Synthesis mechanism from graphene quantum dots to carbon nanotubes by ion-sputtering assisted chemical vapor deposition.

We present the first work of the synthesis mechanism from graphene quantum dots (GQDs) to carbon nanotubes (CNTs) by an ion-sputtering assisted chemical vapor deposition. During the annealing process, a Pt thin film deposited by the ion-sputtering was dewetted and agglomerated to form many nanometer-sized particles, leading to Pt nanoparticles (PtNPs) that can act as catalysts for creating carbon allotropes. The shape of the allotropes can be effectively tailored from GQDs to CNTs by controlling three key parameters such as the dose of catalytic ions (D), amounts of carbon source (S), and thermal energy (T). In our work, it was clearly proved that the growth control from GQDs to CNTs has a comparably proportional relationship with D and S, but has a reverse proportional relationship with T. Furthermore, high-purity GQDs without any other by-products and the CNTs with the cap of PtNPs were generated. Their shapes were appropriately controlled, respectively, based on the established synthesis mechanism.

Cross-section measurements for 68Zn(p,2p)67Cu and 68Zn(p,2n)67Ga reactions using a newly developed separation method for the superposed [Formula: see text]-ray spectra.

We have developed a new analytical peak separation analysis for superposed [Formula: see text]-ray peaks on [Formula: see text]Cu and [Formula: see text]Ga to measure the [Formula: see text]Zn(p,2p)[Formula: see text]Cu and [Formula: see text]Zn(p,2n)[Formula: see text]Ga reactions, unlike in most previous works that were employing a radiochemical separation to measure them. Based on the nuclear data such as the [Formula: see text]-ray intensity and the half-life for each nuclide, we may develop a new analytical method that enables us to estimate the respective counts arising from each nuclide, thereby obtaining the nuclear reactions. The newly developed analytical method can universally be applied to separate the superposed [Formula: see text]-ray spectra of any two nuclides, especially superior in separating the nuclides with different half-lives. In comparison with the data in the literature, the two reactions in the present work are in good agreement with those of some previous works. In addition, we compared the present [Formula: see text]Zn(p,2n)[Formula: see text]Ga reaction without the peak separation to the data in the literature without the chemical separation, and find that a good agreement is evident, enhancing the reliability of the [Formula: see text]Zn(p,x)[Formula: see text]Zn and [Formula: see text]Zn(p,3n)[Formula: see text]Ga reactions, which are further measured in the present work.

Field-of-view enhanced integral imaging with dual prism arrays based on perspective-dependent pixel mapping.

A field-of-view (FOV)-enhanced integral imaging system is proposed by the combined use of micro-lens array (MLA) and dual-prism array (DPA). The MLA coupled with a DPA virtually function as a new type of the MLA whose FOV is much more increased than that of the original MLA, which enables the capturing of perspective-expanded elemental image arrays (EIAs) of input 3-D scenes and the FOV-enhanced reconstruction of them. For its practical operation, a two-step digital process called perspective-dependent pixel-mapping (PDPM) is also presented. With this PDPM method, picked-up EIAs with a couple of MLAs and DPAs are remapped into the new forms of EIAs to be properly reconstructed in the conventional integral imaging system. Operational performances of the proposed system are ray-optically analyzed. In addition, the feasibility of the proposed system is also confirmed from the computational and optical experiments with test 3-D objects on the implemented prototype. Experimental results finally show a two-times increase of the FOV range of the proposed system when it is compared with that of the conventional system.

Compact full-color holographic 3-D display based on undersampled computer-generated holograms and oblique projection imaging.

A compact full-color electro-holographic three-dimensional (3-D) display with undersampled computer-generated holograms (US-CGHs) and oblique projection imaging (OPI) is proposed. For its realization, undersampling conditions of the CGH enabling the complete recovery of image information are derived, and the OPI-based longitudinal-to-lateral depth conversion (LTL-DC) scheme allowing the simple reconstruction of full-color images is also proposed. Three-color off-axis US-CGHs are generated with their center-shifted principle fringe patterns (CS-PFPs) of the novel look-up table (NLUT) method, where center-shifts are calculated with the derived undersampling conditions of the CGH based on the generalized sampling theorem, and then multiplexed into the color-multiplexed hologram (CMH). The CMH is loaded on a SLM (spatial light modulator) and reconstructed by being illuminated with a multi-wavelength light source, where an original full-color image is reconstructed being spatially separated from the other color-dispersed images on the projected image plane with the OPI-based LTL-DC process, which enables us to view the original full-color image just with a simple filter mask. Performance analysis and successful experiments with the test 3-D objects in motion confirm the feasibility of the proposed system.

