Search

Antimicrobial peptides that act by disrupting bacterial membranes are attractive agents for treating drug-resistant bacteria. This study investigates a membrane-disrupting peptide mimic made of a cyclic oligosaccharide cyclodextrin scaffold that can be chemically polyfunctionalized. An antibacterial functional group on the peptide was simplified to an alkylamino group that combines cationic and hydrophobic moieties, the former to interact with the anionic bacterial membrane and the latter with the membrane interior. The cyclodextrins equipped with eight alkylamino groups on the molecules using a poly-click reaction exhibited antibacterial activity against Gram-positive and Gram-negative bacteria, including drug-resistant pathogens such as carbapenem-resistant Enterobacteriaceae. Several lines of evidence showed that these agents disrupt bacterial membranes, leading to rapid bacterial cell death. The resulting membrane perturbation was directly visualized using high-speed atomic force microscopy imaging. In Gram-negative bacteria, the membrane-permeabilizing action of these derivatives allowed the entry of co-treated traditional antibiotics, which were then active against these bacteria.

We developed a near-infrared (NIR) superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) and demonstrated high-axial-resolution optical coherence tomography (OCT) imaging using this QD-based SLD (QD-SLD). The QD-SLD utilized InAs QDs with controlled emission wavelengths as a NIR broadband light emitter, and a tilted waveguide with segmented electrodes was prepared for edge-emitting broadband electroluminescence (EL) spanning approximately 1–1.3 μm. The bandwidth of the EL spectrum was increased up to 144 nm at a temperature of 25 °C controlled using a thermoelectric cooler. The inverse Fourier transform of the EL spectrum predicted a minimum resolution of 3.6 μm in air. The QD-SLD was subsequently introduced into a spectral-domain (SD)-OCT setup, and SD-OCT imaging was performed for industrial and biological test samples. The OCT images obtained using the QD-SLD showed an axial resolution of ~4 μm, which was almost the same as that predicted from the spectrum. This axial resolution is less than the typical size of a single biological cell (~5 μm), and the practical demonstration of high-axial-resolution OCT imaging shows the application of QD-SLDs as a compact OCT light source, which enables the development of a portable OCT system.

Herein, we report an emission wavelength control technique for self-assembled InAs quantum dots (QDs) grown via molecular beam epitaxy using an As2 source (As2-QDs). The As2-QDs exhibited photoluminescence with a shorter center wavelength and larger bandwidth than those of the QDs grown using an As4 source. In addition, the emission center wavelength could be controlled by adjusting the time between the growth and capping of the As2-QDs. We utilized the multilayer stack of emission-wavelength-controlled As2-QDs to fabricate an electrically-driven light source and demonstrated its broadband (approximately 130 nm) emission in the 1–1.3 μm wavelength range.

This paper presents a novel control scheme for the modular matrix converter (MMxC), in terms of balancing capacitor voltages in addition to controlling output voltage and input current along with a comprehensive mathematical model. The proposed technique has been designed based on a fully decoupled current control of the positive-, negative-, and zero-sequence components of each MMxC subconverter in addition to the feedforward instantaneous power control to suppress the capacitor voltages fluctuation. The frequency of the zero-sequence is the output frequency for the load. Therefore, the positive-sequence current component is used to control the input current to achieve unity input power factor, the negative-sequence current component is used to balance the capacitor voltages among all MMxC arms, and the zero-sequence current component is used to control the output voltage. The effectiveness of the proposed control scheme for controlling the MMxC has been verified theoretically, using simulation software, and experimentally, using a laboratory prototype based 3 kVA, 200 V.

We obtained a high-intensity and broadband emission centered at ~1 µm from InGaAs quantum three-dimensional (3D) structures grown on a GaAs substrate using molecular beam epitaxy. An InGaAs thin layer grown on GaAs with a thickness close to the critical layer thickness is normally affected by strain as a result of the lattice mismatch and introduced misfit dislocations. However, under certain growth conditions for the In concentration and growth temperature, the growth mode of the InGaAs layer can be transformed from two-dimensional to 3D growth. We found the optimal conditions to obtain a broadband emission from 3D structures with a high intensity and controlled center wavelength at ~1 µm. This method offers an alternative approach for fabricating a broadband near-infrared light source for telecommunication and medical imaging systems such as for optical coherence tomography.

