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An improved carrier‐based pulse‐width‐modulation (CBPWM) technique for a three‐level (3L) F‐type neutral point‐clamped (FNPC) inverter is presented in this paper. By using the proposed modulation scheme, the DC‐link capacitor voltage at the neutral point is balanced. For manufacturers, reliability is one of the major concerns for all power electronics devices and parts. This paper proposes an extensive reliability analysis of the 3L‐FNPC inverter. Considering the mean time to failure (MTTF) of each device, the reliability of the 3L‐FNPC inverter is analyzed in this present work by using two different methods, which are the approximate method and the exact method. To compute the failure rate of the equipment, only the number of components is considered in the approximate method. Alternatively, exact methods are utilized to evaluate the reliability of a system by knowing the different stress levels and various operating environments of a specific system. Because of the strong correlation between device failure and temperature stress factors, power loss analysis is used in the exact method. The MATLAB Simulink environment is used to determine the power loss of the switching devices. A solar off‐grid photovoltaic (PV) system is considered for reliability testing. Experimental mission profile data are used to estimate the lifetime of the 3L‐FNPC inverter by applying the rainflow counting algorithm, the Coffin‐Manson model, and Miner's rule. The competitiveness, effectiveness, and reliability of the 3L‐FNPC inverter with the proposed modulation technique are validated using a hardware prototype. [ABSTRACT FROM AUTHOR]

The new μ3‐methoxido bridged trinuclear vanadium(IV) complexes [VIV3O3(μ3‐OMe)(μ2‐OMe)3(L1,2)2] (1 and 2) have been synthesized using the azo ligands 1‐(2‐(thiazol‐2‐yl)diazenyl)naphthalene‐2‐ol (HL1) and 2‐(2‐(thiazol‐2‐yl)diazenyl)‐4‐methylphenol (HL2). X‐ray crystallography revealed a trinuclear structure with a lacunary heterocubane {(VO)3(μ3‐OMe)(μ2‐OMe)3}2+ core unit for complex 1, which contains a central μ3‐methoxido bridge. All three vanadium centers are in a slightly distorted octahedral coordination environment. Magnetic and theoretical studies reveal an antiferromagnetic coupling between the three vanadium(IV) centers within the triangular arrangement in 1. The complexes were also screened for in vitro cytotoxicity study against HeLa and HT‐29 cancer cell lines. The results indicated that both the complexes are cytotoxic but possess varying specificity towards different cell types. [ABSTRACT FROM AUTHOR]

A significant portion of clinically observed antifungal resistance is mediated by ATP‐binding cassette (ABC) and major facilitator superfamily (MFS) transport pumps that reside in the plasma membrane. We review the mechanisms responsible for this phenomenon. Hyper resistance is often brought about by several kinds of DNA amplification or by gain‐of‐function mutations in a variety of transcription factors. Both of these result in overexpression of ABC and MFS transporters. Recently, however, several additional modes of resistance have been observed. These include mutations in non‐conserved nucleotides leading to altered mRNA stability and a mutation in yeast transporter Pdr5, which improves cooperativity between drug‐binding sites. [ABSTRACT FROM AUTHOR]

The utilization of an impedance network in power electronic applications overcame traditional two‐stage converters' drawbacks, including a dc‐dc and dc‐ac stage. A well‐designed impedance‐based converter shuns the necessity of multiple network stages that, in turn, enhance operational performance and reliability. The split source inverter (SSI) belongs to such a single‐stage system that consists of an impedance network with a voltage source inverter. The work's primary purpose is to explore the performance of grid‐connected SSI in the application of wind energy systems. A novel peak power tracking controller is proposed for the SSI‐based wind energy systems for tracking the maximum power available in the wind. The grid‐side controller's current regulator is modified to sense the intermittent wind's perturbation and to regulate the SSI output current. The theoretical analysis is validated by simulation, and different case studies are analyzed by considering the mutual effects of SSI and variable wind speed. A laboratory prototype is designed for the experimental investigation of the SSI that consists of a 5‐kVA three‐phase grid‐tied SSI and wind emulator prototype. A field‐programmable gate array (Xilinx) is used to program the control algorithm. Different test cases are analyzed experimentally to prove the robustness of the proposed controller. [ABSTRACT FROM AUTHOR]

