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High-entropy materials have attracted considerable interest due to their unique, improved properties and large configurational entropy. Out of these, high-entropy ceramics (HECs) are of particular interest since the independent solubility of cations and anions results in increased configurational entropy. However, most HEC research considers only a single element occupying the anion sublattice, which limits the maximum attainable configurational entropy. Here, we expand our previous work on high-entropy borocarbides where both boron and carbon occupy the anion sublattice. By applying an ab initio based screening procedure, we identify six elements Li, Ti, V, Zr, Nb and Hf suitable for forming high-entropy borocarbides. With these elements, we propose six novel HEC compositions, and by computing their entropy forming ability, we identify that three are likely to form single-phase during synthesis. Material properties and lattice distortions for all proposed compositions are studied using density functional theory calculations with special quasirandom structures. The directional lattice distortions, a concept we introduce in this work, show that lattice distortions have an elemental and directional preference for certain HEC compositions. We also show that the novel inclusion of Li improves the mechanical properties of the proposed HECs, the details of which are studied using the electron localization function.

It is well known that the laser-induced dynamics of a system is determined by three laser parameters, namely, wavelength, pulse width, and intensity. In this study, the laser polarization is presented as a new parameter that determines the dynamics of highly anisotropic materials. By performing first-principles electron-ion dynamics simulations assuming a laser wavelength of 800 nm, a full width at half-maximum of 10 fs, and a field intensity of 4 V/A, carbon nanotubes (CNTs) were found to be fragile or robust when the polarization was parallel or perpendicular, respectively, to the tube axis. This behavior was observed for both zigzag and armchair CNTs and is thus expected to be only weakly dependent on CNT chirality. The obtained results are anticipated to encourage experimental efforts to select CNTs of a particular orientation using pulsed lasers with controlled polarization.

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.

We report the optical observation of lead-vacancy (PbV) centers in diamond fabricated by Pb ion implantation and subsequent high-temperature annealing (2100 {\deg}C) under high pressure (7.7 GPa). Their optical properties were characterized by photoluminescence at varying temperatures down to 5.7 K. We observed intense emission peaks at 550 and 554 nm with a large splitting of approximately 3900 GHz. The two lines are thought to correspond to the zero phonon line (ZPL) of PbV centers with split ground and excited states. A cubic trend of the ZPL width was observed while varying temperature. We performed polarization measurements of the two lines in a single PbV center, showing nearly orthogonal dipole polarizations. These optical measurements strongly indicate that the PbV center possesses D3d symmetry in the diamond lattice. The observed large ground state splitting significantly suppresses the phonon-mediated transition, which causes decoherence of the electron spin state of the group IV color centers in diamond, expecting a long spin coherence time at a temperature of approximately 8 K.

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.

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.

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.

Recently, all-inorganic perovskite quantum dots have become a hot research topic due to their unique optical response. We have studied barium titanate quantum dots and their hybrid structure consis...

Twin graphene is a new two-dimensional semiconducting carbon allotrope which is proposed recently. The structural, magnetic and electronic properties are investigated for 3d transition metal (TM) atom adsorbed twin graphene by means of GGA+U calculations. The results show most of single 3d transition metal atom except Zn can make twin graphene magnetization. The adsorption of single TM atom can also make the twin graphene systems turn to half metal (V adsorption), half-semiconductor (Fe adsorption) or metal (Sc, Cr, Mn, Co and Cu adsorption). The semiconducting nature still exists for Ti, Ni and Zn adsorption. All the 3d TM adatoms belong to n-type doping for transferring charge to the neighboring C atoms and have strong covalent bond with these C atoms. The influence of Hubbard U value on half-metallic V adsorbed system is also considered. As the U increases, the system can gradually transform from metal to half metal and metal. The effect of the coverage is investigated for two TM atoms (Sc-Fe) adsorption, too. We can know TM atoms adsorbed twin graphene have potentials to be spintronic device and nanomagnets from the results.

Optical properties of oxidized single-wall carbon nanotubes (SWCNTs) have attracted much attention because of the greater luminescence quantum yield than that of pristine CNTs, showing the possibility of optical applications such as near-infrared single-photon emitters and bioimaging. To advance the fundamental understanding of the optical properties, we theoretically investigated the energetics and the optical transitions for complex oxygen (O) adsorption structures on (6,5) CNTs, including adsorption of two O atoms. For CNTs adsorbed by isolated O atoms, four groups of optical transition levels were obtained below E 11 . We also found two additional groups of optical transition levels for adsorption structures of two O atoms, whose related adsorption structures are more stable than the isolated O-adsorption structures. These results explain the multiple emission peaks and their irradiation time dependence in the photoluminescence (PL) spectra for CNTs oxidized by ultraviolet ozone, providing a possible mechanism for significant brightening of the emission whose wavelength range is ideal for biological imaging. Our results are also consistent with the PL measurements of SWCNTs oxidized by O 2 molecules during single chirality separation processes. This comprehensive understanding is essential for further applications of oxidized SWCNTs.

