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101
Reduction of the Hodgkin-Huxley Equations to a Single-Variable Threshold Model
- NEURAL COMPUTATION
, 1997
"... It is generally believed that a neuron is a threshold element which fires when some variable u reaches a threshold. Here we pursue the question of whether this picture can be justified and study the four-dimensional neuron model of Hodgkin and Huxley as a concrete example. The model is approximat ..."
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Cited by 87 (25 self)
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It is generally believed that a neuron is a threshold element which fires when some variable u reaches a threshold. Here we pursue the question of whether this picture can be justified and study the four-dimensional neuron model of Hodgkin and Huxley as a concrete example. The model is approximated by a response kernel expansion in terms of a single variable, the membrane voltage. The first-order term is linear in the input and has the typical form of an elementary postsynaptic potential. Higher-order kernels take care of nonlinear interactions between input spikes. In contrast to the standard Volterra expansion the kernels depend on the firing time of the most recent output spike. In particular, a zero-order kernel which describes the shape of the spike and the typical afterpotential is included. Our model neuron fires, if the membrane voltage, given by the truncated response kernel expansion crosses a threshold. The threshold model is tested on a spike train generated by t...
Prevalence of skin cancer in an endemic area of chronic arsenicism
- in Taiwan. J Natl Cancer Inst
, 1968
"... SUMMARY-In a limited area on the southwest coast of Taiwan where artesian well water with a high concentration of arsenic has been used for more than 45 years, a high prevalence of chronic arsenic poisoning has been observed in recent years. The total population of this endemic area, which is define ..."
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Cited by 76 (0 self)
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SUMMARY-In a limited area on the southwest coast of Taiwan where artesian well water with a high concentration of arsenic has been used for more than 45 years, a high prevalence of chronic arsenic poisoning has been observed in recent years. The total population of this endemic area, which is defined by the presence of both patients and contaminated wells, is approximately 100,000. A general survey of 40,421 inhabitants (19,269 males and 21,152 females) of the area was made. The overall prevalence rates for skin cancer, hyperpigmentation, and keratosis were 10.6, 183.5, and 71.0/1000, respectively. The male-to-female ratio was 2.9: 1 for skin cancer and 1.1: 1 for hyperpigmentation and keratosis, respectively. Generally speaking, the prevalence increased steadily with age in all three conditions, though there was a decline in age groups above 69 in females with cancer or hyperpigmentation. The prevalence rate for skin cancer showed an ascending gradient according to the arsenic content of the well water, i.e., the higher the arsenic content, the more patients with skin
Stability and Instability of Fluid Models for Re-Entrant Lines
, 1996
"... Re-entrant lines can be used to model complex manufacturing systems such as wafer fabrication facilities. As the first step to the optimal or near-optimal scheduling of such lines, we investigate their stability. In light of a recent theorem of Dai (1995) which states that a scheduling policy is sta ..."
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Cited by 65 (18 self)
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Re-entrant lines can be used to model complex manufacturing systems such as wafer fabrication facilities. As the first step to the optimal or near-optimal scheduling of such lines, we investigate their stability. In light of a recent theorem of Dai (1995) which states that a scheduling policy is stable if the corresponding fluid model is stable, we study the stability and instability of fluid models. To do this we utilize piecewise linear Lyapunov functions. We establish stability of First-Buffer-First-Served (FBFS) and Last-Buffer-First-Served (LBFS) disciplines in all reentrant lines, and of all work-conserving disciplines in any three buffer re-entrant lines. For the four buffer network of Lu and Kumar we characterize the stability region of the Lu and Kumar policy, and show that it is also the global stability region for this network. We also study stability and instability of Kelly-type networks. In particular, we show that not all work-conserving policies are stable for such netw...
Signaling in plant-microbe interaction
- Science
, 1997
"... Analysis of viral and bacterial pathogenesis has revealed common themes in the ways in which plants and animals respond to pathogenic agents. Pathogenic bacteria use macromolecule delivery systems (types III and IV) to deliver microbial avirulence proteins and transfer DNA-protein complexes directly ..."
