77 research outputs found

    A Review of Voltage-Clamping Methods for Solid-State Circuit Breakers

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    In recent years, the interest in DC systems has increased dramatically because of some key advantages, in terms of efficiency and reliability, that this technology can offer compared to AC systems in applications such as shipboard distribution, more electric aircrafts, DC microgrids, battery protection, and photovoltaics. In this context, DC circuit breakers based on power semiconductors, the so-called solid-state circuit breakers, are becoming a popular choice because of their fast intervention speed, which is typically on the order of microseconds. Unfortunately, power electronics are vulnerable to 'breakdown', which is a dangerous operating condition triggered by overvoltages. During current interruption, the energy stored in the inductive elements of the system must be dissipated, and this typically creates a very high voltage spike on the interrupting component, which is the breaker pole. This phenomenon, if not controlled, could lead to the premature failure of the semiconductor inside the solid-state circuit breaker. For this reason, suitable techniques aimed to control the voltage gradient and overshoot during interruption have been presented in the literature. This paper analyzes and compares the performances of the voltage-clamping solutions presented in the technical literature, which range from simple passive devices to more advanced solutions

    Mefloquine versus quinine plus sulphalene-pyrimethamine (metakelfin) for treatment of uncomplicated imported falciparum malaria acquired in Africa

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    We conducted a multicenter, randomized, open-label trial to compare mefloquine with a 3-day quinine plus sulphalene-pyrimethamine (SP) regimen for the treatment of imported uncomplicated malaria acquired in Africa. The end points of the study were efficacy, tolerability, and length of hospital stay. From July 1999 to February 2003, 187 patients were enrolled in five centers in Italy, of whom 93 were randomized to receive mefloquine (the M group) and 94 were randomized to receive quinine plus SP (the QSP group). Immigrants and visiting relatives and friends represented 90% of the cases and were mainly from western African countries. A slightly increased proportion of cases in the QSP group had abnormal alanine aminotransferase levels at the baseline. The early cure rate was similar in the two groups: 98.9% (confidence interval [CI] = 97 to 100%) in the M group and 96.8% (CI = 93 to 100%) in the QSP group. The extended follow-up was completed by 135 subjects (72.2%), and no case of recrudescence was detected. There were no differences in the parasite clearance time, but patients in the M group had shorter mean fever clearance time (35.9 h versus 44.4 h for the QSP group; P = 0.05) and a shorter mean hospital stay (3.9 days versus 4.6 days for the QSP group; P = 0.007). The overall proportions of reported side effects were similar in the two groups, but patients in the M group had a significantly higher rate of central nervous system disturbances (29.0% versus 9.6% for the QSP group; P < 0.001)

    Optimal flux reference to operate a five-phase induction machine under two open-phase fault condition

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    Electrical drives are largely adopted in industry and in the last years, thanks to the increased awareness towards the environment, they are spreading as a means for transport. The most common electrical machines are three-phase and their construction is well known. However, for a three-phase machine the first fault on one phase of either the machine or the inverter implies the impossibility to develop a torque causing the stop of the machine. Multiphase machines among all the different advantages allow to keep operating until three phases are healthy. For this reason, these types of machines are spreading in all the applications for which the continuity of service is necessary. In this paper a five-phase induction machine is considered. In particular, for this machine, the working conditions with two faulted open phases is studied and the optimal reference for the machine flux is evaluated together with the maximum allowable torque. Both the cases of adjacent and non-Adjacent faulted phases are analyzed and the results are proven by means of numerical simulations

    Characterization of rem genes involved in the reproductive development of arabidopsis thaliana

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    The REM transcriptional factor family belongs to the plant-specific B3 DNA binding domain superfamily, in Arabidopsis thaliana this family is composed of 45 genes preferentially expressed during flower and seed development among which only a few members have been associated to a function. We focused our attention on three homologous members of this family, REM34 , REM35 and REM36, which are expressed in the inflorescence meristem and in the earliest stages of flower development. To uncover their role RNA interference lines for the simultaneous silencing of these three genes were analysed. At the same time, a CRISPR/Cas9 approach was chosen in order to generate single and multiple mutants. The RNAi lines and the CRISPR/Cas9 mutants showed an aberrant phyllotaxis, a higher rate of flower production and, only in the RNAi lines, an arrest in the female gametophyte in the FG1/FG2 phase. YUCCA1 , which is coexpressed with REM34 and its closest homologs YUC4 , and YUC6 were found to be downregulated in these RNAi lines. These genes code for flavin monooxygenase proteins involved in auxin biosynthesis and their mutation or misregulation phenocopies RNAi lines. All these evidence suggest that REM34 , REM35 and REM36 could be involved in the regulation of auxin biosynthesis at the level of the inflorescence and flower meristem

    Assessing the role of REM13, REM34 and REM46 during the transition to the reproductive phase in Arabidopsis thaliana

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    REM (reproductive meristem) transcription factors have been proposed as regulators of plant reproductive development mainly based on their specific expression patterns in reproductive structures, but their roles are still largely unknown probably because of their redundancy. We selected three REM genes (REM13, REM34 and REM46) for functional analysis, based on their genome position and/or co-expression data. Our results suggest that these genes have a role in flowering time regulation and may modulate cell cycle progression. In addition, protein interaction experiments revealed that REM34 and REM46 interact with each other, suggesting that they might work cooperatively to regulate cell division during inflorescence meristem commitment. Previous attempts of using co-expression data as a guide for functional analysis of REMs were limited by the transcriptomic data available at the time. Our results uncover previously unknown functions of three members of the REM family of Arabidopsis thaliana and open the door to more comprehensive studies of the REM family, where the combination of co-expression analysis followed by functional studies might contribute to uncovering the biological roles of these proteins and the relationship among them
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