Polarization Dependence of Laser-Induced Dynamics on Non-Flat Metal Surfaces: A Time-Dependent Density Functional Theory Approach.

Real-time time-dependent density functional theory was used to study the laser-pulse-induced ion dynamics on metal surfaces featuring rows of atomic ridges. In contrast to atomically flat surfaces, the rows of atomic ridges induce anisotropy on the surface even in surface-parallel directions. This anisotropy causes the laser-induced ion dynamics to depend on the orientation of the laser polarization vector in the surface-parallel directions. This polarization dependence occurs for both copper (111) and aluminum (111) surfaces, indicating that the existence of localized d orbitals in the electronic system does not play a crucial role. The difference in kinetic energies between ions on the ridges and those on the planar surface reached a maximum when the laser polarization vector was perpendicular to the rows of ridges but parallel to the surface. A simple mechanism for the polarization dependence and some potential applications in laser processing are discussed.

First-Principles Study of the Optical Dipole Trap for Two-Dimensional Excitons in Graphane.

Recent studies on excitons in two-dimensional materials have been widely conducted for their potential usages for novel electronic and optical devices. Especially, sophisticated manipulation techniques of quantum degrees of freedom of excitons are in demand. In this Letter we propose a technique of forming an optical dipole trap for excitons in graphane, a two-dimensional wide gap semiconductor, based on first-principles calculations. We develop a first-principles method to evaluate the transition dipole matrix between excitonic states and combine it with the density functional theory and GW+BSE calculations. We reveal that in graphane the huge exciton binding energy and the large dipole moments of Wannier-like excitons enable us to induce the dipole trap of the order of meV depth and µm width. This Letter opens a new way to control light-exciton interacting systems based on newly developed numerically robust ab initio calculations.

M1-like macrophage contributes to chondrogenesis in vitro.

Cartilage tissues have poor self-repairing abilities. Regenerative medicine can be applied to recover cartilage tissue damage in the oral and maxillofacial regions. However, hitherto it has not been possible to predict the maturity of the tissue construction after transplantation or to prepare mature cartilage tissues before transplantation that can meet clinical needs. Macrophages play an important role in cartilage tissue regeneration, although the exact mechanisms remain unknown. In this study, we established and verified an in vitro experimental system for the direct co-culture of cell pellets prepared from mouse auricular chondrocytes and macrophages polarized into four phenotypes (M1-like, M1, M2-like, and M2). We demonstrate that cartilage pellets co-cultured with M1-like promoted collagen type 2 and aggrecan production and induced the most significant increase in chondrogenesis. Furthermore, M1-like shifted to M2 on day 7 of co-culture, suggesting that the cartilage pellet supplied factors that changed the polarization of M1-like. Our findings suggest that cartilage regenerative medicine will be most effective if the maturation of cartilage tissues is induced in vitro by co-culture with M1-like before transplantation.

Direct treatment of interaction between laser-field and electrons for simulating laser processing of metals.

Laser ablation is often simulated by the two-temperature model in which electrons are assumed to be thermalized by laser irradiation, while an explicit representation of interaction between laser-field and electrons is challenging but beneficial as being free from any adjustable parameters. Here, an ab initio method based on the time-dependent density functional theory (TDDFT) in which electron-ion dynamics under a laser field are numerically simulated is examined as a tool for simulating femtosecond laser processing of metals. Laser-induced volume expansion in surface normal directions of Cu(111) and Ni(111) surfaces are simulated by using repeating slab models. The amount of simulated volume expansion is compared between Cu(111) and Ni(111) slabs for the same laser pulse conditions, and the Ni slab is found to expand more than the Cu slab despite the smaller thermal expansion coefficient of Ni compared with Cu. The analyzed electronic excitation and lattice motion were compared to those in the two-temperature model. The threshold fluence to release surface Cu atom deduced from current TDDFT approach is found to be comparable to those of Cu ablation reported experimentally.

A Rare Case of Chronic Expanding Intrapericardial Hematoma with Refractory Right-sided Heart Failure 30 Years after the Surgical Repair of Tetralogy of Fallot.

We herein report the case of a 79-year-old man who presented with right-sided heart failure (HF) 27 years after undergoing surgery for tetralogy of Fallot. The HF did not respond well to oral diuretics. Transthoracic echocardiography and chest X-ray failed to determine the cause of the HF for three years. An intrapericardial mass located just behind the sternum, was finally identified on computed tomography. The mass had compressed the right ventricle, causing right-sided HF. Pre-surgical diagnostic images led to suspicion of a chronic expanding intrapericardial hematoma (CEIH), and the CEIH was surgically removed. The patient's symptoms improved markedly.