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Cited by 54 (1 self)
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Analysis of viral and bacterial pathogenesis has revealed common themes in the ways in which plants and animals respond to pathogenic agents. Pathogenic bacteria use macromolecule delivery systems (types III and IV) to deliver microbial avirulence proteins and transfer DNA-protein complexes directly into plant cells. The molecular events that constitute critical steps of plant-pathogen interactions seem to involve ligand-receptor mechanisms for pathogen recognition and the induction of signal transduction pathways in the plant that lead to defense responses. Unraveling the molecular basis of disease resistance pathways has laid a foundation for the rational design of crop protection strategies. Since the onset of civilization, plant dis-eases have had catastrophic effects on crops and the well-being of human popu-lations. For example, the fungus Phytoph-thora infestans caused the epidemic that triggered the Irish potato famine of the 1840s. Infectious plant diseases continue to cause human suffering and enormous economic losses. An increasing human population and decreasing amounts of land available for agriculture make all ap-proaches to securing the world food supply critical. Protection of crops from disease can substantially improve agricultural pro-duction. Although pesticides have suc-cessfully controlled disease, their contin-ued and increasing use will have harmful effects on our health and the environ-ment. Use of high-yield crop varieties can also improve productivity, but carries a risk—such genetically uniform varieties cultivated over enormous areas are suscep-tible to devastating epidemics. Thoughtful application of the plant’s own defense mechanisms, combined with understand-ing of the complex ecology of real-world disease processes, can lead to more effec-tive protection against plant pathogens. In this review we analyze plant pathogen in-teractions, including microbial strategies for pathogenesis and key elements of host responses (Figs. 1 and 2). We focus on studies using the model plant Arabidopsis thaliana. Symbiotic interactions such as that of legume and Rhizobium are related and have been reviewed elsewhere (1, 2).
P.D.: Landau Hamiltonians with random potentials: localization and the density of states
- Commun. Math. Phys
, 1996
"... We prove the existence of localized states at the edges of the bands for the two-dimensional Landau Hamiltonian with a random potential, of arbitrary disorder, provided that the magnetic field is sufficiently large. The corresponding eigenfunctions decay exponentially with the magnetic field and dis ..."
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Cited by 35 (9 self)
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We prove the existence of localized states at the edges of the bands for the two-dimensional Landau Hamiltonian with a random potential, of arbitrary disorder, provided that the magnetic field is sufficiently large. The corresponding eigenfunctions decay exponentially with the magnetic field and distance. We also prove that the integrated density of states is Lipschitz continuous away from the Landau energies. The proof relies on a Wegner estimate for the finite-area magnetic Hamiltonians with random potentials and exponential decay estimates for the finite-area Green’s functions. The proof of the decay estimates for the Green’s functions uses fundamental results from two-dimensional bond percolation theory. Key-Words: Landau Hamiltonians, random operators, localization. Number of figures: 4
A Conservative Formulation For Plasticity
- Adv. Appl. Math
, 1992
"... . In this paper we propose a fully conservative form for the continuum equations governing rate-dependent and rate-independent plastic flow in metals. The conservation laws are valid for discontinuous as well as smooth solutions. In the ratedependent case, the evolution equations are in divergence f ..."
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Cited by 17 (6 self)
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. In this paper we propose a fully conservative form for the continuum equations governing rate-dependent and rate-independent plastic flow in metals. The conservation laws are valid for discontinuous as well as smooth solutions. In the ratedependent case, the evolution equations are in divergence form, with the plastic strain being passively convected and augmented by source terms. In the rate-independent case, the conservation laws involve a Lagrange multiplier that is determined by a set of constraints; we show that Riemann problems for this system admit scale-invariant solutions. 1. Introduction In a previous paper [24], we formulated the equations for elasticity in the Eulerian picture as conservation laws. The motivation for this work was that the Eulerian framework is useful in numerical computations of large-deformation flows. Furthermore, the most effective numerical methods, such as second-order Godunov schemes and the front tracking method, rely on an understanding of the s...
A real-time service-oriented architecture for industrial automation
- IEEE Transactions on Industrial Informatics
"... Abstract—Industrial automation platforms are experiencing a paradigm shift. New technologies are making their way in the area, including embedded real-time systems, standard local area networks like Ethernet, Wi-Fi and ZigBee, IP-based communica-tion protocols, standard Service Oriented Architecture ..."
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Cited by 13 (2 self)
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Abstract—Industrial automation platforms are experiencing a paradigm shift. New technologies are making their way in the area, including embedded real-time systems, standard local area networks like Ethernet, Wi-Fi and ZigBee, IP-based communica-tion protocols, standard Service Oriented Architectures (SOAs) and Web Services. An automation system will be composed of flexible autonomous components with Plug & Play functionality, self configuration and diagnostics, and autonomic local control that communicate through standard networking technologies. However, the introduction of these new technologies raises im-portant problems that need to be properly solved, one of these being the need to support real-time and quality-of-service (QoS) for real-time applications. This paper describes a SOA enhanced with real-time capabilities for Industrial Automation. The pro-posed architecture allows for negotiation of the QoS requested by clients from web services, and provides temporal encapsulation of individual activities. This way, it is possible to perform an a priori analysis of the temporal behavior of each service, and to avoid unwanted interference among them. After describing the archi-tecture, experimental results gathered on a real implementation of the framework (which leverages a soft real-time scheduler for the Linux kernel) are presented, showing the effectiveness of the proposed solution. The experiments were performed on simple case studies designed in the context of industrial automation applications. Index Terms—Industrial automation, real-time embedded sys-tems, service-oriented architectures (SOAs). I.
Solving Large Nonsymmetric Sparse Linear Systems Using MCSPARSE
- PARALLEL COMPUTING
, 1996
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