Charge-remote fragmentation during FAB-CAD-B/E linked-scan mass spectrometry of aminoethyl-triphenylphosphonium derivatives of fatty acids

AbstractThe carboxyl group of fatty acids is derivatized by aminoethyl triphenylphosphonium (AETPP) bromide. Fast atom bombardment (FAB) collision-activated dissociation (CAD) B/E linked-scan mass spectrometry of these fixed-charge derivatives shows typical charge-remote fragmentation (CRF). Locations of various structural modifications in fatty acids can be recognized easily from CAD spectra of the AETPP derivatives. Because the triphenylphosphonium group localizes positive charge in the molecule, and because a key requirement for CRF is tightly localized charge site, these preionized molecules fragment under FAB-CAD conditions more effectively than other derivatives that involve ionic bonding with metal cations or protonation of basic sites. Thus, CAD of AETPP derivatives is likely to produce more structurally informative spectra and provide an opportunity to gain additional understanding of the CRF process. The most profound difference between the AETPP derivatives and other cations in positive mode FAB-CAD-B/E-MS is reflected in the substantial improvement of detection limits for the AETPP derivatives over those for the metal cation adducts. For several fatty acids (C10C22) tested, the detectability can be enhanced by one to two orders of magnitude when the analysis is performed on the AETPP derivative. In addition, for the analysis of fatty acid mixtures, the FAB mass spectrum of AETPP derivatives produces a relative intensity of the molecular ion peak for each component of the mixture that more closely represents its mole fraction than does that of metal ion adducts

High-efficiency Bidirectional Buck-Boost Converter for Residential Energy Storage System

This paper proposes a bidirectional dc-dc converter for residential micro-grid applications. The proposed converter can operate over an input voltage range that overlaps the output voltage range. This converter uses two snubber capacitors to reduce the switch turn-off losses, a dc-blocking capacitor to reduce the input/output filter size, and a 1:1 transformer to reduce core loss. The windings of the transformer are connected in parallel and in reverse-coupled configuration to suppress magnetic flux swing in the core. Zero-voltage turn-on of the switch is achieved by operating the converter in discontinuous conduction mode. The experimental converter was designed to operate at a switching frequency of 40-210 kHz, an input voltage of 48 V, an output voltage of 36-60 V, and an output power of 50-500 W. The power conversion efficiency for boost conversion to 60 V was >= 98.3% in the entire power range. The efficiency for buck conversion to 36 V was >= 98.4% in the entire power range. The output voltage ripple at full load was <3.59 V-p.p for boost conversion (60 V) and 1.35 V-p.p for buck conversion (36 V) with the reduced input/output filter. The experimental results indicate that the proposed converter is well-suited to smart-grid energy storage systems that require high efficiency, small size, and overlapping input and output voltage ranges.11Ysciescopu

Safety and tissue yield for percutaneous native kidney biopsy according to practitioner and ultrasound technique

BACKGROUND: Although percutaneous renal biopsy remains an essential tool in the diagnosis and treatment of renal diseases, in recent times the traditional procedure of nephrologists has been performed by non-nephrologists rather than nephrologists at many institutions. The present study assessed the safety and adequacy of tissue yield during percutaneous renal biopsy according to practitioners and techniques based on ultrasound. METHODS: This study included 658 native renal biopsies performed from 2005 to 2010 at a single centre. The biopsies were performed by nephrologists or expert ultrasound radiologists using the ultrasound-marked blind or real-time ultrasound-guided techniques. RESULTS: A total of 271 ultrasound-marked blind biopsies were performed by nephrologists, 170 real-time ultrasound-guided biopsies were performed by nephrologists, and 217 real-time ultrasound-guided biopsies were performed by radiologists during the study period. No differences in post-biopsy complications such as haematoma, need for transfusion and intervention, gross haematuria, pain, or infection were observed among groups. Glomerular numbers of renal specimens from biopsies performed by nephrologists without reference to any technique were higher than those obtained from real-time ultrasound-guided biopsies performed by expert ultrasound radiologists. CONCLUSIONS: Percutaneous renal biopsy performed by nephrologists was not inferior to that performed by expert ultrasound radiologists as related to specimen yield and post-biopsy complications