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Common Synaptic Input to the Human Hypoglossal Motor Nucleus

Laine, Christopher M.; Bailey, E. Fiona
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
15.87%
The tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼5 Hz. Coherence at frequencies up to ∼10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together...

Modelling mechanisms of social network maintenance in hunter-gatherers

Pearce, Eiluned
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/10/2014 EN
Relevância na Pesquisa
25.85%
Due to decreasing resource densities, higher latitude hunter-gatherers need to maintain their social networks over greater geographic distances than their equatorial counterparts. This suggests that as latitude increases, the frequency of face-to-face interaction decreases for ‘weak tie’ relationships in the outer mating pool (~500-strong) and tribal (~1500-strong) layers of a hunter-gatherer social network. A key question, then, is how a hunter-gatherer tribe sustains coherence as a single identifiable unit given that members are distributed across a large geographic area. The first step in answering this question is to establish whether the expectation that network maintenance raises a challenge for hunter-gatherers is correct, or whether sustaining inter-group contact is in fact trivial. Here I present a null model that represents mobile groups as randomly and independently moving gas particles. The aim of this model is to examine whether face-to-face contact can be maintained with every member of an individual’s tribe at all latitudes even under the baseline assumption of random movement. Contrary to baseline expectations, the number of encounters between groups predicted by the gas model cannot support tribal cohesion and is significantly negatively associated with absolute latitude. In addition...

Design principles of mammalian signaling networks : emergent properties at modular and global scales

Locasale, Jason W
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 249 leaves
ENG
Relevância na Pesquisa
15.76%
This thesis utilizes modeling approaches rooted in statistical physics and physical chemistry to investigate several aspects of cellular signal transduction at both the modular and global levels. Design principles of biological networks and cell signaling processes pertinent to disease progression emerge from these studies. It is my hope that knowledge of these principles may provide new mechanistic insights and conceptual frameworks for thinking about therapeutic intervention into diseases such as cancer and diabetes that arise from aberrant signaling. Areas of interest have emphasized the role of scaffold proteins in protein kinase cascades, modeling relevant biophysical processes related to T cell activation, design principles of signal transduction focusing on multisite phosphorylation, quantifying the notion of signal duration and the time scale dependence of signal detection, and entropy based models of network architecture inferred from proteomics data. These problems are detailed below. The assembly of multiple signaling proteins into a complex by a scaffold protein guides many cellular decisions. Despite recent advances, the overarching principles that govern scaffold function are not well understood. We carried out a computational study using kinetic Monte Carlo simulations to understand how spatial localization of kinases on a scaffold may regulate signaling under different physiological condition. Our studies identify regulatory properties of scaffold proteins that allow them to both amplify and attenuate incoming signals in different biological contexts. In a further...

Integrating Remote Invocation and Distributed Shared State

Tang, Chunqiang ; Chen, DeQing ; Dwarkadas, Sandhya ; Scott, Michael L. (1959 - )
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
ENG
Relevância na Pesquisa
26.12%
Most distributed applications require, at least conceptually, some sort of shared state: information that is non-static but mostly read, and needed at more than one site. At the same time, RPC-based systems such as Sun RPC, Java RMI, CORBA, and .NET have become the de facto standards by which distributed applications communicate. As a result, shared state tends to be implemented either through the redundant transmission of deep-copy RPC parameters or through ad-hoc, application-specific caching and coherence protocols. The former option can waste large amounts of bandwidth; the latter significantly complicates program design and maintenance. To overcome these problems, we propose a distributed middleware system that works seamlessly with RPC-based systems, providing them with a global, persistent store that can be accessed using ordinary reads and writes. In an RPC-based program, shared state serves to (1) support genuine reference parameters in RPC calls, eliminating the need to pass large structures repeatedly by value, or to recursively expand pointer-rich data structures using deep-copy parameter modes; (2) eliminate invocations devoted to maintaining the coherence and consistency of cached data; (3) reduce the number of trivial invocations used simply to put or get data. Relaxed coherence models and aggressive protocol optimizations reduce the bandwidth required to maintain shared state. Integrated support for transactions allows a chain of RPC calls to update that state atomically. We focus in this paper on the implementation challenges involved in combining RPC with shared state...

Bistatic synthetic aperture radar data processing and analysis.

Goh, Alvin Soonlien
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
15.76%
Synthetic Aperture Radar (SAR) operation in a bistatic configuration offers various advantages over its now well-established monostatic counterpart but also poses various challenges, among which are the inversion of the raw bistatic SAR data into imagery, the maintenance of time and phase synchronisation between the separated transmitter and receiver, the application of interferometric techniques to bistatic data, and the polarimetric calibration of field-based bistatic systems in constant motion (particularly those with airborne/spaceborne components). As part of a research programme into the potential benefits and challenges of bistatic SAR, the Ingara fully polarimetric X-band airborne imaging radar system, developed and operated by the Australian Defence Science and Technology Organisation, was upgraded to conduct experimental SAR data collections in a bistatic geometry. Experimental trials of the new bistatic SAR system were conducted in 2007 and 2008 in which the existing airborne radar was operated in a fine-resolution (600 MHz bandwidth) circular spotlight-SAR mode, in conjunction with a newly developed fully polarimetric stationary ground-based bistatic receiver. These trials produced a set of fully polarimetric simultaneously collected monostatic and bistatic SAR data...

