Density Estimation on the Binary Hypercube using Transformed Fourier-Walsh Diagonalizations

This article focuses on estimating distribution elements over a high-dimensional binary hypercube from multivariate binary data. A popular approach to this problem, optimizing Walsh basis coefficients, is made more interpretable by an alternative representation as a "Fourier-Walsh" diagonalization. Allowing monotonic transformations of the resulting matrix elements yields a versatile binary density estimator: the main contribution of this article. It is shown that the Aitchison and Aitken kernel emerges from a constrained exponential form of this estimator, and that relaxing these constraints yields a flexible variable-weighted version of the kernel that retains positive-definiteness. Estimators within this unifying framework mix together well and span over extremes of the speed-flexibility trade-off, allowing them to serve a wide range of statistical inference and learning problems.Comment: 9 pages, 1 tabl

Algebraic lattices achieve the capacity of the ergodic fading channel

In this work we show that algebraic lattices con- structed from error-correcting codes achieve the ergodic capacity of the fading channel. The main ingredients for our construction are a generalized version of the Minkowski-Hlawka theorem and shaping techniques based on the lattice Gaussian distribution. The structure of the ring of integers in a number field plays an important role in the proposed construction. In the case of independent and identically distributed fadings, the lattices considered exhibit full diversity and an exponential decay of the probability of error with respect to the blocklength

Algebraic lattice Codes achieve the capacity of the compound block-fading channel

We propose a lattice coding scheme that achieves the capacity of the compound block-fading channel. Our lattice construction exploits the multiplicative structure of number fields and their group of units to absorb ill-conditioned channel realizations. To shape the constellation, a discrete Gaussian distribution over the lattice points is applied. A by-product of our results is a refined analysis of the probability of error of the lattice Gaussian distribution in the AWGN channel

A rational use of laboratory tests in the diagnosis and management of hepatitis C virus infection

The prevalence of HCV infection is very diversified according to geographical areas and ranges from 1% in the Northern regions of the world to more than 20% as we move South. Due to the presence of HCVassociated liver diseases and the development of effective treatments, the diagnosis of HCV infection is a growing medical need. Several tests are available, from simple screening to identify the presence of antiHCV antibodies to the more sophisticated quantification of viral load and genotyping. However, these tests are to be used in a logical, consequential and cost-effective manner. This review article will report on the protocol in use in the North-Eastern part of Italy for the screening and diagnosis of HCV infection. The protocol is based on a consensus among several experts and may be the basis for a more rational approach in this rapidly growing field

A Flexible Implementation of a Matrix Laurent Series-Based 16-Point Fast Fourier and Hartley Transforms

This paper describes a flexible architecture for implementing a new fast computation of the discrete Fourier and Hartley transforms, which is based on a matrix Laurent series. The device calculates the transforms based on a single bit selection operator. The hardware structure and synthesis are presented, which handled a 16-point fast transform in 65 nsec, with a Xilinx SPARTAN 3E device.Comment: 4 pages, 4 figures. IEEE VI Southern Programmable Logic Conference 201

The Real and Financial Implications of Corporate Hedging

We study the implications of hedging for corporate financing and investment. We do so using an extensive, hand-collected data set on corporate hedging activities. Hedging can lower the odds of negative realizations, thereby reducing the expected costs of financial distress. In theory, this should ease a firm's access to credit. Using a tax-based instrumental variable approach, we show that hedgers pay lower interest spreads and are less likely to have capital expenditure restrictions in their loan agreements. These favorable financing terms, in turn, allow hedgers to invest more. Our tests characterize two exact channels-cost of borrowing and investment restrictions-through which hedging affects corporate outcomes. The analysis shows that hedging has a first-order effect on firm financing and investment, and provides new insights into how hedging affects corporate value. More broadly, our study contributes novel evidence on the real consequences of financial contracting. © 2011 the American Finance Association.preprin