Selecting Carbon Nanotubes with Diameters of Less than 1 nm by Laser Pulses: An Ab Initio Exploration.

Despite the thermal instability of carbon nanotubes (CNTs) with diameters of less than 1 nm, first-principles simulations indicate the possibility of selecting such narrow CNTs using laser pulses. The simulations suggested the possibility of selecting CNTs narrower than 1 nm under pulsed laser irradiation with a full width at half-maximum of 10 fs, a wavelength of 800 nm, and a maximum field intensity ranging from 4.5 to 5 V/Å when the polarization vector was set perpendicular to the CNT axis. This result was common to both zigzag and armchair CNTs, suggesting that the preferential survival of narrow CNTs is independent of the chirality. The mechanisms underlying the preferential survival of narrower CNTs are discussed from analogous simulations of graphene nanoribbons under various polarization directions of the laser field, and the possibility of selecting CNTs with subnanometer diameters is evaluated on the basis of the simulation results.

[Acquired factor V inhibitor associated with apixaban].

Acquired factor V inhibitor is an acquired coagulation disorder that is rare. We report the case of a patient who was treated with apixaban and developed acquired factor V inhibitor. The patient was a 76-year-old man who has been on long-term treatment with aspirin and clopidogrel after undergoing percutaneous coronary intervention (PCI) and carotid artery stenting. In June, he developed a cerebral infarction six days after the second PCI. Apixaban was added to his treatment regimen for cariogenic cerebral embolism. Three months later, intramuscular hemorrhage occurred in his left leg after a fall. However, the hemorrhage improved upon aspirin withdrawal. Unexpectedly, subcutaneous and intramuscular hemorrhage recurred three months after the patient commenced anticoagulation therapy. At this time, the APTT was 242.5 seconds and the PT was over the reference range. Although clopidogrel and apixaban were discontinued, these abnormalities did not improve. However, a cross-mixing test showed an inhibitor pattern, with factor V activity being less than 1% and its inhibitor level being 8.0 BU/ml. Based on these findings, the patient was finally diagnosed of acquired factor V inhibitor. One month after prednisolone administration at 20 mg/day, the PT and APTT were normalized, and prednisolone was tapered off. Although the use of dabigatran has been associated with iatrogenic acquired factor V inhibitor, we describe the first case of acquired factor V inhibitor associated with direct Xa inhibitor.

Molecular-scale modeling of light emission by combustion: An ab initio study.

Despite the advanced understanding of combustion, the mechanisms of subsequent light emission have not attracted much attention. In this work, we model the light emission as electronic excitation throughout the oxidation reaction. We examined the simple dynamics of the collision of an oxygen molecule (O2) with a kinetic energy of 4, 6, or 10 eV with a stationary target molecule (Mg2, SiH4 or CH4). Time-dependent density functional theory was used to monitor electronic excitation. For a collision between O2 and Mg2, the electronic excitation energy increased with the incident kinetic energy. In contrast, for a collision between O2 and SiH4 molecules, a substantial electronic excitation occurred only at an incident kinetic energy of 10 eV. The electronic excitation was qualitatively reproduced by analysis using complete active space self-consistent field method. On the other hand, collision between O2 and CH4 molecules shows reflection of these molecules indicating that small-mass molecules could show neither oxidation nor subsequent electronic excitation upon collision with an O2 molecule. We believe that this work provides a first step toward understanding the light-emission process during combustion.

[Refractory Hypertension and Intermittent Claudication Caused by Distal Elephant Trunk Stenosis 10 Years After Total Arch Replacement for Stanford Type A Aortic Dissection;Report of a Case].

A 49-year-old man was admitted to our hospital because of intermittent claudication and refractory hypertension 10 years after surgery to Stanford type A acute aortic dissection. He underwent total arch replacement with an elephant trunk of 22 mm in diameter. Transesophageal echocardiography revealed that distal end of the elephant trunk was stenosed. Systolic blood pressure gradient over this portion reached to more than 100 mmHg. Folding of elephant trunk and thrombus formation were considered to be the cause. Thoracic endovascular aortic repair relieved stenosis and intermittent claudication, and enabled better blood pressure control.

Investigating the Efficacy of Intraoral Wet Sheets.

