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A periodic electric field of light applied on a solid is predicted to generate coupled states of the light electric fields and electronic system called photon-dressed Floquet states. Previous studies of those Floquet states have focused on time-averaged energy-level structures. Here, we report time-dependent responses of Floquet states of excitons generated by a mid-infrared (MIR) pulse excitation in a prototypical one-dimensional (1D) Mott insulator, a chlorine-bridged nickel-chain compound, [Ni(chxn) 2 Cl](NO 3 ) 2 (chxn = cyclohexanediamine). Sub-cycle reflection spectroscopy on this compound using a phase-locked MIR pump pulse and an ultrashort visible probe pulse with the temporal width of ∼7 fs revealed that large and ultrafast reflectivity changes occur along the electric field of the MIR pulse; the reflectivity change reached approximately 50% of the original value around the exciton absorption peak. It comprised a high-frequency oscillation at twice the frequency of the MIR pulse and a low-frequency component following the intensity envelope of the MIR pulse, which showed different probe-energy dependences. Simulations considering one-photon-allowed and one-photon-forbidden excitons reproduced the temporal and spectral characteristics of both the high-frequency oscillation and low-frequency component. These simulations demonstrated that all responses originated from the quantum interferences of the linear reflection process and nonlinear light-scattering processes owing to the excitonic Floquet states characteristic of 1D Mott insulators. The present results lead to the developments of Floquet engineering, and demonstrate the possibility of rapidly controlling the intensity of visible or near-IR pulse by varying the phase of MIR electric fields, which will be utilized for ultrafast optical switching devices.

Ferroelectrics sometimes show large electro-optical and non-linear optical effects, available for polarization rotation and frequency conversion of light, respectively. If the amplitude of ferroelectric polarization is modulated in the picosecond time domain, terahertz repetition of optical switching via electro-optical and non-linear optical effects would be achieved. Here we show that polarization amplitude can be rapidly modulated by a terahertz electric field in an organic ferroelectric, tetrathiafulvalene- p -chloranil (TTF-CA). In this compound, alternately stacked donor (TTF) and acceptor (CA) molecules are dimerized via the spin-Peierls mechanism, and charge transfer within each dimer results in a new type of ferroelectricity called electronic-type ferroelectricity. Using a terahertz field, the intradimer charge transfer is strongly modulated, producing a subpicosecond change in the macroscopic polarization, which is demonstrated by transient reflectivity and second-harmonic generation measurements. Subsequently, coherent oscillation of the dimeric molecular displacements occur, which is explained by the modulation of the spin moment of each molecule. Controlling ferroelectric polarization on a terahertz timescale is a challenge, because typically the domain-wall motion occurs on much longer time scales. Here, the authors achieve control over the electronic ferroelectricity in an organic material using a terahertz pump–probe technique.

Nearly monocyclic terahertz waves are used for investigating elementary excitations and for controlling electronic states in solids. They are usually generated via second-order optical nonlinearity by injecting a femtosecond laser pulse into a nonlinear optical crystal. In this framework, however, it is difficult to control phase and frequency of terahertz waves. Here, we show that in a one-dimensional Mott insulator of a nickel-bromine chain compound a terahertz wave is generated with high efficiency via strong electron modulations due to quantum interference between odd-parity and even-parity excitons produced by two-color femtosecond pulses. Using this method, one can control all of the phase, frequency, and amplitude of terahertz waves by adjusting the creation-time difference of two excitons with attosecond accuracy. This approach enables to evaluate the phase-relaxation time of excitons under strong electron correlations in Mott insulators. Moreover, phase- and frequency-controlled terahertz pulses are beneficial for coherent electronic-state controls with nearly monocyclic terahertz waves. THz pulses with tuneable properties are desirable for manipulating electronic states in materials. The authors report generation of THz pulses with phase, frequency, and amplitude control by tuning exciton interference in a 1D Mott insulator of transition metal complex and provide insight into exciton dynamics.

