253,705 research outputs found
Run Time Approximation of Non-blocking Service Rates for Streaming Systems
Stream processing is a compute paradigm that promises safe and efficient
parallelism. Modern big-data problems are often well suited for stream
processing's throughput-oriented nature. Realization of efficient stream
processing requires monitoring and optimization of multiple communications
links. Most techniques to optimize these links use queueing network models or
network flow models, which require some idea of the actual execution rate of
each independent compute kernel within the system. What we want to know is how
fast can each kernel process data independent of other communicating kernels.
This is known as the "service rate" of the kernel within the queueing
literature. Current approaches to divining service rates are static. Modern
workloads, however, are often dynamic. Shared cloud systems also present
applications with highly dynamic execution environments (multiple users,
hardware migration, etc.). It is therefore desirable to continuously re-tune an
application during run time (online) in response to changing conditions. Our
approach enables online service rate monitoring under most conditions,
obviating the need for reliance on steady state predictions for what are
probably non-steady state phenomena. First, some of the difficulties associated
with online service rate determination are examined. Second, the algorithm to
approximate the online non-blocking service rate is described. Lastly, the
algorithm is implemented within the open source RaftLib framework for
validation using a simple microbenchmark as well as two full streaming
applications.Comment: technical repor
Cytoskeletal dynamics of Cytotoxic T cells during migration in the tumour microenvironment
Typically, migrating T cells display an elongated polarized shape with a very dynamic leading edge and a uropod in the rear. This ‘amoeboid’ movement guarantees a fast migration driven by the formation of polarized protrusions at the front. The actomyosin cytoskeleton is responsible for the generation of the forces that are involved in this process. This thesis aims to determine what is the effect of T cell migration when different components of the actomyosin cortex were inhibited using a pharmacological approach. We found that the inhibition of each component of the actomyosin cortex, T cells display different conformation of the actin filaments and produce different type of protrusion. Furthermore, T cell migration is an important feature for the killing and clearance of canner cells. It has been reported that T cells can migrate efficiently in any kind of tissue whilst scanning for cognate antigen. On the other hand, it is known that the tumor microenvironment secretes immunosuppressive cytokines such as TGF-β impairing the antitumor activity of T cells. Therefore, we aim to determine how TGF-β affects the migration behavior of T cells and its consequences in the scanning strategy to search their cognate antigen
Adaptive Network Dynamics and Evolution of Leadership in Collective Migration
The evolution of leadership in migratory populations depends not only on
costs and benefits of leadership investments but also on the opportunities for
individuals to rely on cues from others through social interactions. We derive
an analytically tractable adaptive dynamic network model of collective
migration with fast timescale migration dynamics and slow timescale adaptive
dynamics of individual leadership investment and social interaction. For large
populations, our analysis of bifurcations with respect to investment cost
explains the observed hysteretic effect associated with recovery of migration
in fragmented environments. Further, we show a minimum connectivity threshold
above which there is evolutionary branching into leader and follower
populations. For small populations, we show how the topology of the underlying
social interaction network influences the emergence and location of leaders in
the adaptive system. Our model and analysis can describe other adaptive network
dynamics involving collective tracking or collective learning of a noisy,
unknown signal, and likewise can inform the design of robotic networks where
agents use decentralized strategies that balance direct environmental
measurements with agent interactions.Comment: Submitted to Physica D: Nonlinear Phenomen
Cytoskeletal dynamics of Cytotoxic T cells during migration in the tumour microenvironment
Typically, migrating T cells display an elongated polarized shape with a very dynamic leading edge and a uropod in the rear. This ‘amoeboid’ movement guarantees a fast migration driven by the formation of polarized protrusions at the front. The actomyosin cytoskeleton is responsible for the generation of the forces that are involved in this process. This thesis aims to determine what is the effect of T cell migration when different components of the actomyosin cortex were inhibited using a pharmacological approach. We found that the inhibition of each component of the actomyosin cortex, T cells display different conformation of the actin filaments and produce different type of protrusion. Furthermore, T cell migration is an important feature for the killing and clearance of canner cells. It has been reported that T cells can migrate efficiently in any kind of tissue whilst scanning for cognate antigen. On the other hand, it is known that the tumor microenvironment secretes immunosuppressive cytokines such as TGF-β impairing the antitumor activity of T cells. Therefore, we aim to determine how TGF-β affects the migration behavior of T cells and its consequences in the scanning strategy to search their cognate antigen
A Fast and Efficient Incremental Approach toward Dynamic Community Detection
Community detection is a discovery tool used by network scientists to analyze
the structure of real-world networks. It seeks to identify natural divisions
that may exist in the input networks that partition the vertices into coherent
modules (or communities). While this problem space is rich with efficient
algorithms and software, most of this literature caters to the static use-case
where the underlying network does not change. However, many emerging real-world
use-cases give rise to a need to incorporate dynamic graphs as inputs.
In this paper, we present a fast and efficient incremental approach toward
dynamic community detection. The key contribution is a generic technique called
, which examines the most recent batch of changes made to an
input graph and selects a subset of vertices to reevaluate for potential
community (re)assignment. This technique can be incorporated into any of the
community detection methods that use modularity as its objective function for
clustering. For demonstration purposes, we incorporated the technique into two
well-known community detection tools. Our experiments demonstrate that our new
incremental approach is able to generate performance speedups without
compromising on the output quality (despite its heuristic nature). For
instance, on a real-world network with 63M temporal edges (over 12 time steps),
our approach was able to complete in 1056 seconds, yielding a 3x speedup over a
baseline implementation. In addition to demonstrating the performance benefits,
we also show how to use our approach to delineate appropriate intervals of
temporal resolutions at which to analyze an input network
Seismic modeling using the frozen Gaussian approximation
We adopt the frozen Gaussian approximation (FGA) for modeling seismic waves.
The method belongs to the category of ray-based beam methods. It decomposes
seismic wavefield into a set of Gaussian functions and propagates these
Gaussian functions along appropriate ray paths. As opposed to the classic
Gaussian-beam method, FGA keeps the Gaussians frozen (at a fixed width) during
the propagation process and adjusts their amplitudes to produce an accurate
approximation after summation. We perform the initial decomposition of seismic
data using a fast version of the Fourier-Bros-Iagolnitzer (FBI) transform and
propagate the frozen Gaussian beams numerically using ray tracing. A test using
a smoothed Marmousi model confirms the validity of FGA for accurate modeling of
seismic wavefields.Comment: 5 pages, 8 figure
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