Evaluation of FFT-Based and Moder Parametrc Methods for the Spectral Analysis of Bioprosthetic Valve Sounds

The objective of this paper is to compare the performance of conventional FFT-based (basic periodogram and Welch's method) and modern parametric (all-pole and pole-zero modeling) methods in estimating the spectral distribution of cardiac bioprosthetic valve sounds, and for the extraction of the two most dominant frequency peaks (DFP). These methods were tested for stability by adding random noise and truncating the bioprosthetic valve closing sounds, and for reproducibility by measuring the variance of the spectra obtained from three consecutive recordings of each patient. Results from a group of 11 patients show that the basic periodogram and Steiglitz-McBride's method with maximum entropy (pole-zero modeling) provide the most consistent (minimal variance) estimates of the DFP's of the closing sounds. However, for estimating spectral distributions, the most stable methods appear to be the basic periodogram and Steiglitz-McBride's method with extrapolation to zero. The basic periodogram appears to be the best compromise to estimate both the spectral distribution and the DFP's of the bioprosthetic closing sounds.     

Mécanisme de l’évolution des champs électromagnétiques dans un simulateur de grandes dimensions. Projet d’un simulateur semi-rhombique

The purpose of this paper is to evaluate theoretically and experimentally the transient electric field in anemp simulator. Using a time domain analysis, the mechanism of the field deformation can be analysed and consequently modifications can be introduced in the conception of new simulators (for example: rhombic simulator).     

Modélisation de l’impédance de transfert des câbles coaxiaux à blindages multiples

The shielding effectiveness of multishielded coaxial cables is determinated through the concept of the equivalent transfer impedance. The transfer impedance is computed from the main parameters of the coaxial structure. We describe in this paper the theoretical formulation to evaluate the amplitude of the disturbing voltage at the end of the cable flowed by the disturbing current. This result is used for the computation of the equivalent transfer impedance when the cable is made of various shields for exemple: homogeneous screens or braids. A comparison with the experimental results is also described.     

Quantification et détection

The basic detection problem consists in deciding on an optimal way between two possible hypotheses. This decision is made by comparing to an appropriate threshold the output of a processing system. The purpose of this paper is to study the consequences of a threshold quantization on the detection performance. Using various possible models of quantization we show that it creates in general a degradation of the performance. From this fact we introduce a new detection criterion using the concept of contrast and we show on some examples how this criterion is adapted to quantized detection problems.     

基于在线激光诱导击穿光谱监控高炉流道中铁水组成的传感器研究

本文旨在描述一种比利时冶金研究中心(CRM)研发的用于钢铁生产领域的传感器。这种以激光诱导击穿光谱(LIBS)技术为基础的传感器可以连续测量高炉流道中的化学成分和温度,其目的在于在线评估铁水的化学成分(主要包括铁,碳,硅和锰),以及其温度。这种传感器也可以测量炉渣中氧化钙、氧化镁、二氧化硅、氧化铝和氧化锰的浓度以及铁粒子的存在,这对于安全生产非常重要。这种传感器已用于比利时根特的阿塞洛米塔尔高炉的可行性测试。     

Lipase-catalyzed synthesis of hydrophobically modified dextrans: activity and regioselectivity of lipase from Candida rugosa

Vinyl decanoate-modified dextran macromolecules (DexT40-VD) were synthesized in dimethyl sulfoxide at 50°C using lipase AY from Candida rugosa for catalyzing transesterification between polysaccharide and vinyl fatty esters. The extent of dextran modification (quantified by the molar ratio of attached alkyl tails to sugar repeat units) with native-, pH-adjusted-, 18-crown-6 ether pretreated pH-adjusted-, and stepwise addition of pretreated lipase AY yielded <3%, 49%, 64% and 96% modified dextran respectively. Lipase AY accelerated the transesterification of DexT40 from 2- to 63-fold higher than the non-catalyzed system. This procedure was extended to other acyl donors showing that modification pattern exhibited regioselectivity depending on acyl donor structure. Regioselectivity equaled between 2- and 3-OH with saturated fatty acyl donors. The 2-OH was favored for unsaturated fatty acyl donors, while sterically hindered acyl donors oriented modification toward 3-OH position. DexT40-VD at 96% modification was a water-insoluble polymer forming 150nm diameter nanoparticles in water which can be used as drug carrier systems.     

Improvement of the identification of four heavy metals in environmental samples by using predictive decision tree models coupled with a set of five bioluminescent bacteria

A primary statistical model based on the crossings between the different detection ranges of a set of five bioluminescent bacterial strains was developed to identify and quantify four metals which were at several concentrations in different mixtures: cadmium, arsenic III, mercury, and copper. Four specific decision trees based on the CHAID algorithm (CHi-squared Automatic Interaction Detector type) which compose this model were designed from a database of 576 experiments (192 different mixture conditions). A specific software, 'Metalsoft', helped us choose the best decision tree and a user-friendly way to identify the metal. To validate this innovative approach, 18 environmental samples containing a mixture of these metals were submitted to a bioassay and to standardized chemical methods. The results show on average a high correlation of 98.6% for the qualitative metal identification and 94.2% for the quantification. The results are particularly encouraging, and our model is able to provide semiquantitative information after only 60 min without pretreatments of samples.     

Heat-induced aggregation of whey proteins in the presence of κ-casein or sodium caseinate

Aggregates were formed by heating mixtures of whey protein isolate (WPI) and pure κ-casein or sodium caseinate at pH 7 and 0.1 M NaCl. The aggregates were characterized by static and dynamic light scattering and size exclusion chromatography. After extensive heat-treatment at 80 °C for 24 h, almost all whey proteins and κ-casein formed mixed aggregates, but a large proportion of the sodium caseinate did not aggregate. At a given WPI concentration the size of the aggregates decreased with increasing κ-casein or sodium caseinate concentration, but the overall self-similar structure of the aggregates was the same. The presence of κ-casein or caseinate therefore inhibited growth of the heat-induced whey protein aggregates. The results were discussed relative to the reported chaperone-like activity of casein molecules towards heat aggregation of globular proteins.