Summary: A dual‐duty digital pulse‐width modulation (DDPWM) technique‐based cost‐effective control hardware architecture for brushless DC (BLDC) motor drive is reported in this paper. DDPWM control technique involves reduced computational complexity, which is beneficial in on‐chip area and power dissipation reduction. Simple Hall sensor‐based speed calculation and commutation circuits were also incorporated in the hardware to reduce the chip area further. The edge detection‐based speed calculation circuit was designed to be tolerant of any external noise or glitch in the Hall sensor signal. The proposed hardware architecture was implemented on the field‐programmable gate array (FPGA) and application‐specific integrated circuit (ASIC) platform using TSMC 180‐nm technology library. The ability of the integrated circuit (IC) for resource utilization reduction was validated by comparing the FPGA‐implemented architecture with the existing literature. The FPGA‐implemented architecture was also examined in real‐time using an experimental prototype BLDC motor setup. The drive response with dynamic load and speed variations, speed control precision, and glitch tolerant speed calculation is reported in the paper. The ASIC implementation demonstrates that the developed architecture sampled at 50 MHz is highly effective in the gate count and power dissipation reduction compared to the standard PI controller‐based width modulated pulse generation hardware architecture. [ABSTRACT FROM AUTHOR]

In conventional grid‐tied renewable energy applications, the dc–dc converter is inevitable. An increased cost, size, and reduced efficiency are the demerits of incorporating a dc–dc converter. A recently introduced split source inverter (SSI) is capable to perform both dc–dc as well as dcac at a time. The main attractive controllable feature of SSI is its modulation index. By utilizing this parameter, an interleaved control structure is proposed for the SSI in grid‐tied photovoltaic applications. The main objectives of the work are to track peak power and to maintain a stabilized voltage across the dc‐link capacitor at a variable load and grid disturbances. The proposed peak power controller performs two important actions: (i) the peak power is traced at all irradiance and (ii) generates a duty cycle to enhance the dc‐link capacitor voltage. The proposed scheme is essentially investigated with simulation. To validate experimentally, a 1 KW photovoltaic system is integrated into a grid‐tied 10 kVA SSI prototype. A Xilinx based Spartan field‐programmable gate array (FPGA) is used to provide a control algorithm for the SSI. Few case studies at different conditions are performed and investigated. Experimental and simulation results are presented to prove the robustness of the control strategy. [ABSTRACT FROM AUTHOR]

This study confers a novel approach towards fuzzy‐PI (proportional–integral) controlled pulse width modulation (PWM) controlled permanent magnet synchronous motor (PMSM) drive operated through a conventional voltage source inverter (VSI) supplemented with buck‐converter fed current source inverter (CSI). It is observed that in a PWM controlled VSI, output voltage and current obtained contains certain harmonic distortion. A buck‐converter fed CSI is capable of minimising the voltage and current ripples prominently even with the application of PWM. Thereby, in this study, an economic, as well as robust design procedure for the buck converter, fed CSI is proposed. Moreover, a particle swarm optimisation (PSO) mechanism is introduced to optimise the performance of the proposed fuzzy logic controller. Additionally, an over‐current protection scheme of the PMSM motor is proposed. The performance of a PMSM drive is analysed in MATLAB/SIMULINK platform. Furthermore, the proposed concept is tested and verified in a real‐time test‐bench developed in the laboratory. Finally, from the performed test conditions, it can be confirmed that the proposed current control strategy of the drive system shows excellent performance in various operating conditions and can be employed in light‐weight electric vehicles. [ABSTRACT FROM AUTHOR]

Drug resistance mechanisms in human pathogenic Candida species are continually evolving. Over the time, Candida species have acquired diverse strategies to vanquish the effects of various classes of drugs thereby, emanating as a serious life threat. Apart from the repertoire of well‐established strategies, which predominantly comprise alteration, overexpression of drug targets, and chromosome duplication, Candida species have evolved a number of permeability constraints for antifungal drugs, via compromised drug import or increased drug efflux. For the latter, genome of Candida species harbour battery of exporters designated as Candida drug resistance genes. These genes predominantly encode membrane efflux transporters, which expel the incoming drugs and thus prevent toxic intracellular accumulation of drugs to manifest multidrug resistance. Such a phenomenon is restricted not only to Candida species but has been observed among many other pathogenic fungal species as well. Notably, the existence of large number of drug exporters in genomes of Candida species posits other pivotal roles for these efflux transporter proteins. The brief review discusses as to how the whole gamut of antifungal research has since been changed to include these new observations wherein reduced permeability of azoles across cell membrane of Candida cells is being implicated as one of the major determinants of antifungal susceptibilities, which all began with the identification of the first multidrug resistance gene CDR1, in Andre Goffeau's laboratory back in 1995. [ABSTRACT FROM AUTHOR]