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.

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.

First-principles simulations were used to investigate water (H2O) decomposition induced by a femtosecond laser with high flux ∼1 × 1020 photons/(sec cm2 ). One goal of our research is to find metamaterials that locally enhance the laser field to reduce the threshold laser intensity required to decompose H2O molecules. In this work, small-diameter (6.3 Å) single-walled carbon nanotubes were found to reduce the threshold power by 90% compared with the power required to decompose H2O in the gas phase. The present results suggest a strategy for the design of materials with high energy efficiency for H2O decomposition based on polarizability and morphology (curvature) to enhance the local field. We demonstrate that carbon nanotubes enhance the local field resulting in a power enhancement of approximately eight times., X.C. acknowledges financial support from the National Natural Science Foundation of China (Grant No. 11774248). A.R. acknowledges financial support from the JSPS Fellowship program, the European Research Council (Grant No. QSpec-NewMat ERC-2015-AdG-694097), and Grupos Consolidados (Grant No. IT578-13).

Recent advances in ultrashort laser pulse techniques have opened up a wide variety of applications in both fundamental physics and industrial fields. In this work, $ab\phantom{\rule{4pt}{0ex}}initio$ molecular dynamics simulations based on time-dependent density functional theory revealed a steady deceleration of lattice distortion propagation in an aluminum slab with increasing laser pulse intensity. Analyzing the interatomic force revealed a significant reduction in the harmonic terms and nonmonotonic growth of anharmonicity. This is characterized by spatially nonuniform force screening by plasmon under a nonperturbative excitation condition that is not captured in Born--Oppenheimer molecular dynamics, and is consistent with the current interpretation of laser-induced periodic structure patterning. This work highlights the significance of collective electronic excitations for modeling the structure formation in such a system.

Using time-dependent density function theory (TDDFT), we have carried out a systematic study of collective excitations of the AB-stacked and AA-stacked few-layer graphene nanostructures with rectangle geometries. We found little effect of stacking sequence on the excitation properties of few-layer graphene nanostructures when the polarized direction of impulse excitation is in the armchair-edge or in the zigzag-edge directions. However, the effect of the stacking sequence becomes significant when the polarized direction was perpendicular to the layers. The absorption strength in the bilayer/trilayer system is slightly more than twice/three times as strong as that in the monolayer system. With the increase of the number of the layers, in the lower-energy resonance zone, absorption spectra are blue-shifted. The increasing strength of the optical absorption has also been found when the interlayer distance is increased followed by red shift in the supreme absorption peak. We found high energy resonances of πplasmons at 4–8 eV are localized in the boundary region showing dipole-like character. The current findings may pave a way for the potential applications in UV regions if there are available nanomechanical devices to tune stacking and interlayer distance.

First-principles calculations of electron-ion dynamics based on real-time time-dependent density functional theory were performed to study the lattice dynamics in yttrium aluminum garnet (YAG) doped with cerium (Ce) following photoexcitation. The dynamics induced by the optical transitions from the valence band to the conduction band of the YAG host and from the Ce 4f to 5 d levels were examined. Significant lattice motion was observed in the latter case. This lattice motion (Franck-Condon relaxation) decreased the Ce–O bond length by 0.05 A and increased the energy of the Ce 4f level by 0.5 eV, suggesting a Stokes shift in the light emission due to the Ce 5 d→4f transition. The calculated Stokes shift is consistent with the recently reported experimental value, despite the approximations used in the present calculations. The effect of lattice temperature was also examined up to 300 K.

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.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.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.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.

This paper describes the application of time-dependent density functional theory (TDDFT) to explore dynamics in condensed matter driven by strong short laser pulses. As a specific example, the calculation of the optical response on a gold surface is presented. The real-time TDDFT treatment of metallic systems is difficult due to the presence of a surface of the Fermi level (EF). Depending on EF, the occupation numbers of the states at each of the k points in the wedge of the first Brillouin zone should be assigned to obtain self-consistent charge-density and Kohn–Sham wavefunctions, which are set as the initial condition for the real-time propagation based on TDDFT. Furthermore, a computational scheme for exploring the optical field enhancement by the Au surface and numerical problems arising from the periodic boundary conditions are discussed.