Objectives Podoplanin (PDPN) expression in cancer‐associated fibroblasts (CAFs) (CAF‐PDPN) is considered a poor prognostic factor in nonsmall cell lung cancer, but little is known about its clinical significance in high‐grade neuroendocrine carcinoma of the lung (HGNEC). This study examines the association between CAF‐PDPN and stromal programmed death‐ligand 1 (PD‐L1) expression and the prognostic implications of CAF‐PDPN and PD‐L1 expression status in surgically resected HGNEC patients. Methods Immunohistochemical analyses were performed on 121 resected HGNEC specimens using antibodies against PDPN and PD‐L1. Correlations between CAF‐PDPN, stromal PD‐L1 expression, and clinicopathologic features and their implications for survival were analyzed statistically. Results There were substantially more large‐cell neuroendocrine carcinomas in the stromal PD‐L1‐positive group and more vascular invasion in the tumoral PD‐L1‐positive group. PDPN expression in CAF was moderately correlated with stromal PD‐L1 expression (ρ = 0.567, p < 0.001). In a survival analysis combining CAF‐PDPN and stromal PD‐L1 status, the 5‐year RFS rates for Group A: CAF‐PDPN (+)/stromal PD‐L1 (+), Group B: CAF‐PDPN (+)/stromal PD‐L1 (−), Group C: CAF‐PDPN (−)/stromal PD‐L1 (+), and Group D: CAF‐PDPN (−)/stromal PD‐L1 (−) were 62.0%, 46.8%, 17.5%, and 20.2%, respectively, with corresponding 5‐year OS rates of 76.6%, 69.2%, 27.0%, and 25.3%. The log‐rank test showed statistically significant differences among the groups in RFS (p < 0.001) and OS (p < 0.001). Conclusions There is a correlation between CAF‐PDPN and tumoral/stromal PD‐L1 expression, and positive status for either CAF‐PDPN or stromal PD‐L1 expression could be an independent favorable prognostic factor in surgically resected HGNEC patients. We analyzed the correlation between CAF‐PDPN and stromal PD‐L1 expression and their implications for survival in patients with surgically resected high‐grade neuroendocrine carcinoma of the lung (HGNEC). There is a correlation between CAF‐PDPN and tumoral/stromal PD‐L1 expression, and positive status for either CAF‐PDPN or stromal PD‐L1 expression could be an independent favorable prognostic factor in surgically resected HGNEC patients.

Mixed-stack complexes which comprise columns of alternating donors and acceptors are organic conductors with typically poor electrical conductivity because they are either in a neutral or highly ionic state. This indicates that conductive carriers are insufficient or are mainly localized. In this study, mixed-stack complexes that uniquely exist at the neutral–ionic boundary were synthesized by combining donors (bis(3,4-ethylenedichalcogenothiophene)) and acceptors (fluorinated tetracyanoquinodimethanes) with similar energy levels and orbital symmetry between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor. Surprisingly, the orbitals were highly hybridized in the single-crystal complexes, enhancing the room-temperature conductivity (10 −4 –0.1 S cm −1 ) of mixed-stack complexes. Specifically, the maximum conductivity was the highest reported for single-crystal mixed-stack complexes under ambient pressures. The unique electronic structures at the neutral–ionic boundary exhibited structural perturbations between their electron-itinerant and localized states, causing abrupt temperature-dependent changes in their electrical, optical, dielectric, and magnetic properties. Mixed-stack complexes consisting of alternating donors and acceptors typically show low electrical conductivity. Here, the authors improved the conductivity by hybridizing the frontier orbitals of the donor and acceptor at the neutral–ionic boundary.

Two-pore-domain K+ (K2P) channels sense a wide variety of stimuli such as mechanical stress, inhalational anesthetics, and changes in extracellular pH or temperature. The K2P channel activity forms a background K+ current and, thereby, contributes to resting membrane potentials. Six subfamilies including fifteen subtypes of K2P channels have been identified. Each K2P channel molecule with two pores consists of a homodimer of each subtype. In addition, a few heterodimers mainly within the same subfamilies have been found recently. In the present study, the possibility of heterodimerization between TASK1 (TWIK-Related Acid-Sensitive K+ channel) and TALK2 (TWIK-Related Alkaline pH-Activated K+ channel) was examined. These channels belong to separate subfamilies and show extremely different channel properties. Surprisingly, single molecular imaging analyses in this study using a total internal reflection microscope suggested the heterodimerization of TASK1 and TALK2 in a pancreatic cell line, QGP-1. This heterodimer was also detected using a bimolecular fluorescence complementation assay in a HEK293 heterologous expression system. Fluorescence resonance energy transfer analyses showed that the affinity between TASK1 and TALK2 appeared to be close to those of homodimers. Whole-cell patch-clamp recordings revealed that TASK1 currents in HEK293 cells were significantly attenuated by co-expression of a dominant-negative form of TALK2 in comparison with that of wild-type TALK2. The sensitivities of TASK1-TALK2 tandem constructs to extracellular pH and halothane were characterized as a unique hybrid of TASK1 and TALK2. These results suggested that heterodimerization of TASK1 and TALK2 provides cells with the ability to make multiple responses to a variety of physiological and pharmacological stimuli.