A mechanism of surface hardness enhancement for H+ irradiated polycarbonate.

H+ irradiation increases the surface hardness of polycarbonate. Nano indentation measurement shows that the hardness increases up to 3.7 GPa at the dose of 5 × 1016 # cm-2 and at the irradiation energy of 150 keV. In addition, the hardness increases with the dose and the energy of H+ irradiation. In accordance with the nano indentation measurement, the Fourier-transform infrared spectroscopy (FTIR) depends on the dose and energy of H+ irradiation. The peak at ∼1500 cm-1 for the aromatic ring and the peak at ∼1770 cm-1 for the C[double bond, length as m-dash]O stretch decrease with increasing dose and energy, while the increase of the dose and energy develops a new C[double bond, length as m-dash]O stretch vibration at ∼1700 cm-1 and forms aromatic hydrocarbons at ∼1600 cm-1. X-ray diffraction experiments are also consistent with the nano indentation measurement and FTIR spectra. Based on the experiments, we discuss a possible mechanism of the surface hardness enhancements by ion beam irradiation.

Evidence of a turbulent ExB mixing avalanche mechanism of gas breakdown in strongly magnetized systems.

Although gas breakdown phenomena have been intensively studied over 100 years, the breakdown mechanism in a strongly magnetized system, such as tokamak, has been still obscured due to complex electromagnetic topologies. There has been a widespread misconception that the conventional breakdown model of the unmagnetized system can be directly applied to the strongly magnetized system. However, we found clear evidence that existing theories cannot explain the experimental results. Here, we demonstrate the underlying mechanism of gas breakdown in tokamaks, a turbulent ExB mixing avalanche, which systematically considers multi-dimensional plasma dynamics in the complex electromagnetic topology. This mechanism clearly elucidates the experiments by identifying crucial roles of self-electric fields produced by space-charge that decrease the plasma density growth rate and cause a dominant transport via ExB drifts. A comprehensive understanding of plasma dynamics in complex electromagnetic topology provides general design strategy for robust breakdown scenarios in a tokamak fusion reactor.

Superheating and melting within aluminum core-oxide shell nanoparticles for a broad range of heating rates: multiphysics phase field modeling.

The external surface of metallic particles is usually covered by a thin and strong oxide shell, which significantly affects superheating and melting of particles. The effects of geometric parameters and heating rate on characteristic melting and superheating temperatures and melting behavior of aluminum nanoparticles covered by an oxide shell were studied numerically. For this purpose, the multiphysics model that includes the phase field model for surface melting, a dynamic equation of motion, a mechanical model for stress and strain simulations, interface and surface stresses, and the thermal conduction model including thermoelastic and thermo-phase transformation coupling as well as transformation dissipation rate was formulated. Several nontrivial phenomena were revealed. In comparison with a bare particle, the pressure generated in a core due to different thermal expansions of the core and shell and transformation volumetric expansion during melting, increases melting temperatures with the Clausius-Clapeyron factor of 60 K GPa-1. For the heating rates Q ≤ 109 K s-1, melting temperatures (surface and bulk start and finish melting temperatures, and maximum superheating temperature) are independent of Q. For Q ≥ 1012 K s-1, increasing Q generally increases melting temperatures and temperature for the shell fracture. Unconventional effects start for Q ≥ 1012 K s-1 due to kinetic superheating combined with heterogeneous melting and geometry. The obtained results are applied to shed light on the initial stage of the melt-dispersion-mechanism of the reaction of Al nanoparticles. Various physical phenomena that promote or suppress melting and affect melting temperatures and temperature of the shell fracture for different heating-rate ranges are summarized in the corresponding schemes.

Coupled phase field, heat conduction, and elastodynamic simulations of kinetic superheating and nanoscale melting of aluminum nanolayer irradiated by picosecond laser.