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., HZ and XLC acknowledge financial support from the National Natural Science Foundation of China (Grant No. 11474207 and Grant No. 11374217). YM acknowledges the fund from MEXT, Grant-in-Aid for Scientific Research on Innovative Areas “Science of Atomic Layers (SATL)”, Japan, and the support from Research organization of Information Science and Technology (RIST) at Tokyo. AR acknowledges financial support from the European Research Council Advanced Grant DYNamo (ERC-2010-AdG-267374), Spanish Grant (FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13) and COST Actions CM1204 (XLIC) and MP1306 (EUSpec).

Tin-vacancy (SnV) color centers were created in diamond by ion implantation and subsequent high temperature annealing up to 2100 {\deg}C at 7.7 GPa. The first-principles calculation suggests that the large atom of tin can be incorporated into the diamond lattice with a split-vacancy configuration, in which a tin atom sits on an interstitial site with two neighboring vacancies. The SnV center shows a sharp zero phonon line at 619 nm at room temperature. This line splits into four peaks at cryogenic temperatures with a larger ground state splitting of ~850 GHz than those of color centers based on other IV group elements, silicon-vacancy (SiV) and germanium vacancy (GeV) centers. The excited state lifetime was estimated to be ~5 ns by Hanbury Brown-Twiss interferometry measurements on single SnV quantum emitters. The order of the experimentally obtained optical transition energies comparing with the SiV and GeV centers is good agreement with the theoretical calculations., Comment: 10 pages, 4 figures and Supplementary 3 pages, 2 figures

Recently, single-layer group III monochalcogenides have attracted both theoretical and experimental interest at their potential applications in photonic devices, electronic devices, and solar energy conversion. Excited by this, we theoretically design two kinds of highly stable single-layer group IV-V ($\mathrm{IV}=\mathrm{Si},\mathrm{Ge}$, and Sn; $\mathrm{V}=\mathrm{N}$ and P) and group V-IV-III-VI ($\mathrm{IV}=\mathrm{Si},\mathrm{Ge}$, and Sn; $\mathrm{V}=\mathrm{N}$ and P; $\mathrm{III}=\mathrm{Al},\mathrm{Ga}$, and In; $\mathrm{VI}=\mathrm{O}$ and S) compounds with the same structures with single-layer group III monochalcogenides via first-principles simulations. By using accurate hybrid functional and quasiparticle methods, we show the single-layer group IV-V and group V-IV-III-VI are indirect bandgap semiconductors with their bandgaps and band edge positions conforming to the criteria of photocatalysts for water splitting. By applying a biaxial strain on single-layer group IV-V, single-layer group IV nitrides show a potential on mechanical sensors due to their bandgaps showing an almost linear response for strain. Furthermore, our calculations show that both single-layer group IV-V and group V-IV-III-VI have absorption from the visible light region to far-ultraviolet region, especially for single-layer SiN-AlO and SnN-InO, which have strong absorption in the visible light region, resulting in excellent potential for solar energy conversion and visible light photocatalytic water splitting. Our research provides valuable insight for finding more potential functional two-dimensional semiconductors applied in optoelectronics, solar energy conversion, and photocatalytic water splitting.

Through first-principles investigation, we display the formation process of Shockley-type surface states which emerges on silver thin films along Ag (1 1 1) orientation with increasing thicknesses from 6 to 21 layers. We look at the surface state band for various adatoms adsorbed on 6, 12, 18 layers strained Ag (1 1 1) films with different coverage, and discuss the long range interaction mediated by surface state electrons. We discovered that film's thickness can modulate the surface state mediated interaction drastically, but the dipole–dipole repulsive interaction is not affected by slab thickness. This factor had never been discussed in detail. Therefore, adatoms adsorbed on thin films have strong attractive interaction which leads to small adsorption separation and the tendency of island formation. For different coverage or different adsorbate types, both surface states and dipole moment are modulated. The three factors, film's thickness, adsorbate coverage and adatoms types, could help us learn more about the interactions between adatoms and exploit advanced ways to control surface geometry structures of self-assembly.