OBJECTIVE: It is important that oral care is effective, efficient, and economical. Herein, we investigated the efficacy of intraoral wet sheets for oral care in comparison with sponge brushes. METHODS: We completed a Plaque Control Record (PCR) after observing intraoral plaque using a plaque disclosure test in healthy volunteers. After the teeth were cleaned for 3 minutes using a wet sheet, the test was repeated and the PCR was completed. The same method was performed using a sponge brush on the same subject under the same conditions 1 week later. The t test was used to analyze PCR findings. RESULTS: Ten healthy subjects were enrolled (mean age, 28.6 years). The PCR values improved from 44.0% before to 30.9% after use of the wet sheet. The post-cleaning PCR was significantly lower. The PCR values improved from 55.0% before to 50.2% after use of the sponge brush. CONCLUSIONS: The PCR improvement was greater when using the wet sheet. In all cases, the wet sheet was highly effective at smoothing tooth surfaces. Intraoral wet sheets may be an option for oral care performed by nurses and caregivers. Compared to the sponge brush, the intraoral wet sheet can save time and reduce costs.

Tin-Vacancy Quantum Emitters in Diamond.

Tin-vacancy (Sn-V) color centers were created in diamond via ion implantation and subsequent high-temperature annealing up to 2100 °C at 7.7 GPa. The first-principles calculation suggested that a large atom of tin can be incorporated into a diamond lattice with a split-vacancy configuration, in which a tin atom sits on an interstitial site with two neighboring vacancies. The Sn-V center showed a sharp zero phonon line at 619 nm at room temperature. This line split into four peaks at cryogenic temperatures, with a larger ground state splitting (∼850 GHz) than that of color centers based on other group-IV elements, i.e., silicon-vacancy (Si-V) and germanium-vacancy (Ge-V) centers. The excited state lifetime was estimated, via Hanbury Brown-Twiss interferometry measurements on single Sn-V quantum emitters, to be ∼5 ns. The order of the experimentally obtained optical transition energies, compared with those of Si-V and Ge-V centers, was in good agreement with the theoretical calculations.

Conservation of the pure adiabatic state in Ehrenfest dynamics of the photoisomerization of molecules.

We examined real-time-propagation time-dependent density functional theory (rtp-TDDFT) coupled with molecular dynamics (MD), which uses single-particle representation of time-evolving wavefunctions allowing exchange of orbital characteristics between occupied and empty states making the effective Kohn-Sham Hamiltonian dependent on the potential energy surfaces (PESs). This scheme is expected to lead to mean-field average of adiabatic potential energy surfaces (PESs), and is one of Ehrenfest (mean-field) approaches. However, we demonstrate that the mean-field average can be absent in simulating photoisomerization of azobenzene and ethylene molecules. A transition from the S2 to the S1 excited state without the mean- field average was observed after examining several rtp-TDDFT-MD trajectories of a photoexcited azobenzene molecule. The subsequent trans-cis isomerization was observed in our simulation, which is consistent with experimental observation and supported by previous calculations. The absence of the mean-field average of PESs was also observed for the transition between the S1 and S0 states, indicating that the MD simulation was on a single PES. Conversely, we found no transition to the ground state (S0 state) when we performed a MD simulation of an S1 excited ethylene molecule owing to the constraint on the occupation number of each molecular orbital. Thus, we conclude that, at least for azobenzene and ethylene molecules, the rtp-TDDFT-MD is an on-the-fly simulation that can automatically see the transition among the PESs of excited states without the mean-field average unless the simulation reaches the PES of the S0 state.

Optical field terahertz amplitude modulation by graphene nanoribbons.

In this study, first-principles time-dependent density functional theory calculations were used to demonstrate the possibility to modulate the amplitude of the optical electric field (E-field) near a semiconducting graphene nanoribbon. A significant enhancement of the optical E-field was observed 3.34 Å above the graphene nanoribbon sheet, with an amplitude modulation of approximately 100 fs, which corresponds to a frequency of 10 THz. In general, a six-fold E-field enhancement could be obtained, which means that the power of the obtained THz is about 36 times that of incident UV light. We suggest the use of semiconducting graphene nanoribbons for converting visible and UV light into a THz signal.

Germanium-Vacancy Single Color Centers in Diamond.

Atomic-sized fluorescent defects in diamond are widely recognized as a promising solid state platform for quantum cryptography and quantum information processing. For these applications, single photon sources with a high intensity and reproducible fabrication methods are required. In this study, we report a novel color center in diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV center, which has a sharp and strong photoluminescence band with a zero-phonon line at 602 nm at room temperature. We demonstrate this new color center works as a single photon source. Both ion implantation and chemical vapor deposition techniques enabled fabrication of GeV centers in diamond. A first-principles calculation revealed the atomic crystal structure and energy levels of the GeV center.

Modifying the interlayer interaction in layered materials with an intense IR laser.

