Watermark-Driven Acoustic Echo Cancellation

International audienceThe performance of adaptive acoustic echo cancelers (AEC) is sensitive to the non-stationarity and correlation of speech signals. In this article, we explore a new approach based on an adaptive AEC driven by data hidden in speech, to enhance the AEC robustness. We propose a two-stage AEC, where the first stage is a classical NLMS-based AEC driven by the far-end speech. In the signal, we embed-in an extended conception of data hiding-an imperceptible white and stationary signal, i.e. a watermark. The goal of the second stage AEC is to identify the misalignment of the first stage. It is driven by the watermark solely, and takes advantage of its appropriate properties (stationary and white) to improve the robustness of the two-stage AEC to the non-stationarity and correlation of speech, and thus reduce the overall system misadjustment. We test two kinds of implementations: in the first implementation, referred to as A-WdAEC (Adaptive Watermark driven AEC), the watermark is a white stationary Gaussian noise. Driven by this signal, the second stage converges faster than the classical AEC and provides better performance in steady state. In the second implementation, referred to as MLS-WdAEC, the watermark is built from maximum length sequences (MLS). Thus, the second stage performs a block identification of the first stage misalignment, given by the circular correlation watermark/pre-processed version of the first stage residual echo. The advantage of this implementation lies in its robustness against noise and under-modeling. Simulation results show the relevance of the "watermark-driven AEC" approach, compared to the classical "error driven AEC"

Probing the role of helix α1 in the acid-tolerance and thermal stability of the Streptomyces sp. SK Glucose Isomerase by site-directed mutagenesis

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Two new gene clusters involved in the degradation of plant cell wall from the fecal microbiota of Tunisian dromedary

Dromedaries are capable of digesting plant cell wall with high content of lignocellulose of poor digestibility. Consequently, their intestinal microbiota can be a source of novel carbohydrate-active enzymes (CAZymes). To the best of our knowledge, no data are available describing the biochemical analysis of enzymes in dromedary intestinal microbiota.To investigate new hydrolytic enzymes from the dromedary gut, a fosmid library was constructed using metagenomic DNA from feces of non-domestic adult dromedary camels living in the Tunisian desert. High-throughput functional screening of 13756 clones resulted in 47 hit clones active on a panel of various chromogenic and non-chromogenic glycan substrates. Two of them, harboring multiple activities, were retained for further analysis. Clone 26H3 displayed activity on AZO-CM-cellulose, AZCL Carob galactomannan and Tween 20, while clone 36A23 was active on AZCL carob galactomannan and AZCL barley β-glucan. The functional annotation of their sequences highlighted original metagenomic loci originating from bacteria of the Bacteroidetes/Chlorobi group, involved in the metabolization of mannosides and β-glucans thanks to a complete battery of endoand exo-acting glycoside hydrolases, esterases, phosphorylases and transporters

The endocrine-disrupting effect and other physiological responses of municipal effluent on the clam Ruditapes decussatus

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Characterization of glucansucrase and dextran from Weissella sp TN610 with potential as safe food additives

Pear-derived Weissella sp. TN610 produced extracellular glycosyltransferase activity responsible for the synthesis of soluble exopolysaccharide from sucrose. Acid and dextranase-catalyzed hydrolysis revealed that the synthesized polymer was a glucan. According to H-1 and C-13 NMR analysis, the glucan produced by TN610 was a linear dextran made of 96% alpha-(1 -> 6) and 4% alpha-(1 -> 3) linkages. Zymogram analysis confirmed the presence of a unique glucansucrase of approximately 180 kDa in the cell-free supernatant from TN610. The crude enzyme, optimally active at 37 degrees C and pH 5, has promising potential for application as a food additive since it catalyzes dextran synthesis in sucrose-supplemented milk, allowing its solidification. A 4257-bp product corresponding to the mature glucansucrase gene was amplified by PCR from TN610. It encoded a polypeptide of 1418 residues having a calculated molecular mass of 156.089 kDa and exhibiting 96% and 95% identity with glucansucrases from Lactobacillus fermentum Kg3 and Weissella cibaria CMU, respectively. (C) 2012 Elsevier B.V. All rights reserved

Positive clones obtained by high-throughput screening.

<p>Positive clones obtained by high-throughput screening.</p

Comparison of the sequences of 26H3 ORFS with uncharacterized and characterized proteins available in the CAZy and NCBI databases.

<p>Comparison of the sequences of 26H3 ORFS with uncharacterized and characterized proteins available in the CAZy and NCBI databases.</p

Metagenomic polysaccharide utilization loci showing organization of genes involved in the degradation and transport of plant cell wall polysaccharides in 26H3 and 36A23 clusters.

<p>Metagenomic polysaccharide utilization loci showing organization of genes involved in the degradation and transport of plant cell wall polysaccharides in 26H3 and 36A23 clusters.</p

Predicted ORFs present on clone 36A23.

<p>Predicted ORFs present on clone 36A23.</p

Activities detected in the cytoplasmic extracts of clones 26H3 and 36A23.

<p>Activities detected in the cytoplasmic extracts of clones 26H3 and 36A23.</p