Single‐Stage ZVS‐PWM AC‐AC Power Converter Using All SiC Power Module for High‐Frequency Induction Heating Applications

This paper presents a novel prototype of a single‐stage zero voltage soft‐switching pulse‐width modulation ‐controlled ac‐ac converter with a silicon carbide (SiC)‐MOSFET/SiC‐SBD power module for high‐frequency (HF) induction heating (IH) applications. The newly developed ac‐ac converter can achieve higher efficiency than a Si‐IGBT/Si‐PN diode power module‐based prototype due to a low ON‐resistance of SiC‐MOSFET and a low forward voltage of SiC‐SBD under the condition of HF switching. The performances of the new prototype converter are evaluated by experiment with a single‐phase IH utensil of ferromagnetic stainless metal, after which the high‐efficiency and low switching noise characteristics due to the all SiC power module are actually demonstrated.     

A Five‐Element Multiplex Resonant Full‐Bridge DC‐DC Converter with a Variable Inductive Reactance

A five‐element multiplex resonant (LLCLC) full‐bridge DC‐DC converter controlled by pulse frequency modulation (PFM) is proposed in this paper. The high frequency (HF)‐link resonant DC‐DC converter proposed herein can perform wide‐range output power and voltage regulation with a narrow frequency range due to an antiresonant tank that works effectively as a wide‐range variable inductor. The advantageous characteristics of the antiresonant tank provide overcurrent protection in the case of the short‐circuited load condition as well as in the startup interval. Thus, the technical challenges of a conventional LLC DC‐DC converter can be overcome, and the reliability of the relevant switch‐mode power supplies can be improved. The operating principle of the LLCLC DC‐DC converter is described, after which its performance is evaluated in an experimental setup based on the 2.5 kW prototype. Finally, the feasibility of the proposed DC‐DC converter is discussed from a practical point of view.     

Polymers and copolymers of pyrrole and thiophene as electrodes in lithium cells

The performance of pyrrole and thiophene polymer electrodes in lithium cells has been examined in the lithium perchlorate–propylene carbonate electrolyte by cyclic voltammetry. Polypyrrole films were synthesized in 'wet' and 'dry' conditions; pyrrole and thiophene copolymers were prepared at different potentials and bilayers were prepared by sequential deposition of polythiophene (PTh) and polypyrrole (PPy) films. The polymers were cycled between 2.0V and 4.0V in the lithium cells. The effects of disconnecting the electrodes from the cell on the behaviour of the polymers regarding doping and coulombic efficiency were also studied. The cycling performance of the 'wet' PPy is better than 'dry' PPy, bilayer PTh/PPy and copolymers. No mixed behaviour was observed for a bilayer where the inner layer was polythiophene and the outer layer was polypyrrol with a thickness PPy/Pth ratio equal to ten. The copolymer prepared at 3.9V vs Li/Li+ showed the higher energy capacity in Whkg–1 calculated from the anodic charge.     

Effects of docosahexaenoic acid or arachidonic acid supplementation on gene expression and contractile force of rat cardiomyocytes in primary culture

While fatty acids play essential roles in the physiology of the myocardium, conventional culture media contain little lipid. We previously revealed that rat neonatal myocardium mainly contains docosahexaenoic (DHA), linoleic (LA), and arachidonic (AA) acids as polyunsaturated fatty acids (PUFAs), and these contents in cultured cardiomyocytes derived from fetal rats were markedly lower than those in the neonatal myocardium. In this study, we first assessed the effects of supplementation of DHA, LA, or AA on the fatty acid contents and the percentage change of contractile area in primarily cultured rat cardiomyocytes. Based on this assessment, we then evaluated the effects of DHA or AA supplementation on mRNA expression and further directly measured the contractile force of cardiomyocytes with the supplementations. This study revealed that percentage change of contractile area was maximized under 20 μM DHA or 50 μM AA supplementation while LA supplementation did not affect this contraction index, and that a widespread upregulation tendency of the mRNA expression related to differentiation, maturity, fatty acid metabolism, and cell adhesion was seen in the cultured cardiomyocytes with supplementation of DHA or AA. In particular, upregulation of the gene expression of cellular adhesion molecules connexin43 and N-cadherin were remarkable, whereas the effects on differentiation and maturation were less pronounced. Correspondingly, the increase of the percentage change of the contractile area of cardiomyocyte clusters in culture dishes with the supplementations was significant, whereas the enhancement of the contractile force was modest. These results suggest that supplementation of DHA or AA to the fetal cardiomyocyte culture may play effective roles in preventing the de-differentiation of the cardiomyocytes in culture and that the enhancement of the contractile performance may be mainly attributed to the improvement of intercellular connection.