SiC-MOSFETs have attracting increasing attention because of their outstanding characteristics that contributes to high efficiency and high power density of power converters. However, compared to conventional Si-IGBTs, SiC-MOSFETs are susceptible to false triggering, because they tend to generate large switching noise due to ultrafast switching capability and have a lower threshold voltage in high temperature operation. Particularly, disastrous oscillation of repetitive false triggering can occur after a fast turn-off, which is the severe issue for practical application of SiC-MOSFETs. The purpose of this paper is to give an instruction to avoid this phenomenon. This paper hypothesized that the repetitive false triggering is the parasitic oscillation caused by parasitic capacitance of SiC-MOSFET, and parasitic inductance of wiring. Based on this hypothesis, this paper analyzed the oscillatory condition of the parasitic oscillator to propose a design instruction to avoid the oscillatory false triggering. The result revealed that the parasitic inductance of the gate, drain, and source wiring should be designed so that the resonance frequency of the parasitic LC resonator in the gating circuit is far apart from that of the power circuit. This paper also presents experimental results that support appropriateness of the proposed design instruction.

InAs quantum dots (QDs) were grown on GaAs by molecular beam epitaxy using As 2 molecules (As 2 -QDs) and were structurally and optically characterized. Photoluminescence (PL) measurements revealed unique optical properties of the As 2 -QDs, which differ from InAs QDs grown with As 4 (As 4 -QDs). As 2 -QDs exhibited PL emission centered at 1.14–1.21 µm, which is shorter than that of As 4 -QDs (1.21–1.22 µm). In addition, the emission peak wavelength was continuously redshifted with a growth interruption time (Δt), which is an interval between the growth of the As 2 -QDs and capping of the QDs with a GaAs layer. Considering that no apparent difference of structural property was observed among as-grown As 2 -QDs and As 4 -QDs with various Δt, the peak shift can be attributed to the deformation of QDs during the capping process. The continuous peak shift can be applied to control the emission wavelength of InAs QDs, and this enables a broadband light source by combining the As 2 -QDs with different peak wavelengths.

Recently various kinds of free-formed single-layer latticed shell structures with glass surface are realized in Europe for covering public open spaces. The connection system for such structure requires out-of-plane strength and stiffness, and the buckling stability of such structures is affected by the stiffness of the connections. In this report, simple connection system composed of hollow-cylindrical nodes and tension bolts is proposed. The stiffness and strength of proposed connections against out-of-plane bending, in-plane bending, compression, and tension forces are confirmed by experiments, and the effects on the buckling strength of sample structure are discussed.

This paper presents a novel control method for controlling the Modular Matrix Converter (MMxC) in order to achieve balanced capacitor voltages in addition to load voltage and input current control. The proposed control technique has been designed based on independent current control of positive-, negative- and zero-sequence in addition to feed forward power control. The positive-sequence circuit is used to control the input current, the negative-sequence circuit is used to balance the capacitor voltage among MMxC arms and the zero-sequence circuit is used to control the load control. Feed forward power control is used to suppress the capacitor voltage fluctuation. The effectiveness of the proposed control scheme for the MMxC has been verified theoretically using simulation software and experimentally using 4kVA–200V laboratory prototype.

This paper presents independent control of input current and output voltage for Modular Matrix Converter (MMxC). The MMxC is a multi-level converter without a transformer that converts from the high voltage AC to high voltage AC with arbitrary amplitude and frequency. The control method is difficult due to the simultaneous control of the input current and output voltage. The authors propose a novel control method that is divided into two parts of the positive-sequence circuit for the input current control, and the zero-sequence circuit for the output voltage control. The effectiveness of the proposed control method has been verified by simulations and experiments.