A novel type of three-dimensional (3D) tetrahedral silsesquioxane-based porous frameworks (TSFs) with diamond-like structure was computationally designed using the density functional theory (DFT) and classical molecular mechanics (MM) calculations. The hydrogen adsorption and diffusion properties of these TSFs were evaluated by the methods of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results reveal that all designed materials possess extremely high porosity (87–93 %) and large H2 accessible surface areas (5,268–6,544 m2 g−1). Impressively, the GCMC simulation results demonstrate that at 77 K and 100 bar, TSF-2 has the highest gravimetric H2 capacity of 29.80 wt%, while TSF-1 has the highest volumetric H2 uptake of 65.32 g L−1. At the same time, the gravimetric H2 uptake of TSF-2 can reach up to 4.28 wt% at the room temperature. The extraordinary performances of these TSF materials in hydrogen storage made them enter the rank of the top hydrogen storage materials so far.

We use time-dependent density functional theory to study laser-pulse induced decomposition of H2O molecules above the two-dimensional (2D) materials graphene, hexagonal boron nitride, and graphitic carbon nitride. We examine femtosecond-laser pulses with a full width at half maximum of 10 or 20 fs for laser-field intensity and wavelengths of 800 or 400 nm by varying the intensity of the laser field from 5 to 9 V/Å, with the corresponding range of fluence per pulse up to 10.7J/cm2. For a H2O molecule above the graphitic sheets, the threshold for laser-field H2O decomposition is reduced by more than 20% compared with that of an isolated H2O molecule. We also show that hole doping enhances the water adsorption energy above graphene. The present results indicate that the graphitic materials should support laser-induced chemistry and that other 2D materials that can enhance laser-induced H2O decomposition should be investigated., Y.M. acknowledges funding from JSPS KAKENHI Grants No. JP16H00925, No. JP16H04103, and No. JP16K05049. Y.M. also acknowledges support from the Research Organization of Information Science and Technology (RIST), Tokyo. H.Z. and X.C. acknowledge financial support from the National Key R&D Program of China 2017YFA0303603 and the National Natural Science Foundation of China (Grants No. 11474207 and No. 11374217). A.R. acknowledges financial support from the JSPS Fellowship program and from the European Research Council (QSpecNewMat ERC-2015-AdG-694097) and Grupos Consolidados (IT578-13).

Recently, the two-dimensional (2D) semiconductors arsenene and antimonene, with band gaps larger than 2.0 eV, have attracted tremendous interest, especially for potential applications in optoelectronic devices with a photoresponse in the blue and UV range. Motivated by this exciting discovery, types of highly stable wide-band-gap 2D nitride semiconductors were theoretically designed. We propose single-layer $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) via first-principles simulations. We compute $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) with indirect band gaps of 2.825, 2.351, and 2.336 eV, respectively. By applying biaxial strain, they are able to induce the transition from a wide-band-gap semiconductor to a metal, and the range of absorption spectra of $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) obviously extend from the ultraviolet region to the blue-purple light region. With an underlying graphene, we find that $1T\ensuremath{-}X{\mathrm{N}}_{2}$ can completely shield the light absorption of graphene in the range of 1--1.6 eV. Our research paves the way for optoelectronic devices working under blue or UV light, and mechanical sensors based on these 2D crystals.

Compared with conventional metal plasmonic materials, surface plasmons in graphene are advantageous in terms of higher confinement, relative low loss, flexible featuring, and good tunability. However, the working frequencies of the pristine graphene (undoped graphene) surface plasmons are located in the terahertz and infrared regions, which limit their applications. Here we show high-frequency plasmons in nitrogen (N)-doped graphene nanostructures investigated by time-dependent density functional theory. We found the optical absorption strength of systems containing two layers to be more than twofold stronger than that of systems with monolayers. The optical absorption strength increases as the interlayer distance increases, and the absorption spectra are red-shifted for impulse excitations polarized in the armchair edge direction $(x$ axis). For microstructures of more than two layers, the optical absorption strength increases as number of layers of the N-doped graphene nanostructures increases. In addition, when the number of layers becomes elevated at low-energy resonances, the absorption spectra are seen to blue-shift. The plasmon energy resonance points are located in the visible and ultraviolet regions. The N-doped graphene provides an effective strategy for nanoscale plasmon devices in the visible and ultraviolet regions, despite their weaker absorption intensities when compared with the pristine graphene.

Graphene zigzag edges are known to show the spin polarized ferromagnetic states, which are well described by the mean field treatment of Hubbard model. The parameter of onsite Coulomb interaction U is estimated to be comparable to the kinetic hopping parameter t so as to fit the electronic band structures obtained by the spin–polarized density functional theory (DFT). In this paper, we propose a simple way to transfer the electronic band structures obtained by DFT onto the mean-field Hubbard Hamiltonian by adopting site-dependent U parameter, which is taken as the decaying function from the edge. This approach is applicable to both anti-ferromagnetic and ferromagnetic states between two edges of graphene nanoribbons and will serve to perform the further large-scale simulation of electro-magnetic transport properties of graphene-based nanodevices.

