter values is performed; regions for which optimal mixing is achieved are
proposed. Robustness of the targeted mixing properties regarding errors in the
applied perturbation are considered, as well as slip/no-slip boundary
conditions for the flow
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