Belief Revision in Multi-Agent Systems

Malheiro, Benedita; Jennings, Nicholas; Oliveira, Eugénio
Fonte: Wiley Publicador: Wiley
Tipo: Conferência ou Objeto de Conferência
Publicado em //1994 ENG
Relevância na Pesquisa
46.05%
The ability to respond sensibly to changing and conflicting beliefs is an integral part of intelligent agency. To this end, we outline the design and implementation of a Distributed Assumption-based Truth Maintenance System (DATMS) appropriate for controlling cooperative problem solving in a dynamic real world multi-agent community. Our DATMS works on the principle of local coherence which means that different agents can have different perspectives on the same fact provided that these stances are appropriately justified. The belief revision algorithm is presented, the meta-level code needed to ensure that all system-wide queries can be uniquely answered is described, and the DATMS’ implementation in a general purpose multi-agent shell is discussed.

Improving Assumption based Distributed Belief Revision

Malheiro, Benedita; Oliveira, Eugénio
Fonte: IOS Press Publicador: IOS Press
Tipo: Conferência ou Objeto de Conferência
Publicado em //1995 ENG
Relevância na Pesquisa
56.03%
Belief revision is a critical issue in real world DAI applications. A Multi-Agent System not only has to cope with the intrinsic incompleteness and the constant change of the available knowledge (as in the case of its stand alone counterparts), but also has to deal with possible conflicts between the agents’ perspectives. Each semi-autonomous agent, designed as a combination of a problem solver – assumption based truth maintenance system (ATMS), was enriched with improved capabilities: a distributed context management facility allowing the user to dynamically focus on the more pertinent contexts, and a distributed belief revision algorithm with two levels of consistency. This work contributions include: (i) a concise representation of the shared external facts; (ii) a simple and innovative methodology to achieve distributed context management; and (iii) a reduced inter-agent data exchange format. The different levels of consistency adopted were based on the relevance of the data under consideration: higher relevance data (detected inconsistencies) was granted global consistency while less relevant data (system facts) was assigned local consistency. These abilities are fully supported by the ATMS standard functionalities.

Distributed Belief Revision and Environmental Decision Support

Malheiro, Benedita; Oliveira, Eugénio
Fonte: Limusa Publicador: Limusa
Tipo: Conferência ou Objeto de Conferência
Publicado em //1995 ENG
Relevância na Pesquisa
55.92%
This article discusses the development of an Intelligent Distributed Environmental Decision Support System, built upon the association of a Multi-agent Belief Revision System with a Geographical Information System (GIS). The inherent multidisciplinary features of the involved expertises in the field of environmental management, the need to define clear policies that allow the synthesis of divergent perspectives, its systematic application, and the reduction of the costs and time that result from this integration, are the main reasons that motivate the proposal of this project. This paper is organised in two parts: in the first part we present and discuss the developed - Distributed Belief Revision Test-bed - DiBeRT; in the second part we analyse its application to the environmental decision support domain, with special emphasis on the interface with a GIS.

Distributed Belief Revision and Environmental Decision Support

Malheiro, Benedita; Oliveira, Eugénio
Fonte: Instituto Politécnico do Porto Publicador: Instituto Politécnico do Porto
Tipo: Conferência ou Objeto de Conferência
Publicado em //1996 N/A
Relevância na Pesquisa
55.89%
This article discusses the development of an Intelligent Distributed Environmental Decision Support System, built upon the association of a Multi-agent Belief Revision System with a Geographical Information System (GIS). The inherent multidisciplinary features of the involved expertises in the field of environmental management, the need to define clear policies that allow the synthesis of divergent perspectives, its systematic application, and the reduction of the costs and time that result from this integration, are the main reasons that motivate the proposal of this project. This paper is organised in two parts: in the first part we present and discuss the developed ; in the second part we analyse its application to the environmental decision support domain, with special emphasis on the interface with a GIS.

Design and Evaluation of Mechanisms for a Multicomputer Object Store

Weaver, Lex
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/04/2000
Relevância na Pesquisa
35.94%
Multicomputers have traditionally been viewed as powerful compute engines. It is from this perspective that they have been applied to various problems in order to achieve significant performance gains. There are many applications for which this compute intensive approach is only a partial solution. CAD, virtual reality, simulation, document management and analysis all require timely access to large amounts of data. This thesis investigates the use of the object store paradigm to harness the large distributed memories found on multicomputers. The design, implementation, and evaluation of a distributed object server on the Fujitsu AP1000 is described. The performance of the distributed object server under example applications, mainly physical simulation problems, is used to evaluate solutions to the problems of client space recovery, object migration, and coherence maintenance. The distributed object server follows the client-server model, allows object replication, and uses binary semaphores as a concurrency control measure. Instrumentation of the server under these applications supports several conclusions: client space recovery should be dynamically controlled by the application, predictively prefetching object replicas yields benefits in restricted circumstances...