184 research outputs found
Fast and accurate methods of independent component analysis: A survey
summary:This paper presents a survey of recent successful algorithms for blind separation of determined instantaneous linear mixtures of independent sources such as natural speech or biomedical signals. These algorithms rely either on non-Gaussianity, nonstationarity, spectral diversity, or on a combination of them. Performance of the algorithms will be demonstrated on separation of a linear instantaneous mixture of audio signals (music, speech) and on artifact removal in electroencephalogram (EEG)
Cram\'er-Rao Bounds for Complex-Valued Independent Component Extraction: Determined and Piecewise Determined Mixing Models
This paper presents Cram\'er-Rao Lower Bound (CRLB) for the complex-valued
Blind Source Extraction (BSE) problem based on the assumption that the target
signal is independent of the other signals. Two instantaneous mixing models are
considered. First, we consider the standard determined mixing model used in
Independent Component Analysis (ICA) where the mixing matrix is square and
non-singular and the number of the latent sources is the same as that of the
observed signals. The CRLB for Independent Component Extraction (ICE) where the
mixing matrix is re-parameterized in order to extract only one independent
target source is computed. The target source is assumed to be non-Gaussian or
non-circular Gaussian while the other signals (background) are circular
Gaussian or non-Gaussian. The results confirm some previous observations known
for the real domain and bring new results for the complex domain. Also, the
CRLB for ICE is shown to coincide with that for ICA when the non-Gaussianity of
background is taken into account. %unless the assumed sources' distributions
are misspecified. Second, we extend the CRLB analysis to piecewise determined
mixing models. Here, the observed signals are assumed to obey the determined
mixing model within short blocks where the mixing matrices can be varying from
block to block. However, either the mixing vector or the separating vector
corresponding to the target source is assumed to be constant across the blocks.
The CRLBs for the parameters of these models bring new performance bounds for
the BSE problem.Comment: 25 pages, 8 figure
The expression of epidermal growth factor and transforming growth factor-α mRNA in the small intestine of suckling rats: organ culture study
AbstractEpidermal growth factor (EGF) and transforming growth factor-α (TGF-α) are associated with regulation of various gastrointestinal functions. In order to better understand their role in developing small intestine EGF, TGF-α and EGF-R steady-state mRNA levels and transcript stability were determined. Reverse transcription (RT) competitive-polymerase chain reaction (PCR) revealed that intestinal TGF-α mRNA levels were 10-fold higher in comparison with EGF mRNA. The primary intestinal culture technique was used to evaluate mRNA stability. The stability of TGF-α mRNA was remarkably lower than the stability of EGF mRNA. High levels of TGF-α mRNA accompanied by high degradation rate of this mRNA suggested a rapid turnover of intestinal TGF-α mRNA
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