PurposeTo investigate the association between nocturia and urinary metabolites in elderly men using metabolomic analysis.MethodsWe recruited 66 men aged 65–80 years. The 3-day frequency volume chart (FCV), International Prostate Symptom Score (IPSS), and quality of life score were used to assess micturition behavior. Participants with the total IPSS > 0 and ≥ 1.5 micturition on an average for three nights were included in the nocturia group. Participants with the total IPSS < 8 and < 1.5 micturition at night were included in the control group. We conducted a comprehensive metabolomic analysis of urine samples. Metabolites were compared between the groups using an unpaired t test. A multivariable logistic regression analysis was used to determine the relationship between nocturia and these metabolites.ResultsThe nocturia and control groups consisted of 45 and 21 men, respectively. There were no differences in the background factors between the groups except for receiving anticholinergic drug and having life style-related diseases. The FVC revealed that nocturnal urine volume, 24 h micturition frequency, and nocturnal micturition frequency were significantly higher in the nocturia group than in the control group. The metabolomic analysis revealed 16 metabolites, which were differentially expressed between the groups. The multivariate analysis showed that increased serotonin level and decreased 3-hydroxypropionic acid and 3-indoleacetonitrile levels were associated with nocturia.ConclusionsThese findings suggest that abnormal urinary metabolites including serotonin, 3-hydroxypropionic acid, and 3-indoleacetonitrile are involved in the pathogenesis of nocturia in elderly men.

Objective The clinical practice of safe and efficient surgery and professional development of general thoracic surgical trainee are both important issues for mentors. We investigated the usefulness of a three-dimensional (3D) endoscopic system application for lung cancer treatment as a tool for training surgical trainees. Methods Supervised by mentors, general thoracic surgical trainees were trained with video-assisted thoracoscopic surgery (VATS) for primary lung cancer using a 3D endoscopic system to enable them to become operators. Video clinics using 3D images were held weekly. The group using 3D endoscopic system (66 cases in the 3D-VATS group) was compared with the group using conventional two-dimensional (2D) thoracoscopic system (35 cases in the 2D-VATS group) to perform VATS lobectomies. Results There was no significant difference in operative time between both groups. However, the 3D-VATS group comprised significantly less experience than the 2D-VATS group. The intraoperative blood loss was significantly reduced for the 3D group (34 mL in the 3D-VATS group vs. 76 mL in the 2D-VATS group, P  = 0.0007). There were no cases of conversion from VATS to open thoracotomy and intraoperative transfusion in either group. Conclusion 3D-VATS and video clinics using 3D videos are useful training tools for general thoracic surgical trainees with little experience in open thoracotomy.

In an electronic system of solids excited by a femtosecond laser pulse, new quantum states called photon-dressed states are created via the coupling of original electron wavefunctions and periodic electric fields of light. The study of photon-dressed states is a central issue in nonlinear optical science, as a coherent response associated with a photon-dressed state can cause ultrafast optical-switching phenomena. In general, however, phase-sensitive dynamics of photon-dressed states are difficult to observe due to their short lifetime. Here, we show that excitation of the organic Mott insulator potassium-tetracyanoquinodimethane with a strong mid-infrared pulse induces a couple of intramolecular vibrations, which add temporally periodic potentials to the electronic system, giving rise to phonon-dressed states in the picosecond time domain. Through sub-cycle spectroscopy using a phase-stable mid-infrared pulse as an excitation and an ultrashort visible pulse as a probe, we observe optical radiation consisting of four kinds of coherent oscillations with double, sum, and differential frequencies of two intramolecular vibrations. The probe-energy dependence of each oscillation can be well interpreted with phonon-dressed states in the framework of Floquet theory. These findings open a possibility for Floquet engineering in correlated electron materials with strong charge–phonon couplings. Floquet engineering describes an approach to tailoring the band structure of a system by applying a time-varying, periodic driving force. Here, the creation of phonon-dressed states following photoexcitation of an organic Mott insulator results in coherent harmonic generation.

High-speed magnetization control of ferromagnetic films using light pulses is attracting considerable attention and is increasingly important for the development of spintronic devices. Irradiation with a nearly monocyclic terahertz pulse, which can induce strong electromagnetic fields in ferromagnetic films within an extremely short time of less than ~1 ps, is promising for damping-free high-speed coherent control of the magnetization. Here, we successfully observe a terahertz response in a ferromagnetic-semiconductor thin film. In addition, we find that a similar terahertz response is observed even in a non-magnetic semiconductor and reveal that the electric-field component of the terahertz pulse plays a crucial role in the magnetization response through the spin-carrier interactions in a ferromagnetic-semiconductor thin film. Our findings will provide new guidelines for designing materials suitable for ultrafast magnetization reversal.