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Fluorides and their CO 2 mixtures are considered as promising choices of SF 6 -substitute gases due to their low global warming potentials and high dielectric strength. This paper investigates physical and chemical properties and breakdown characteristics of different common fluorides and their mixtures for application in the power system. For dielectric characteristics of fluorides and their mixtures, their power frequency breakdown voltages are determined experimentally, and the results are compared with SF 6 . For physical and chemical characteristics, the saturated vapor pressures, global warming potentials (GWPs), toxicities, prices of fluorides and their mixtures are calculated, and the corresponding characteristic curves are obtained. Based on characteristics mentioned above, a method for obtaining the optimal gas parameters of a specific fluoride mixture is proposed, which can be used as a feasible solution to find an SF 6 alternative gas that meets the application requirements. The results show that CO 2 mixtures with hexafluoropropene (HFP), 1,1,1,2-tetrafluoroethane (HFC-134a) and perfluoroisobutyronitrile (C4-PFN) are three types of good SF 6 -substitute gases. HFP/CO 2 mixtures with HFP component ratios 0.32 to 0.6 are suitable for applications at 0.1 to 0.3 MPa. HFC-134a/CO 2 mixtures (HFC-134a component ratios from 0.16 to 0.2) are suitable for applications at 0.3 to 0.5 MPa. C4-PFN/CO 2 mixtures (C4-PFN component ratios from 0.09 to 0.12) could be used for the applications at 0.1 to 0.5 MPa, regardless of the gas price. [ABSTRACT FROM AUTHOR]

In this study, particle swarm optimisation (PSO) is applied to determine the Heidler's function parameters (HFPs) for approximating the measured full lightning channel‐base‐current (CBC) of the severe (5% data in IEC standard 62305‐1, 2010) negative first return stroke (NFS) and subsequent return stroke (NSS). The parameters in the sum of two Heidler's functions, namely I01, I02, τ11, τ12, τ21, τ22, n1, and n2, are identified using PSO as a tool. The HFPs for severe NFS and NSS are tuned to keep four parameters constant with systematic variation of one out of all prominent parameters (i.e. peak current (Im), maximum time rate of change of current ((di/dt)max), front duration (tFD), stroke duration (tSD), and total charge (Q)) of full CBC wave and vice versa. The corresponding data is reported, and an independent controlling of HFPs is analysed to achieve the desired full CBC wave. Also, an attempt has been made in this study to examine the interdependence between the wavefront and tail of CBC using PSO. The data thus generated and reported for severe NFS and NSS can be used to generate the suitable full CBC waveforms. This methodology will be helpful in lightning‐related simulation study and research. [ABSTRACT FROM AUTHOR]

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Mammalian FIR has dual roles in pre-mRNA splicing and in negative transcriptional control of Myc. Here we show that Half pint (Hfp), the Drosophila orthologue of FIR, inhibits cell proliferation in Drosophila. We find that Hfp overexpression potently inhibits G1/S progression, while hfp mutants display ectopic cell cycles. Hfp negatively regulates dmyc expression and function, as reducing the dose of hfp increases levels of dmyc mRNA and rescues defective oogenesis in dmyc hypomorphic flies. The G2delay in dmyc-overexpressing cells is suppressed by halving the dosage of hfp, indicating that Hfp is also rate-limiting for G2-M progression. Consistent with this, the cycle 14 G2-arrest of stg mutant embryos is rescued by the hfp mutant. Analysis of hfp mutant clones revealed elevated levels of Stg protein, but no change in the level of stg mRNA, suggesting that hfp negatively regulates Stg via a post-transcriptional mechanism. Finally, ectopic activation of the wingless pathway, which is known to negatively regulate dmyc expression in the wing, results in an accumulation of Hfp protein. Our findings indicate that Hfp provides a critical molecular link between the developmental patterning signals induced by the wingless pathway and dMyc-regulated cell growth and proliferation. [ABSTRACT FROM AUTHOR]