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.

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.

[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.

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.

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.

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.

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.

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.

Dorsomorphin stimulates neurite outgrowth in PC12 cells via activation of a protein kinase A-dependent MEK-ERK1/2 signaling pathway.

In this study, we investigated the effect of dorsomorphin, a selective inhibitor of bone morphogenetic protein (BMP) signaling, on rat PC12 pheochromocytoma cell differentiation. PC12 cells can be induced to differentiate into neuron-like cells possessing elongated neurites by nerve growth factor, BMP2, and other inducers. Cells were incubated with BMP2 and/or dorsomorphin, and the extent of neurite outgrowth was evaluated. Unexpectedly, BMP2-mediated neuritogenesis was not inhibited by co-treatment with dorsomorphin. We also found that treatment with dorsomorphin alone, but not another BMP signaling inhibitor, LDN-193189, induced neurite outgrowth in PC12 cells. To further understand the mechanism of action of dorsomorphin, the effects of this drug on intracellular signaling were investigated using the following signaling inhibitors: the ERK kinase (MEK) inhibitor U0126; the tropomyosin-related kinase A inhibitor GW441756; and the protein kinase A (PKA) inhibitor H89. Dorsomorphin induced rapid and sustained ERK1/2 activation; however, dorsomorphin-mediated ERK1/2 activation and neuritogenesis were robustly inhibited in the presence of U0126 or H89, but not GW441756. These findings suggest that dorsomorphin has the potential to induce neuritogenesis in PC12 cells, a response that requires the activation of PKA-dependent MEK-ERK1/2 signaling.

Ab initio simulation of helium-ion microscopy images: the case of suspended graphene.

Helium ion microscopy (HIM), which was released in 2006 by Ward et al., provides nondestructive imaging of nanoscale objects with higher contrast than scanning electron microscopy. HIM measurement of suspended graphene under typical conditions is simulated by first-principles time-dependent density functional theory and the 30 keV He+ collision is found to induce the emission of electrons dependent on the impact point. This finding suggests the possibility of obtaining a highly accurate image of the honeycomb pattern of suspended graphene by HIM. Comparison with a simulation of He0 under the same kinetic energy shows that electron emission is governed by the impact ionization instead of Auger process initiated by neutralization of He+.

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.

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.

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.

Photoexfoliation of graphene from graphite: an ab initio study.

We propose to use ultrashort laser pulses to detach intact graphene monolayers from a graphite surface, one at a time. As suggested by a combination of real-time ab initio time-dependent density functional calculations for electrons with molecular dynamics simulations for ions, this athermal exfoliation process follows exposure to femtosecond laser pulses with a wavelength of 800 nm and the full width at half maximum (FWHM) of 45 fs. Shorter pulses (FWHM=10 fs) with the same wavelength and intensity speed up the exfoliation and cause transient contraction in subsurface layers. Photoexfoliation should be capable of producing intact graphene monolayers free of contaminants and defects at a high rate.

First-principles simulations of chemical reactions in an HCl molecule embedded inside a C or BN nanotube induced by ultrafast laser pulses.

We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

Simulated ultra-fast phenomena in photo-excited carbon nanotube.

Ab-initio simulations to explore photo-induced dynamics in nanotubes are presented. By using the time-dependent density functional theory, simulations of electron-ion dynamics in nanotubes were performed with aid of supercomputers. From the simulation results, efficient methods of detection of structural defects and elimination of oxygen impurities from nanotubes are proposed. Furthermore, hot-carrier decay process and modulation of optical field in nanotubes are analyzed. In this review, the computational scheme and the simulation results are introduced.

Excited state carbene formation from UV irradiated diazomethane.

The laser flash photolysis process of diazomethane has been studied by using a real time propagation time-dependent density functional theory (RTP-TDDFT) combined with molecular dynamics. The activation energy barrier for disintegrating diazomethane into nitrogen (N(2)) and carbene (CH(2)) molecules significantly decreases in the electronic excited S(1) state compared to that in the S(0) ground state. Furthermore, the produced carbene molecule can be in the electronic excited state of (1)CH(2) ((1)B(1)) instead of the lowest state among singlet states (1)CH(2) ((1)A(1)), which is evident in the wave function characteristics of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) throughout the disintegration. This is regarded as the initial stage of the rearrangement in the excited state (RIES), the evidence of which has been given by experiments in the past decade. In the RIES mechanism scheme, we suggest that the photoreaction in the S(1) state contributes considerably to the photochemistry of carbene formation. The passing near the S(1)/S(0) conical intersection, which allows the transition to ground state diazomethane producing the lowest singlet state carbene molecule, is considered a rare event from our molecular dynamics, although this has been regarded as the dominant mechanism in previous theoretical studies.

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.