6,986 research outputs found
Vehicle infrastructure cooperative localization using Factor Graphs
Highly assisted and Autonomous Driving is dependent on the accurate localization of both the vehicle and other targets within the environment. With increasing traffic on roads and wider proliferation of low cost sensors, a vehicle-infrastructure cooperative localization scenario can provide improved performance over traditional mono-platform localization. The paper highlights the various challenges in the process and proposes a solution based on Factor Graphs which utilizes the concept of topology of vehicles. A Factor Graph represents probabilistic graphical model as a bipartite graph. It is used to add the inter-vehicle distance as constraints while localizing the vehicle. The proposed solution is easily scalable for many vehicles without increasing the execution complexity. Finally simulation indicates that incorporating the topology information as a state estimate can improve performance over the traditional Kalman Filter approac
Mechanisms of Bacterial Extracellular Electron Exchange.
The biochemical mechanisms by which microbes interact with extracellular soluble metal ions and insoluble redox-active minerals have been the focus of intense research over the last three decades. The process presents two challenges to the microorganism; firstly electrons have to be transported at the cell surface, which in Gram negative bacteria presents an additional problem of electron transfer across the ~ 6 nm of the outer membrane. Secondly the electrons must be transferred to or from the terminal electron acceptors or donors. This review covers the known mechanisms that bacteria use to transport electrons across the cell envelope to external electron donors/acceptors. In Gram negative bacteria electron transfer across the outer membrane involves the use of an outer membrane β-barrel and cytochrome. These can be in the form of a porin-cytochrome protein, such as Cyc2 of Acidothiobacillus ferrioxydans, or a multiprotein porin-cytochrome complex like MtrCAB of Shewanella oneidensis MR-1. For mineral respiring organisms there is the additional challenge of transferring the electrons from the cell to mineral surface. For the strict anaerobe Geobacter sulfurreducens this requires electron transfer through conductive pili to associated cytochrome OmcS that directly reduces Fe(III)oxides, while the facultative anaerobe S. oneidensis MR-1 accomplishes mineral reduction through direct membrane contact, contact through filamentous extentions and soluble flavin shuttles, all of which require the outer membrane cytochromes MtrC and OmcA in addition to secreted flavin
Modelling coordination in biological systems
We present an application of the Reo coordination paradigm to provide a compositional formal model for describing and reasoning about the behaviour of biological systems, such as regulatory gene networks. Reo governs the interaction and flow of data between components by allowing the construction of connector circuits which have a precise formal semantics. When applied to systems biology, the result is a graphical model, which is comprehensible, mathematically precise, and flexibl
Majorana fermion exchange in quasi-one-dimensional networks
Heterostructures of spin-orbit coupled materials with s-wave superconductors
are thought to be capable of supporting zero-energy Majorana bound states. Such
excitations are known to obey non-Abelian statistics in two dimensions, and are
thus relevant to topological quantum computation (TQC). In a one-dimensional
system, Majorana states are localized to phase boundaries. In order to bypass
the constraints of one-dimension, a wire network may be created, allowing the
exchange of Majoranas by way of junctions in the network. Alicea et al. have
proposed such a network as a platform for TQC, showing that the Majorana bound
states obey non-Abelian exchange statistics even in quasi-one-dimensional
systems. Here we show that the particular realization of non- Abelian
statistics produced in a Majorana wire network is highly dependent on the local
properties of individual wire junctions. For a simply connected network, the
possible realizations can be characterized by the chirality of individual
junctions. There is in general no requirement for junction chiralities to
remain consistent across a wire network. We show how the chiralities of
different junctions may be compared experimentally and discuss the implications
for TQC in Majorana wire networks.Comment: 8 pages, 4 figures, some additional discussion. Updated version for
journal submissio
Deconfined Fermions but Confined Coherence?
The cuprate superconductors and certain organic conductors exhibit transport
which is qualitatively anisotropic, yet at the same time other properties of
these materials strongly suggest the existence of a Fermi surface and low
energy excitations with substantial free electron character. The former of
these features is very difficult to account for if the material possesses three
dimensional coherence, while the latter is inconsistent with a description
based on a two dimensional fixed point. We therefore present a new proposal for
these materials in which they are categorized by a fixed point at which
transport in one direction is not renormalization group irrelevant, but is
intrinsically incoherent, i.e. the incoherence is present in a pure system, at
zero temperature. The defining property of such a state is that single electron
coherence is confined to lower dimensional subspaces (planes or chains) so that
it is impossible to observe interference effects between histories which
involve electrons moving between these subspaces.Comment: 31 pages, REVTEX, 3 eps figures, epsf.tex macr
Decoupled execution of synchronous coordination models via behavioural automata
Synchronous coordination systems allow the exchange of data by logically
indivisible actions involving all coordinated entities. This paper introduces
behavioural automata, a logically synchronous coordination model based on the
Reo coordination language, which focuses on relevant aspects for the
concurrent evolution of these systems. We show how our automata model encodes
the Reo and Linda coordination models and how it introduces an explicit
predicate that captures the concurrent evolution, distinguishing local from
global actions, and lifting the need of most synchronous models to involve all
entities at each coordination step, paving the way to more scalable
implementations
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