Double-Talk-Robust Prediction Error Identification Algorithms for Acoustic Echo Cancellation

The performance of an acoustic echo canceller may be severely degraded by the presence of a near-end signal. In such a double-talk situation, the variance of the echo path estimate typically increases, resulting in slow convergence or even divergence of the adaptive filter. This problem is usually tackled by equipping the echo canceller with a double-talk detector that freezes adaptation during near-end activity. Nevertheless, there is a need for more robust adaptive algorithms since the adaptive filter's convergence may be affected considerably in the time interval needed to detect double-talk. Moreover, in some applications, near-end noise may be continuously present and then the use of a double-talk detector becomes futile. Robustness to double-talk may be established by taking into account the near-end signal characteristics, which are, however, unknown and time varying. In this paper, we show how concurrent estimation of the echo path and an autoregressive near-end signal model can be performed using prediction error (PE) identification techniques. We develop a general recursive prediction error (RPE) identification algorithm and compare it to three existing algorithms from adaptive feedback cancellation. The potential benefit of the algorithms in a double-talk situation is illustrated by means of computer simulations. It appears that especially in the stochastic gradient case a huge improvement in convergence behavior can be obtained     

Fumonisin B1 in maize for food production imported in The Netherlands

STATEMENT OF PROBLEM: When compared with waxes and prefabricated components made of dental alloys, processing resins is difficult and often results in a less accurate fit. The exact linear dimension is hard to realize, as the materials required for a dental casting are adjusted to dental waxes, and usually there are no special processing instructions for these resins. PURPOSE: The surface structure of 16 residue-free burning resins was determined to find which could enlarge the range of application for waxes in the dental casting technique. MATERIAL AND METHODS: A total of 480 specimens (30 castings for each of 16 resins) were marked with an individually cut pyramid, which left an impression in the resin. This was distinctly visible in the metal after casting in "the lost form." The surfaces of these 480 specimens were measured in three dimensions with a positioning aid "before casting in resin" and "after casting in metal" by the Perthometer micrometer. All specimens were treated identically by the lost-wax process by using the rotation symmetry of the muffle. The differences in the surface data before casting in resin and after casting in metal characterize the quality of the particular resin. RESULTS: Surface roughness differed between the 16 resins in the range of micrometer. CONCLUSIONS: With the dental casting technique, it is recommended that some resins replace waxes or wax-resin compositions.     

Value of intravascular ultrasound in angiographically underestimated coronary findings: exemplified by 2 case reports]

Ultrastructural alteration of anionic sites (ASs) in the glomerular basement membrane (GBM) was studied in 10 cases of swine mesangial proliferative glomerulonephritis using a cationic ultrastructural tracer, 0.5% polyethyleneimine (M.W. = 1,800). Glomerular ASs were seen as discrete electron-dense particles in the GBM, mesangial matrix and epithelial cell surfaces by electron microscopy. In the lamina rara externa (LRE) of the normal GBM, ASs were distributed regularly in a single layer. In those areas of the LRE that contained electron dense deposits or clusters of spherical microparticles (SMPs), however, a distinct reduction or loss of ASs was observed in all the pigs. Quantitative assessment of ASs in the LRE over 1,000 nm of the GBM revealed a significant reduction in ASs in one case with diffuse global thickening of the GBM as compared with the remaining nine pigs without GBM thickening (P < 0.001, Mann-Whitney's U-test). There were no ASs in the lamina densa (LD) of the normal GBM, but an irregular distribution of ASs was seen within the LD of the pig showing diffuse global thickening of the GBM. These results suggest that a disturbance of the charge-selective barrier in the GBM may be induced by electron-dense deposits or SMPs, in the LRE as well as thickening of the GBM in swine glomerulonephritis.     

Acoustic feedback cancellation for long acoustic paths using a nonstationary source model

While several proactive acoustic feedback (Larsen-effect) cancellation schemes have been presented for speech applications with short acoustic feedback paths as encountered in hearing aids, these schemes fail with the long impulse responses inherent to, for instance, public address systems. We derive a new prediction error method (PEM)-based scheme (referred to as PEM-AFROW) which identifies both the acoustic feedback path and the nonstationary speech source model. A cascade of a short- and a long-term predictor removes the coloring and periodicity in voiced speech segments, which account for the unwanted correlation between the loudspeaker signal and the speech source signal. The predictors calculate row operations which are applied to prewhiten the speech source signal, resulting in a least squares system that is solved recursively by means of normalized least mean square or recursive least squares algorithms. Simulations show that this approach is indeed superior to earlier approaches whenever long acoustic channels are dealt with.     

