The identification of mycobacteria outside biocontainment facilities requires that the organisms first be rendered inactive. Exposure to 70% ethanol (EtOH) either before or after mechanical disruption was evaluated in order to establish a safe, effective, and rapid inactivation protocol that is compatible with identification of Mycobacterium and Nocardia species using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). A combination of 5 min of bead beating in 70% EtOH followed by a 10-min room temperature incubation period was found to be rapidly bactericidal and provided high-quality spectra compared to spectra obtained directly from growth on solid media. The age of the culture, the stability of the refrigerated or frozen lysates, and freeze-thaw cycles did not adversely impact the quality of the spectra or the identification obtained. Different approaches have been developed to hasten the identification of clinically significant mycobacteria compared to traditional biochemical phenotyping. These include DNA probe hybridization-and nucleic acid amplification-based assays with or without sequencing (1-4) and high-performance liquid chromatography (HPLC) to evaluate the mycolic acid composition (1, 2). More recently, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been shown to be a reliable and rapid means for the identification of bacterial species, including mycobacteria through the recognition of specific proteins (5), PCR amplification profiles (6), or protein spectral profiles (7,8). Advanced databases for use with the latter approach are currently being expanded. Regardless of which option is used, it is essential that cultures are rendered nonviable prior to processing outside appropriate biocontainment facilities for obvious safety reasons. Previous reports have identified a variety of ways in which mycobacteria, including Mycobacterium tuberculosis can be successfully inactivated prior to manipulation, including heat treatment (9), exposure to lethal irradiation with or without photosensitizing chemicals (10-12), alcohol exposure (13), or a combination of treatments (14-16). While most were successful, temperatures and/or exposure times varied in order to achieve uniform cell death. Treatment with disinfecting agents such as 2% glutaraldehyde was not considered an option as it can result in extensive cross-linking of the nucleic acids, proteins, and other cellular components that are necessary for the MALDI-TOF MS identification process. Within the past year, two publications described the successful adaptation of a mycobacterial inactivation/ extraction protocol for use with MALDI-TOF MS-based identification (17, 18). Herein, we report a detailed description of an even more convenient process that was first presented in part in 2013 (19). MATERIALS AND METHODSAll studies involving mycobacteria were performed in a biological safety level 3 (BSL-3) laboratory. For various aspects of this study, 28 strains encompass...
This paper deals with open switch Fault Detection and Diagnosis (FDD) in three-level Neutral Point Clamped (NPC) inverter for electrical drives. The approach is based on the already available phase current time series measurements for different operating conditions (motor speed, load, and environment noise). Both fault detection and classification are studied and the efficiency performances of the proposed selected features are shown. For the fault detection, we focus on the first four statistical moments and the extracted features and then the Cumulative Sum (CUSUM) algorithm as the feature analysis technique to improve the performances. For the classification study, we propose to couple the knowledge on the faulty system brought by the statistical moments and the Kullback-Leibler divergence particularly suitable for the detection of incipient changes. The Principal Component Analysis (PCA) is then used to perform the classification. A 2D framework is obtained, which allows the faults to be classified efficiently within the considered operating conditions for all the selected fault durations.
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