21,114 research outputs found

    Our Troubled Health Care System: Why Is It So Hard to Fix? Nineteenth Annual Herbert Lourie Memorial Lecture on Health Policy.

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    This brief draws heavily on Judith Feder, 2004, "Crowd-Out and the Politics of Health Reform," The Journal of Law, Medicine, and Ethids 32(3): 461-464. We all know that affordable health care is now back on the political agenda, and it's about time! Because all of us--families, businesses, and governments--are struggling with the ever-increasing costs of care. Every year about a million people are added to the rolls of the uninsured. In 2006, it was even more, over 2 million. The number of people without health insurance coverage has reached more than 47 million. People *with* insurance are seeing their benefits dwindle and their health care costs consume their wabes. Even people with health insurance find themselves unable to pay their medical bills and going without needed care. The bottom line is that, increasingly, our health insurance system fails to protect us when we get sick.health insurance, uninsurance, cost of medical care

    On the calculation of the minimax-converse of the channel coding problem

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    A minimax-converse has been suggested for the general channel coding problem by Polyanskiy etal. This converse comes in two flavors. The first flavor is generally used for the analysis of the coding problem with non-vanishing error probability and provides an upper bound on the rate given the error probability. The second flavor fixes the rate and provides a lower bound on the error probability. Both converses are given as a min-max optimization problem of an appropriate binary hypothesis testing problem. The properties of the first converse were studies by Polyanskiy and a saddle point was proved. In this paper we study the properties of the second form and prove that it also admits a saddle point. Moreover, an algorithm for the computation of the saddle point, and hence the bound, is developed. In the DMC case, the algorithm runs in a polynomial time.Comment: Extended version of a submission to ISIT 201

    Optimal Feedback Communication via Posterior Matching

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    In this paper we introduce a fundamental principle for optimal communication over general memoryless channels in the presence of noiseless feedback, termed posterior matching. Using this principle, we devise a (simple, sequential) generic feedback transmission scheme suitable for a large class of memoryless channels and input distributions, achieving any rate below the corresponding mutual information. This provides a unified framework for optimal feedback communication in which the Horstein scheme (BSC) and the Schalkwijk-Kailath scheme (AWGN channel) are special cases. Thus, as a corollary, we prove that the Horstein scheme indeed attains the BSC capacity, settling a longstanding conjecture. We further provide closed form expressions for the error probability of the scheme over a range of rates, and derive the achievable rates in a mismatch setting where the scheme is designed according to the wrong channel model. Several illustrative examples of the posterior matching scheme for specific channels are given, and the corresponding error probability expressions are evaluated. The proof techniques employed utilize novel relations between information rates and contraction properties of iterated function systems.Comment: IEEE Transactions on Information Theor

    An Achievable Rate for the MIMO Individual Channel

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    We consider the problem of communicating over a multiple-input multiple-output (MIMO) real valued channel for which no mathematical model is specified, and achievable rates are given as a function of the channel input and output sequences known a-posteriori. This paper extends previous results regarding individual channels by presenting a rate function for the MIMO individual channel, and showing its achievability in a fixed transmission rate communication scenario.Comment: to be presented at ITW201

    Relativistic effects on LEED intensities from Au(111)

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    Comparison of relativistically and nonrelativistically calculated intensity versus energy profiles in low energy electron diffraction (LEED) from the (111) surface of Au (Z = 79) reveals that relativistic corrections are quite significant. They can however, be obtained in very good approximation by quasirelativistic calculations, in which spin-averaged relativistic phase shifts are used as input for the nonrelativistic multiple scattering formalism. Further, relativistic effects on intensities are found to be comparable to differences arising from different approximations to the exchange part of the ion core potential
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