Semiparametric multivariate density estimation for positive data using copulas

The estimation of density functions for positive multivariate data is discussed. The proposed approach is semiparametric. The estimator combines gamma kernels or local linear kernels, also called boundary kernels, for the estimation of the marginal densities with parametric copulas to model the dependence. This semiparametric approach is robust both to the well-known boundary bias problem and the curse of dimensionality problem. Mean integrated squared error properties, including the rate of convergence, the uniform strong consistency and the asymptotic normality are derived. A simulation study investigates the finite sample performance of the estimator. The proposed estimator performs very well, also for data without boundary bias problems. For bandwidths choice in practice, the univariate least squares cross validation method for the bandwidth of the marginal density estimators is investigated. Applications in the field of finance are provided.     

Antibiotic susceptibility of campylobacter isolates from sewage and poultry abattoir drain water

In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11-18% quinolone resistance for SPB isolates to 17-33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.     

A simple on-chip repetitive sampling setup for the quantification of substrate noise

The quantification of substrate noise is an important issue in mixed-signal designs, where sensitive analog circuits are embedded in a hostile digital environment. In this paper we present an experimental environment to characterize the sensitivity of embedded analog circuits to digitally generated substrate noise. Our measurement technique is based on equivalent-time substrate voltage sampling and uses a simple differential latch comparator without explicit input sample-and-hold. A surprisingly large measurement bandwidth is observed,which is explained from the detailed circuit behavior. On our 0.18-/spl mu/m CMOS test chip,we have demonstrated that our system allows to wave trace pulses as narrow as 200 ps accurately. Additionally, the extraction of precise measurement data from observations that are excessively corrupted by additive noise and timing jitter is addressed. We present simple yet very effective methods to accurately reconstruct pulse waveform features without the use of delicate deconvolution operations.     

Auto‐Tandem Catalysis: Synthesis of Substituted 11H‐Indolo[3,2‐c]quinolines via Palladium‐Catalyzed Intermolecular C?N and Intramolecular C?C Bond Formation

D ‐Ring substituted 11H‐indolo[3,2‐c]quinolines ( 4 ) have been prepared via auto‐tandem consecutive intermolecular Buchwald‐Hartwig reaction and intramolecular palladium‐catalyzed arylation on 4‐chloroquinoline ( 1 ) with N‐unsubstituted 2‐chloroanilines ( 2 ). The reported 11H‐indolo[3,2‐c]quinolines ( 4 ) represent the first examples in which tandem catalysis has been used to construct N‐unsubstituted carbolines.     

Impact of parboiling conditions on Maillard precursors and indicators in long-grain rice cultivars

The effect of steaming conditions (mild, intermediate and severe) during parboiling of five different long-grain rice cultivars (brown rice cultivars Puntal, Cocodrie, XL8 and Jacinto, and a red rice) on rice colour, and Maillard precursors and indicators was investigated. Rice colour increased with severity of parboiling conditions. Redness increased more than yellowness when parboiling brown rice. Parboiling turned red rice black. It changed the levels of glucose, fructose, sucrose, and maltose. Losses of the non-reducing sugar, sucrose were caused by both leaching into the soaking water and enzymic conversion, rather than by thermal degradation during steaming. Concentrations of the reducing sugars, glucose and fructose, in intermediately parboiled rice were higher than those of mildly parboiled rice. After severe parboiling, glucose levels were lower than those of intermediately parboiled rice, while fructose levels were higher. These changes were ascribed to the sum of losses in the Maillard reaction (MR), formations as a result of starch degradation and isomerisation of glucose into fructose. It was clear that the ε-amino group of protein-bound lysine was more affected by parboiling conditions and loss in MRs, than that of free lysine. Low values of the MR indicators furosine and free 5-hydroxymethyl-2-furaldehyde (HMF) in processed brown and red rices were related to mild parboiling, whereas high furosine and low free HMF levels were indicative of rices being subjected to intermediate processing conditions. High furosine and high free HMF contents corresponded to severe hydrothermal treatments. The strong correlation (r = 0.89) between the free HMF levels and the increase in redness of parboiled brown rices suggested that Maillard browning was reflected more in the red than in the yellow colour.     

Campylobacter jejuni non-culturable coccoid cells.

The behaviour of Campylobacter jejuni in the environment is poorly documented. Rapid loss of viability on culture media is reported. This phenomenon is associated with the development of so-called coccoid cells. It has been suggested that these cells can be infective to animals and man. Results obtained with ATP-measurements of coccoid cells and Direct Viable Count (DVC) support this hypothesis. Introduction of coccoid cells into simulated gastric, ileal and colon environments did not result in the presence of culturable cells. Oral administration to laboratory animals and volunteers caused no typical symptoms of campylobacteriosis. Until 30 days after uptake of the cells antibodies against C. jejuni could not be detected in the blood, and the presence of this microorganism in stool samples could not be demonstrated.