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.

We performed ab initio calculations combined with the nudged elastic band method to study the diffusion of oxygen atoms on graphene. The most stable adsorption configuration is epoxy structure, and the diffusion barrier height for single epoxy oxygen is 0.9 eV. The calculated diffusion barrier of the second epoxy oxygen atom shows that the epoxy oxygen atoms tend to align along the armchair direction on a flat graphene surface. To estimate the curvature effect of a graphene sheet, we have compared above results with the diffusion of an oxygen atom on carbon nanotubes (CNTs). The curvature effect induces the stretching of the C–C bond beneath epoxy oxygen and reduces the internal strain due to the local curvature, which significantly lowers the total energy of the system. For the armchair CNT, the oxygen atoms would align along the tube axis (zigzag direction). These facts suggest that the favored direction of oxygen alignment can be changed by the curvature of graphene.

Non-equilibrium dynamics induced by the femtosecond laser shot has attracted high attentions in condensed matter community. Interaction between a strong field of light and materials cannot be treated by conventional perturbation theory that assumes both electron wave functions and ionic positions as insensitive to the field. Direct approach for computing real-time propagations of electron wave packet and ionic positions under presence of strong optical field is one of promising solutions. In this review, I present theoretical approaches based on the time-dependent density functional theory and show some examples of ultra-fast dynamics in materials induced by the femtosecond laser shots: exfoliation of graphene layer from graphite and photochemical reaction of molecules encapsulated inside carbon nanotubes.

Maximum capacities of the hydrogen storage in organometallic compounds consisting of Co and Ni atoms bound to CmHm ring (m = 4, 5; capped type) were, respectively, found as 3.48 and 3.49 wt % (Guo et al., Struct Chem, 2009, 20, 1107). Here, we extend this study to structures having a transition metal (TM) inserted in CmHm ring (inserted type), having TM located on either a C4H or a C5H molecule, and the CH3 ligand bound to the organometallic compounds. We find that for the CoC4H4 and NiC4H4 complexes, the capped types are 1.39 eV and 1.41 eV higher in energy than the inserted types, respectively, while the ground states for CoC5H5 and NiC5H5 complexes are found to be the capped type, which are lower than the inserted types, respectively, by 1.27 eV and 1.31 eV. The maximum capacity of hydrogen storage reached 5.13 wt % for both of CoC4H(H2)3 complex and the inserted-type CoC4H4(H2)3 complex with a reasonable binding energy (0.3–1.0 eV per H2). The positively charged C4H4 and C5H5 molecules do not only improve the capacity of hydrogen storage but also make all H2 adsorbing in molecular form and keep the adsorption energy in an ideal range. After adding the CH3 ligand to the compounds, the average adsorption energy of H2 decreased to an ideal range 0.61–0.94 eV per H2 and the stability of the compounds is also improved. Finally, we analyze the HOMO–LUMO gaps and display the kinetic stability when H2 was added to organometallic compounds. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

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.

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.

We address the mechanism responsible for the chirality-selective destruction of carbon nanotubes upon oxidation. The reaction barriers for breaking the C–C bonds of carbon nanotubes are obtained based on density functional calculations. The barrier height is associated with the local-curvature radii along with the breaking C–C bonds rather than the diameters of nanotubes. Furthermore, hole doping can alter the order of the reaction barrier heights. These findings can be utilized for the chirality selection of nanotubes using oxidative purification.

The chirality-dependent combustion of single-walled carbon nanotubes (SWCNTs) during oxidation in both air and hydrogen peroxide was investigated using photoluminescence and Raman spectroscopy. Under air oxidation conditions, SWCNTs with a higher chiral angle and smaller diameter were observed to decompose more rapidly. The decomposition rate of each chiral index was determined from the reaction rate analysis, and it was found that the reaction is governed by a "local curvature radius" along the C-C bond. The reaction barriers for breaking the C-C bonds after cycloaddition with oxygen molecules were obtained for 10 types of SWCNTs using first-principles calculations. The barrier heights were found to depend on the local curvature radius, which showed good agreement with the experimental results. On the other hand, for the oxidation reaction in hydrogen peroxide, oxygen radicals decomposed the smaller-radius SWCNTs more rapidly without any chirality selection. As a result, two different chirality distributions for SWCNTs with similar diameters were obtained by these oxidation processes.