An advanced continuum model for nanoscale melting and kinetic superheating of an aluminum nanolayer irradiated by a picosecond laser is formulated. Barrierless nucleation of surface premelting and melting occurs, followed by a propagation of two solid-melt interfaces toward each other and their collision. For a slow heating rate of Q = 0.015 K ps(-1) melting occurs at the equilibrium melting temperature under uniaxial strain conditions T = 898.1 K (i.e., below equilibrium melting temperature Teq = 933.67 K) and corresponding biaxial stresses, which relax during melting. For a high heating rate of Q = 0.99-84 K ps(-1), melting occurs significantly above Teq. Surprisingly, an increase in heating rate leads to temperature reduction at the 3 nm wide moving interfaces due to fast absorption of the heat of fusion. A significant, rapid temperature drop (100-500 K, even below melting temperature) at the very end of melting is revealed, which is caused by the collision of two finite-width interfaces and accelerated melting in about the 5 nm zone. For Q = 25-84 K ps(-1), standing elastic stress waves are observed in a solid with nodal points at the moving solid-melt interfaces, which, however, do not have a profound effect on melting time or temperatures. When surface melting is suppressed, barrierless bulk melting occurs in the entire sample, and elastodynamic effects are more important. Good correspondence with published, experimentally-determined melting time is found for a broad range of heating rates. Similar approaches can be applied to study various phase transformations in different materials and nanostructures under high heating rates.

Botulinum toxin A affects early capsule formation around silicone implants in a rat model.

Capsular contracture is one of the most common complications resulting from implants placed during mammoplasty and rhinoplasty, and there is no definitive solution or a method for preventing it. Recent reports suggest that botulinum toxin A (BoTA) is effective at reducing keloid scars clinically. Peri-implant capsules are histologically similar to keloid scars and hypertrophic scars. Therefore, we hypothesized that BoTA may reduce peri-implant capsule formation.To test our hypothesis, we divided 24 male Sprague-Dawley rats into an experiment group and a control group. We created two 15 × 15-mm subpanniculus pockets in each rat. Botulinum toxin A (0.5 mL; 5 U) was injected into the carnosa layer of the experimental group's pockets and 0.5 mL normal saline was similarly injected in the control group. Hemispherical silicone implants, 15 mm in diameter, were inserted into the pockets. After 6 weeks, the peri-implant capsule was excised and examined by histologic evaluation, immunohistochemical stain, scanning electron microscope, and real-time polymerase chain reaction.Capsular thickness, number of inflammatory cells, number of vessels, and transforming growth factor ß1 expression were reduced in the experimental group compared to the control group (P < 0.01). The experimental group's collagen pattern was loose and well organized. The total myofibroblast content was lower in the experimental group than in the control group; however, this difference was not statistically significant (P = 0.32). Additionally, the experimental group had a smaller fibrosis index than the control group (P < 0.05).Our results suggest that BoTA may provide an alternative treatment for reducing capsule formation and preventing contracture, and further studies may reveal the mechanism of action.

Time-sequential autostereoscopic 3-D display with a novel directional backlight system based on volume-holographic optical elements.

A novel directional backlight system based on volume-holographic optical elements (VHOEs) is demonstrated for time-sequential autostereoscopic three-dimensional (3-D) flat-panel displays. Here, VHOEs are employed to control the direction of light for a time-multiplexed display for each of the left and the right view. Those VHOEs are fabricated by recording interference patterns between collimated reference beams and diverging object beams for each of the left and right eyes on the volume holographic recording material. For this, self-developing photopolymer films (Bayfol® HX) were used, since those simplify the manufacturing process of VHOEs substantially. Here, the directional lights are similar to the collimated reference beams that were used to record the VHOEs and create two diffracted beams similar to the object beams used for recording the VHOEs. Then, those diffracted beams read the left and right images alternately shown on the LCD panel and form two converging viewing zones in front of the user's eyes. By this he can perceive the 3-D image. Theoretical predictions and experimental results are presented and the performance of the developed prototype is shown.

Depth-extended integral imaging system based on a birefringence lens array providing polarization switchable focal lengths.

An integral imaging system enabling extended depth of field was proposed and demonstrated based on a birefringence lens array (BLA) whose focal length was switched via the light polarization. The lens array system was constructed by combining two different liquid crystal(LC) embedded lens arrays, BLA I and II, which were fabricated by injecting a ZLI-4119 LC and an E-7 LC in between a lens array substrate and an ITO (indium-tin-oxide) glass plate respectively. The BLA I played a role as a convex lens only for the polarization parallel to the ordinary axis of the corresponding LC, but it serves as a plain medium for that along its extraordinary one since the refractive indexes of the lens and the LC are almost identical. Meanwhile, the BLA II played a role as a concave lens only for the polarization parallel to the extraordinary axis of the LC but as a plain medium for that along its ordinary one. As a result, the focal length could be switched via the polarization, and it was measured to be 680 mm and -29 mm. For the proposed system with the prepared BLAs, both real and virtual three-dimensional (3D) images were efficiently reconstructed at the positions of z=1300 mm and z=-30 mm with no significant degradation in the resolution, indicating its depth of field range.