The two-component signal transduction system CpxAR is especially widespread in Gram-negative bacteria. It has been reported that CpxAR contributes to the multidrug resistance (MDR) in Escherichia coli. CpxR is a response regulator in the two-component CpxAR system. The aim of this study was to explore the role of cpxR in the MDR of S. enterica serovar Typhimurium. The minimal inhibitory concentrations (MICs) of various antibiotics commonly used in veterinary medicine for strains JS (a multidrug-susceptible standard strain of S. enterica serovar Typhimurium), JSΔcpxR, JSΔcpxR/pcpxR, JSΔcpxR/pcpxR*, JSΔcpxRΔacrB, JSΔcpxRΔacrB/pcpxR, JSΔcpxRΔacrB/pcpxR*, 9 S. enterica serovar Typhimurium isolates (SH1–9), and SH1–9ΔcpxR were determined by the 2-fold broth microdilution method. The relative mRNA expression levels of ompF, ompC, ompW, ompD, tolC, acrB, acrD, acrF, mdtA, marA, and soxS in strains JS, JSΔcpxR, and JSΔcpxR/pcpxR were detected by real-time PCR. The results showed 2- to 4-fold decreases in the MICs of amikacin (AMK), gentamycin (GEN), apramycin (APR), neomycin (NEO), ceftriaxone (CRO), ceftiofur (CEF), and cefquinome (CEQ) for strain JSΔcpxR, as compared to those for the parental strain JS. Likewise, SH1–9ΔcpxR were found to have 2- to 8-fold reduction in resistance to the above antibiotics, except for NEO, as compared to their parental strains SH1–9. Furthermore, 2- to 4-fold further decreases in the MICs of AMK, GEN, APR, and CEF for strain JSΔcpxRΔacrB were observed, as compared to those for strain JSΔacrB. In addition, CpxR overproduction in strain JSΔcpxR led to significant decreases in the mRNA expression levels of ompF, ompC, ompW, ompD, tolC, acrB, marA, and soxS, and significant increases in those of stm3031 and stm1530. Notably, after all strains were induced simultaneously by GEN to the 15th passage at subinhibitory concentrations, strain JSΔcpxR/pcpxR showed significant increases in mRNA expression levels of the efflux pump acrD and mdtA genes, as compared to strain JSΔcpxR. Our results indicate that the two-component regulator CpxR contributes to resistance of S. enterica serovar Typhimurium to aminoglycosides and β-lactams by influencing the expression level of the MDR-related genes.

Because of the strong photoabsorption of porphyrin and its derivatives in the visible light region, composites of porphyrin−carbon nanotubes show promise as materials for photovoltaic and photoenergy transfer applications. Studies have reported the photoexcited states of functionalized carbon nanotube composites containing externally attached porphyrin. However, the photoexcited states of carbon nanotube composites containing encapsulated porphyrin moieties have not been investigated. The enhancement of photostability and chemical stability of porphyrins, which is crucial in device applications, is expected in these composites. In this study, we fabricated a composite of single-walled carbon nanotubes and encapsulated porphyrins to investigate ultrafast relaxation dynamics of photoexcited states by steady-state measurements and femtosecond time-resolved measurements. We found that excitation energy transfer by electron exchange via two-step electron transfer between the encapsulated porphyrin and single-walled carbon nanotube occurs in the femtosecond regime. This study provides an insight into photovoltaic functionality and photoenergy transfer in molecule-encapsulating materials.

We have developed a simple and straightforward way to realize controlled post-doping towards 2D transition metal dichalcogenides (TMDs). The key idea is to use low-kinetic energy dopant beams and a high-flux chalcogen beam at the same time, leading to substitutional doping with controlled dopant densities. Atomic-resolution transmission electron microscopy has revealed that dopant atoms injected toward TMDs are incorporated substitutionally into the hexagonal framework of TMDs. Electronic properties of doped TMDs (Nb-doped WSe2) have shown drastic change, p-type action with more than two orders of magnitude increase in on current. Positionselective doping has also been demonstrated by the post-doping toward TMDs with a patterned mask on the surface. The post-doping method developed in this work can be a versatile tool for 2D-based next-generation electronics in the future.

Using the density functional theory, we study the geometric and electronic structures of a GaN sheet possessing a honeycomb network. The sheet preserves the planar conformation under an equilibrium lattice constant of 3.2 Å, possessing a semiconducting electronic structure with an indirect band gap of 2.28 eV. The biaxial compressive strain causes structural buckling, leading to polarization normal to the atomic layer. An external electric field normal to the layer also induces structural buckling whose height is proportional to the field strength. The polarity of the buckled GaN sheet is tunable by attaching H atoms on Ga and N atoms.

as they provide a novel platform for studying both fundamental physics and device applications. [1,2] VdW heterostructures offer new routes for achieving novel physical properties at the interfaces between individual 2D layers. Vertically stacked 2D materials, such as graphene and transition metal dichalcogenides (TMDs), with a twisted angle or a lattice mismatch in the artificial vdW heterostructures can lead to the formation of moiré patterns (moiré superlattices) because of their spatially varying atomic registry, which gives rise to intense physical phenomena, including a strongly correlated insulator phase, [3,4] superconductivity, [5] and moiré excitons. [6][7][8] Here, excitons arising from bound electron-hole pairs through the Coulomb interaction are confined in the periodic potential of moiré patterns. Moreover, both intralayer and interlayer excitons formed by layer-locked and layer-separated bound electrons and holes, respectively, exhibit pronounced moiré signatures in semiconducting bilayer TMD vdW heterostructures. [8][9][10] The intralayer and interlayer excitons modulated by the moiré potential result in a spatially organized array of exciton ensemble in the moiré superlattice. Moiré excitons in moiré superlattices offer the possibility to study quantum simulations of many-body systems and dense arrays of coherent quantum emitters, which could be useful for applications in quantum optics.Since the discovery of 2D layered ferromagnetic and antiferromagnetic materials, the intriguing magnetic properties of 2D materials have attracted considerable interest in the research field of material science. Among 2D layered magnetic materials, transition metal phosphorous dichalcogenides (TMPX 3 ; TM = Mn, Ni, Fe, Co; X = S, Se) have been extensively studied as a model system of layered magnetic materials. [11,12] For instance, free excitons coupled to magnons were reported in both bulk antiferromagnetic MnPS 3 [13] and heterostructures composed of semiconducting MoSe 2 and antiferromagnetic MnPSe 3 . [14] Moreover, novel excitons with an ultra-narrow photo luminescence (PL) peak were found in bulk NiPS 3 ; [15][16][17] these excitons arise from the many-body states of Zhang-Rice singlets and reach a coherent state assisted by the antiferromagnetic order. [17] However, the interaction between moiré excitonic states (excitons and trions) and magnetic elementary excitations in magnetic materials has yet to be experimentally studied. To Moiré fringe patterns created by stacking different 2D layered materials as artificial van der Waals (vdW) heterostructures have become a novel platform to study and engineer optically generated excitonic properties. The moiré patterns contribute to the formation of spatially ordered excitonic states (excitons and trions), which can be used in the quantum simulation of many-body systems and ensembles of coherent quantum light emitters. The intriguing moiré excitonic properties are affected by and controlled via the interaction with magnetic elements. Here, a moiré excitonic syste...