We propose a transient interlayer compression in two-dimensional compound materials by using an intense IR laser resonant with the out-of-plane optical phonon mode (A(2u) mode). As a test case, we studied bilayer hexagonal boron nitride (h-BN), which is one of the compound layered materials. Excited state molecular dynamics calculations using time-dependent density functional theory show an 11.3% transient interlayer contraction of h-BN due to an interlayer dipole-dipole attraction of the laser-pumped A(2u) mode. These results are applicable to other layered compound materials. Such layered materials are a good material for nanospace chemistry, e.g., intercalating molecules and acting with them, and IR irradiation to contract the interlayer distance could provide a new route for chemical reactions under pressure. The duration of the contraction is at least 1 ps in the current simulation, which is observable by high-speed electron-beam diffraction measurements.

New Li-doped fullerene-intercalated phthalocyanine covalent organic frameworks designed for hydrogen storage.

Applying density functional theory (DFT) calculations, we have designed fullerenes (C20, C24, C26, C28, C30, C36, C60 and C70) intercalated phthalocyanine covalent organic frameworks (Cn-Pc-PBBA COFs). First principles molecular dynamics (MD) simulations showed that the structures of Cn-Pc-PBBA COFs are stable at room temperature and even at higher temperature (500 K). The interlayer distance of Pc-PBBA COF has been expanded to 7.48-13.25 Å by the intercalated fullerenes, and the pore volume and surface area were enlarged by 2.3-3.1 and 2.0-2.6 times, respectively. The grand canonical Monte Carlo (GCMC) simulations show that our designed Cn-Pc-PBBA COFs exhibit a superior hydrogen storage capability: at 77 K and P = 100 bar, the hydrogen gravimetric and volumetric uptakes reach 9.4-12 wt% and 48.1-52.2 g L(-1), respectively. To meet the requirement for practical application in hydrogen storage, we use the Li-doping method to modify the hydrogen storage performance of Cn-Pc-PBBA COFs. Our results show that the Li atoms can stably locate on the surface of C30-, C36, C60 and C70-Pc-PBBA COFs. At T = 298 K and P = 100 bar, for these four Li-doped Cn-Pc-PBBA COFs, the gravimetric and volumetric uptakes of H2 reach 4.2 wt% and 18.2 g L(-1), respectively.

Highly responsive ultrathin GaS nanosheet photodetectors on rigid and flexible substrates.

The first GaS nanosheet-based photodetectors are demonstrated on both mechanically rigid and flexible substrates. Highly crystalline, exfoliated GaS nanosheets are promising for optoelectronics due to strong absorption in the UV-visible wavelength region. Photocurrent measurements of GaS nanosheet photodetectors made on SiO2/Si substrates and flexible polyethylene terephthalate (PET) substrates exhibit a photoresponsivity at 254 nm up to 4.2 AW(-1) and 19.2 AW(-1), respectively, which exceeds that of graphene, MoS2, or other 2D material-based devices. Additionally, the linear dynamic range of the devices on SiO2/Si and PET substrates are 97.7 dB and 78.73 dB, respectively. Both surpass that of currently exploited InGaAs photodetectors (66 dB). Theoretical modeling of the electronic structures indicates that the reduction of the effective mass at the valence band maximum (VBM) with decreasing sheet thickness enhances the carrier mobility of the GaS nanosheets, contributing to the high photocurrents. Double-peak VBMs are theoretically predicted for ultrathin GaS nanosheets (thickness less than five monolayers), which is found to promote photon absorption. These theoretical and experimental results show that GaS nanosheets are promising materials for high-performance photodetectors on both conventional silicon and flexible substrates.

Pulse-induced nonequilibrium dynamics of acetylene inside carbon nanotube studied by an ab initio approach.

Nanoscale molecular confinement substantially modifies the functionality and electronic properties of encapsulated molecules. Many works have approached this problem from the perspective of quantifying ground-state molecular changes, but little is known about the nonequilibrium dynamics of encapsulated molecular system. In this letter, we report an analysis of the nonequilibrium dynamics of acetylene (C(2)H(2)) inside a semiconducting carbon nanotube (CNT). An ultrashort high-intense laser pulse (2 fs width and 10(15) W/cm(2) intensity) brings the systems out of equilibrium. This process is modeled by comprehensive first-principles time-dependent density-functional simulations. When encapsulated, acetylene dimer, unlike a single acetylene molecule, exhibits correlated vibrational dynamics (C-C bond rotation and H-C-C bending) that is markedly different from the dynamics observed in the gas phase. This result highlights the role of CNT in modulating the optical electric field within the tube. At longer simulation timescales (> 20 fs) in the largest-diameter tube studied here [CNT(14,0)], we observe synchronized rotation about the C-C axes in the dimer and ultimately ejection of one of the four hydrogen atoms. Our results illustrate the richness of photochemical phenomena in confined geometries.