Brown University

About: Brown University is a education organization based out in Providence, Rhode Island, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 35778 authors who have published 90896 publications receiving 4471489 citations. The organization is also known as: brown.edu & Brown.

Long-Term Depression in Hippocampus

Abstract: Long-term depression (LTD) is a lasting decrease in synaptic effectiveness that follows some types of electrical stimulation in the hippocampus. Two broad types of LTD may be distinguished. Heterosynaptic LTD can occur at synapses that are inactive, normally during high-frequency stimulation of a converging synaptic input. Homosynaptic LTD can occur at synapses that are activated, normally at low frequencies. Here we discuss the mechanisms of LTD and their possible relevance to hippocampal function.

A finite element method for localized failure analysis

Abstract: A method is proposed which aims at enhancing the performance of general classes of elements in problems involving strain localization. The method exploits information concerning the process of localization which is readily available at the element level. A bifurcation analysis is used to determine the geometry of the localized deformation modes. When the onset of localization is detected, suitably defined shape functions are added to the element interpolation which closely reproduce the localized modes. The extra degrees of freedom representing the amplitudes of these modes are eliminated by static condensation. The proposed methodology can be applied to 2-D and 3-D problems involving arbitrary rate-independent material behavior. Numerical examples demonstrate the ability of the method to resolve the geometry of localized failure modes to the highest resolution allowed by the mesh.

Kapitza conductance and heat flow between solids at temperatures from 50 to 300 K.

Abstract: Measurements of the Kapitza conductance ${\mathrm{\ensuremath{\sigma}}}_{\mathit{K}}$ made using a picosecond optical technique at temperatures between 50 and 300 K are presented for interfaces between metals and dielectrics. The Debye temperatures ${\mathit{FTHETA}}_{\mathit{D}}$ of the metals (Pb, Au, Al, and Ti) were in the range from 102 to 426 K, while those of the dielectrics (${\mathrm{BaF}}_{2}$, sapphire, and diamond) varied from 287 to 2200 K. Conductances measured between materials with ${\mathit{FTHETA}}_{\mathit{D}}$ differing by less than about a factor of 5 were found to be in reasonable agreement with calculations based on a lattice dynamical theory. However, for more widely mismatched solids the measured conductances were found to be greatly in excess of the lattice dynamical calculations. In some of these cases the conductances exceeded even the phonon radiation limit, indicating that much of the heat flow between the solids was via an inelastic channel. It was demonstrated experimentally that the inelastic channel does not involve an interaction between the phonons in the dielectric and electrons in the metal. We show that the anomalously large conductance can be understood in terms of a model in which the anharmonicity of the metal plays an important role.

Planning and Control

Abstract: "Planning and Control" explores planning and control by reformulating the two areas in a common control framework, developing the corresponding techniques side-by-side, and identifying opportunities for integrating their ideas and methods. This book is organized around the central roles of prediction, observation, and computation control. The first three chapters deal with predictive models of physical systems based on temporal logic and the differential calculus. Chapter 4 and 5 present some basic concepts in planning and control, including controllability, observability, stability, feedback control, task reduction, conditional plans, and the relationship between goals and preferences. Chapters 6 and 7 consider issues of uncertainty, covering state estimation and the Kalman filter, stochastic dynamic programming, probabilistic modeling, and graph-based decision models. The remaining chapters investigate selected topics in time-critical decision making, adaptive control, and hybrid control architectures. Throughout, the reader is led to consider critical tradeoffs involving the accuracy of prediction, the availability of information from observation, and the costs and benefits of computation in dynamic environments. This book is useful to researchers in artificial intelligence and control theory, and others concerned with the design of complex applications in robotics, automated manufacturing, and time-critical decision support.

Micro Flows: Fundamentals and Simulation

Abstract: Basic Concepts and Technologies * Governing Equations and Slip Models * Shear-Driven and Separated Micro Flows * Pressure-Driven Micro Flows: Slip Flow Regime * Pressure-Driven Flows: Transition and Free- Molecular Regimes * Thermal Effects in Micro Scales * Prototype Applications of Gas Micro Flows * Electrokinetically-Driven Liquid Micro Flows * Numerical Methods for Continuous Simulation * Numerical Methods for Atomistic Simulation