Residual feedback suppression with extended model-based postfilters

When designing closed-loop electro-acoustic systems, which can commonly be found in hearing aids or public address systems, the most challenging task is canceling and/or suppressing the feedback caused by the acoustic coupling of the transducers of such systems. In many applications, feedback cancelation based on adaptive filters is used for this purpose. However, due to computational complexity such a feedback canceler is often limited in the length of the filter’s impulse response. Consequently, a residual feedback, which is still audible and may lead to system instability, remains in most cases. In this work, we present enhancements for model-based postfilters based on a priori knowledge of the feedback path which can be used cooperatively with the adaptive filter-based feedback cancelation system to suppress residual feedback and improve the overall feedback reduction capability. For this, we adapted an existing reverberation model such that our model additionally considers the presence and the performance of the adaptive filter. We tested the effectiveness of our approach by means of both objective and subjective evaluations.

Enhanced Endogenous Amino Acids and Energy Metabolism Level for cAMP Biosynthesis by Arthrobacter sp. CCTCC 2013431 with Citrate as Cosubstrate

Objectives In our previous study, citrate was used as auxiliary energy substance for improving cAMP fermentation performance, however, the regulation mechanism of citrate on improved cAMP contents was not clear. To elucidate the regulation mechanism, cAMP fermentations with/without citrate addition were conducted in a 7 L fermentor using Arthrobacter sp. CCTCC 2013431 and assays on key enzymes activities, energy metabolism level, amino acids contents and peroxidation level were performed. Results With 3 g/L-broth sodium citrate added, cAMP concentration and conversion yield from glucose reached 4.34 g/L and 0.076 g/g which were improved by 30.7% and 29.8%, respectively, when compared with those of control. Citrate changed carbon flux distribution among different routes and more carbon flux was directed into pentose phosphate pathway beneficial to cAMP synthesis. Meanwhile, energy metabolism together with precursor amino acids levels were improved significantly owing to strengthened metabolic intensity of tricarboxylate cycle by exogenous citrate utilization which provided energy and substance basis for cAMP production. Moreover, higher glutamate synthesis and oxidative stress caused by citrate addition consumed excessive NADPH derived from pentose phosphate pathway by which feedback suppression for pentose phosphate pathway was relieved efficiently.Conclusion Citrate promoted cAMP fermentation production by Arthrobacter sp. CCTCC2013431 due to enhanced precursor amino acids, energy metabolism level and relieved feedback suppression for pentose phosphate pathway.

Significance of Crooke's Hyaline Change in Nontumorous Corticotrophs of Patients With Cushing Disease

BackgroundGlucocorticoid excess in Cushing disease (CD) leads to negative feedback suppression, resulting in Crooke's hyaline change (CC) of nontumorous pituitary corticotrophs. We aimed to determine the predictive value of CC of nontumorous corticotrophs in CD.MethodsThe retrospective chart review study included patients with clinical, biochemical, radiologic and outcome data and evaluable histopathology specimens from pituitary surgery for CD. The main outcome was remission of CD, defined by clinical features, biochemical testing, and corticosteroid dependency.ResultsOf 144 CD patients, 60 (50 women, mean age 43.6±14) had clinical follow-up, biochemical data and histopathology specimens that included evaluable nontumorous adenohypophysis. Specimens from 50 patients (83.3%) demonstrated CC in nontumorous corticotrophs, and 10 (16.7%) had no CC (including 3 with corticotroph hyperplasia). One patient with CC was lost to follow-up and one without CC had equivocal outcome results. During a mean (SD) follow-up period of 74.9 months (61.0), recurrent or persistent disease was documented in 18 patients (31.0%), while 40 (69.0%) were in remission. In patients with CC, the remission rate was 73.5% (95% CI, 59.7%-83.7%) (36/49), whereas it was 44.4% (95% CI, 18.9%-73.3%) (4/9) in patients with no CC. The combination of serum cortisol >138 nmol/L within a week of surgery coupled with absence of nontumorous CC greatly improved the prediction of recurrent or persistent disease.ConclusionsCC of nontumorous corticotrophs was observed in 83% of patients with CD, and most patients with CC experienced remission. Absence of CC in nontumorous corticotrophs may serve as a predictor of reduced remission in patients with CD.

Consumer Opinion of Personal Sound Amplification Products: A Preliminary Sentiment Analysis

Purpose The purpose of this study was to preliminarily investigate the sentiments associated with consumer opinions of personal sound amplification products (PSAPs). Method Online reviews of 21 popular PSAPs were collected from the Amazon.com website. The reviews for each product were exported to compile individual product-specific text files. A sentiment mining analysis was completed to aggregate the number of positive and negative comments for each product. In addition, the effect of value for money, available features, perceived benefit, and overall perception of PSAPs was evaluated. A correlational analysis was completed to examine the relationship between different PSAP features and the number of positive and negative comments. Results Mixed-model analysis of variance showed a significantly higher number of positive comments for high- and mid-cost products in terms of overall perception and perceived benefit compared to low-cost products. For feature attribute, high-cost products had significantly higher positive comments compared to mid- and low-cost products. There was a strong correlation between price and positive comments and a moderate correlation between price and negative comments. Also, there was a significant moderate correlation between presence of compression and feedback suppression PSAP features and positive comments. Conclusions Positive sentiments expressed toward PSAPs were found to favor high- and mid-level products. However, there was a considerably high number of negative sentiments reported across all the PSAPs investigated. The noticeable thing is that the negative comments do not change significantly across price ranges. However, the positive comments significantly increase with an increase in product price range. This indicates a possible increase in benefit with high-cost products. However, this claim requires further empirical evidence through controlled studies.