We present the synthesis, properties, and characterization of [Fe(T1Et4iPrIP)(NO)(H2O)2](OTf)2 (1) {T1Et4iPrIP = Tris(1‐ethyl‐4‐isopropyl‐imidazolyl)phosphine} as a model for the nitrosyl adduct of gentisate 1,2‐dioxygenase (GDO). The further characterization of [Fe(T1Et4iPrIP)(THF)(NO)(OTf)](OTf) (2) which was previously communicated (Inorg. Chem. 2014, 53, 5414) is also presented. The weighted average Fe–N–O angle of 162° for 1 is very close to linear (≥ 165°) for these types of complexes. The coordinated water ligands participate in hydrogen bonding interactions. The spectral properties (EPR, UV/Vis, FTIR) for 1 are compared with 2 and found to be quite comparable. Complex 1 closely follows the relationship between the Fe–N–O angle and NO vibrational frequency which was previously identified for six‐coordinate {FeNO}7 complexes. Liquid FTIR studies on 2 indicate that the ν(NO) vibration position is sensitive to solvent shifting to lower energy (relative to the solid) in donor solvent THF and shifting to higher energy in dichloromethane. The basis for this behavior is discussed. The Keq for NO binding in 2 was calculated in THF and found to be 470 m–1. Density functional theory (DFT) studies on 1 indicate donation of electron density to the iron center from the π* orbitals of formally NO–. Such a donation accounts for the near linearity of the Fe–N–O bond and the large ν(NO) value of 1791 cm–1. We report a model for the iron–nitrosyl adduct of gentisate dioxygenase {[Fe(T1Et4iPrIP)(NO)(H2O)2](OTf)2, 1}. Complex 1 is synthesized by the addition of 2 equiv. water to [Fe(T1Et4iPrIP)(THF)(NO)(OTf)](OTf) (2). A correlation between the solid‐state Fe–N–O angle and ν(NO) is elaborated and the Keq in THF for the reversible binding of NO to 2 is reported. The influence of solvent on the value of ν(NO) for 2 is also discussed. [ABSTRACT FROM AUTHOR]

We previously reported the spin-crossover (SC) properties of [FeII(tacn)2](OTf)2 (1) (tacn = 1,4,7-triazacyclononane). Upon heating under dynamic vacuum, 1 undergoes oxidation to generate a low-spin iron(III) complex. The oxidation of the iron center was found to be facilitated by initial oxidation of the ligand through loss of a H atom. The resulting complex was hypothesized to have the formulation [FeIII(tacn)(tacn-H)](OTf)2 (2) where tacn-H is N-deprotonated tacn. The formulation was confirmed by ESI-MS. The powder EPR spectrum of the oxidized product at 77 K reveals the formation of a low-spin iron(III) species with rhombic spectrum (g = 1.98, 2.10, 2.19). We have indirectly detected H2 formation during the heating of 1 by reacting the headspace with HgO. Formation of water (1H NMR in anhydrous [D6]DMSO) and elemental mercury were observed. To further support this claim, we independently synthesized [FeIII(tacn)2](OTf)3 (3) and treated it with one equivalent of base yielding 2. The structures of 3 were characterized by X-ray crystallography. Compound 2 also exhibits a low-spin iron(III) rhombic signal (g = 1.97, 2.11, 2.23) in DMF at 77 K. Variable temperature magnetic susceptibility measurements indicate that 3 undergoes gradual spin increase from 2 to 400 K. DFT studies indicate that the deprotonated nitrogen in 2 forms a bond to iron(III) exhibiting double-bond character (Fe–N, 1.807 Å). [ABSTRACT FROM AUTHOR]

