36876991
Cooperative dynamics coordinated by stochastic noise in a multi-cell system
We investigate a general coupled noisy system with time delays for cooperative behavior in a multi-cell system. The main conclusion is that appropriate noise intensity and coupling are capable of driving the coupled system to synchrony or resonance, which may be exploited by biological organisms actively to facilitate mutual communication. A multi-cell system with a synthetic gene network, which consists of both intracellular and extracellular noise and time delays, is adopted to demonstrate the effect of noise and coupling on collective dynamics.
18780724
Synchronizing a multicellular system by external input: an artificial control strategy
MOTIVATION
Although there are significant advances on elucidating the collective behaviors on biological organisms in recent years, the essential mechanisms by which the collective rhythms arise remain to be fully understood, and further how to synchronize multicellular networks by artificial control strategy has not yet been well explored.


RESULTS
A control strategy is developed to synchronize gene regulatory networks in a multicellular system when spontaneous synchronization cannot be achieved. We first construct an impulsive control system to model the process of periodically injecting coupling substances with constant or random impulsive control amounts into the common extracellular medium, and further study its effects on the dynamics of individual cells. We derive the threshold of synchronization induced by the periodic substance input. Therefore, we can synchronize the multicellular network to a specific collective behavior by changing the frequency and amplitude of the periodic stimuli. Moreover, a two-stage scheme is proposed to facilitate the synchronization in this paper. We show that the presence of the external input may also initiate different dynamics. The multicellular network of coupled repressilators is used to show the effectiveness of the proposed method. The results not only provide a perspective to understand the interactions between external stimuli and intrinsic physiological rhythms, but also may lead to development of realistic artificial control strategy and medical therapy.


AVAILABILITY



CONTACT
aihara@sat.t.u-tokyo.ac.jp.
141843
Noise-induced cooperative behavior in a multicell system
MOTIVATION
All cell components exhibit intracellular noise on account of random births and deaths of individual molecules, and extracellular noise because of environment perturbations. Gene regulation in particular, is an inherently noisy process with transcriptional control, alternative splicing, translation, diffusion and chemical modification reactions, all of which involve stochastic fluctuations. Such stochastic noises may not only affect the dynamics of the entire system but may also be exploited by living organisms to actively facilitate certain functions, such as cooperative behavior and communication.


RESULTS
We have provided a general model and an analytic tool to examine the cooperative behavior of a multicell system with both intracellular and extracellular stochastic fluctuations. A multicell system with a synthetic gene network is adopted to demonstrate the effects of noises and coupling on collective dynamics. These results establish not only a theoretical foundation but also a quantitative basis for understanding essential roles of noises on cooperative dynamics, such as synchronization and communication among cells.
5382814
Network-Embedded Programmable Storage and Its Applications
We consider the utility of two key properties of network-embedded storage: programmability and network-awareness. We describe two extensive applications, whose performance and functionalities are significantly enhanced through innovative combination of the two properties. One is an incremental file-transfer system tailor-made for low-bandwidth conditions. The other is a “customizable” distributed file system that can assume very different personalities in different topological and workload environments. The applications show how both properties are necessary to exploit the full potential of network-embedded storage. We also discuss the requirements of a general infrastructure to support easy and effective access to network-embedded storage, and describe a prototype implementation of such an infrastructure.
1078044
PersonalRAID: Mobile Storage for Distributed and Disconnected Computers
This paper presents the design and implementation of a mobile storage system called a Personal-RAID. PersonalRAID manages a number of disconnected storage devices. At the heart of a Personal-RAID system is a mobile storage device that transparently propagates data to ensure eventual consistency. Using this mobile device, a PersonalRAID provides the abstraction of a single coherent storage name space that is available everywhere, and it ensures reliability by maintaining data redundancy on a number of storage devices. One central aspect of the PersonalRAID design is that the entire storage system consists solely of a collection of storage logs; the log-structured design not only provides an efficient means for update propagation, but also allows efficient direct I/O accesses to the logs without incurring unnecessary log replay delays. The PersonalRAID prototype demonstrates that the system provides the desired transparency and reliability functionalities without imposing any serious performance penalty on a mobile storage user.
1431727
Combining Flexibility and Scalability in a Peer-to-Peer Publish/Subscribe System
The content-based publish/subscribe model has been adopted by many services to deliver data between distributed users based on application-specific semantics. Two key issues in such systems, the semantic expressiveness of content matching and the scalability of the matching mechanism, are often found to be in conflict due to the complexity associated with content matching. In this paper, we present a novel content-based publish/subscribe architecture based on peer-to-peer matching trees. The system achieves scalability by partitioning the responsibility of event matching to self-organized peers while allowing customizable matching functionalities. Experimental results using a variety of real world datasets demonstrate the scalability and flexibility of the system.
6548761
Cooperative caching: using remote client memory to improve file system performance
Emerging high-speed networks will allow machines to access remote data nearly as quickly as they can access local data. This trend motivates the use of cooperative caching: coordinating the file caches of many machines distributed on a LAN to form a more effective overall file cache. In this paper we examine four cooperative caching algorithms using a trace-driven simulation study. These simulations indicate that for the systems studied cooperative caching can halve the number of disk accesses, improving file system read response time by as much as 73%. Based on these simulations we conclude that cooperative caching can significantly improve file system read response time and that relatively simple cooperative caching algorithms are sufficient to realize most of the potential performance gain.
907891
Segank: A Distributed Mobile Storage System
This paper presents a distributed mobile storage system designed for storage elements connected by a network of non-uniform quality. Flexible data placement is crucial, and it leads to challenges for locating data and keeping it consistent. Our system employs a location- and topology-sensitive multicast-like solution for locating data, lazy peer-to-peer propagation of invalidation information for ensuring consistency, and a distributed snapshot mechanism for supporting sharing. The combination of these mechanisms allows a user to make the most of what a non-uniform network has to offer in terms of gaining fast access to fresh data, without incurring the foreground penalty of keeping distributed elements on a weak network consistent.