Blind Normalization of Speech From Different Channels

We show how to construct a channel-independent representation of speech that has propagated through a noisy reverberant channel. This is done by blindly rescaling the cepstral time series by a non-linear function, with the form of this scale function being determined by previously encountered cepstra from that channel. The rescaled form of the time series is an invariant property of it in the following sense: it is unaffected if the time series is transformed by any time-independent invertible distortion. Because a linear channel with stationary noise and impulse response transforms cepstra in this way, the new technique can be used to remove the channel dependence of a cepstral time series. In experiments, the method achieved greater channel-independence than cepstral mean normalization, and it was comparable to the combination of cepstral mean normalization and spectral subtraction, despite the fact that no measurements of channel noise or reverberations were required (unlike spectral subtraction).Comment: 25 pages, 7 figure

Simple Model for Attraction between Like-Charged Polyions

We present a simple model for the possible mechanism of appearance of attraction between like charged polyions inside a polyelectrolyte solution. The attraction is found to be short ranged, and exists only in presence of multivalent counterions. The attraction is produced by the correlations in the condensed layers of counterions surrounding each polyion, and appears only if the number of condensed counterions exceeds the threshold, $n > Z/2 \alpha$, where $\alpha$ is the valence of counterions and $Z$ is the polyion charge.Comment: 4 pages, 4 eps figures, also available at http://www.if.ufrgs.br/~arenzon Figure added and a more detailed discussion of conclusion

Vertical Integration and Market Structure

Contractual theories of vertical integration derive firm boundaries as an efficient response to market transaction costs. These theories predict a relationship between underlying features of transactions and observed integration decisions. There has been some progress in testing these predictions, but less progress in quantifying their importance. One difficulty is that empirical applications often must consider firm structure together with industry structure. Research in industrial organization frequently has adopted this perspective, emphasizing how scale and scope economies, and strategic considerations, influence patterns of industry integration. But this research has paid less attention to contractual or organizational details, so that these two major lines of research on vertical integration have proceeded in parallel with only rare intersection. We discuss the value of combining different viewpoints from organizational economics and industrial organization.

The nature of attraction between like charged rods

Comment on the paper of Ha and Liu (Phys. Rev. Lett. {\bf 79}, 1289 (1997)) regarding the nature of attraction between like charged rods. We demostrate that their results do not produce the correct low temperature limit.Comment: Comment to appear in Phys. Rev. Let

The mean-field theory for attraction between like-charged macromolecules

A mean-field theory based on Gibbs-Bogoliubov inequality is constructed to study the interactions between two like-charged polyions. It is shown that contrary to the previously established paradigm, a properly constructed mean-field theory can quantitatively account for the attractive interactions between two like-charged rods.Comment: 5 pages, 2 figures, elsart.sty neede