The synthesis and characterization of [Co(T1Et4 iPrIP)X2] {T1Et4 iPrIP = tris(1-ethyl-4-isopropylimidazolyl)phosphine; X = OTf- ( 1), Cl- ( 2), Br- ( 3)} and [Co(T1Et4 iPrIP)(CH3CN)3](OTf)2 ( 4) were investigated. In compounds 1 and 4, T1Et4 iPrIP binds in a tridentate fashion, whereas 2 and 3 feature bidentate ligation. Compound 1 additionally coordinates two triflate ligands to complete a distorted square pyramidal geometry. Compound 4 also binds three acetonitrile ligands to afford a distorted octahedral geometry. Compounds 2 and 3 exhibit a distorted tetrahedral geometry for which the ligands comprise two imidazole nitrogen atoms and two halides. Bidentate coordination by using a tris(imidazolyl)phosphine ligand is unprecedented. Compounds 2 and 3 can be derived from 1 by the addition of either Cl- or Br- salts, respectively, whereas 4 can be generated by dissolving 1 in acetonitrile. DFT studies indicate that the HOMO-LUMO gaps of all compounds are comparable; however, steric factors stabilize the formation of 2 and 3 over 1 in the presence of halide ligands. [ABSTRACT FROM AUTHOR]

The synthesis and structure of [MnLCl]0.5H2O ( 1·0.5H2O, HL = 1-benzyl-4-acetato-1,4,7-triazacyclononane) is reported. Complex 1 exists as a coordination polymer in the solid state, and the MnII center is bonded to three amine nitrogen atoms, one carboxylate oxygen atom, a chlorido ligand, and an adjacent carboxylate group in a chelating fashion to afford a seven-coordinate center. The dissolution of 1 in acetonitrile containing excess oxalate (ox) ions results in a monomeric species. When mixtures of 1 and oxalate ions are exposed to oxygen under ambient conditions, a dark pink EPR-silent species is generated. The pink species is believed to be [MnIII(ox)2]-, which results from the displacement of the ligand L- by an oxalate ion. The decomposition of this species ultimately results in the formation of 1 equiv. of CO2 per oxalate ion consumed, a HCO3- ion, and a MnII species. Further reaction of the resulting MnII species with excess oxalate in the presence of oxygen leads to additional oxalate degradation. [ABSTRACT FROM AUTHOR]

The structures of [FeII(tacn)2](OTf)2 ·DMF ( 1·DMF), [FeII(tacd)2](OTf)2 ( 2), and [FeII(tacud)2](OTf)2 ( 3) (OTf = triflate, tacn = 1,4,7-triazacyclononane, tacd = 1,4,7-triazacyclodecane, tacud = 1,4,8-triazacycloundecane) are reported. In the solid state, compounds 1 and 2 exhibit temperature-dependent gradual and reversible one-step spin crossover between the high-spin ( S = 2) and low-spin ( S = 0) states with estimated spin-conversion equilibria ( T1/2) of 330 and 320 K, respectively. Compound 1 exhibits somewhat reversible magnetic behavior during the heating and cooling cycle, whereas 2 is more reversible. Compound 2 is only the third example of a spin-crossover compound possessing secondary amine ligands exclusively. Complex 3 is high spin at the temperatures measured. Systematic comparison of the properties of 1- 3 indicates that the structural-magnetic properties correlate with the ligand-donor strength. There is also a close correlation with the room-temperature solution spin state and E1/2 in acetonitrile for these compounds. [ABSTRACT FROM AUTHOR]

The structures of [FeIII(tacud)Cl3] ( 1) and [FeIII(tacn)Cl3] ( 2) (tacud = 1, 4, 8-triazacycloundecane, tacn = 1, 4, 7-triazacyclononane) are reported. Both compounds crystallize in the orthorhombic space group Pnma with a = 12.5570(9), b = 12.0028(9), c = 8.2577(6) Å, V = 1244.59(16) Å3, and Z = 4 for 1 and a = 12.095(4), b = 11.125(4), c = 7.963(3) Å, V = 1071.5(6) Å3, and Z = 4 for 2. The structures of 1 and 2 feature iron(III) in distorted octahedral arrangement with three facially coordinated nitrogen ligands and three chlorides. Bidirectional intermolecular hydrogen bonding between N-H groups and coordinated chlorides is seen for 1 and 2. Compound 1 is the first example of iron(III) bonded to tacud and compound 2 is only the second structure reported of a 1:1 complex between iron and tacn. The Fe3+/2+ redox couple for 1 is observed at E1/2 = 0.25 V (Δ Ep = 99 mV), and for 2 at E1/2 = 0.09 V (Δ Ep = 108 mV) versus NHE in DMF at 298 K. Comparison of structural, magnetic, and electrochemical properties for 1 and 2 reveal subtle differences consistent with the stronger coordinating properties of tacn relative to tacud. [ABSTRACT FROM AUTHOR]