The induction of a graphite-like phase on diamond films by a Fe-coating/post-annealing process to improve their electron field emission properties

[[abstract]]The electron field emission (EFE) process for diamondfilms was tremendously enhanced by Fe-coating and post-annealing processes. Microstructural analysis indicates that the mechanism for the improvement in the EFE process is the formation of nanographites with good crystallinity that surround the Fe (or Fe3C) nanoclusters. Presumably the nanographites were formed via the reaction of Fe clusters with diamondfilms, viz. by the dissolution of carbons into Fe (or Fe3C) clusters and the reprecipitation of carbon species to the surface of the clusters, a process similar to the growth of carbon nanotubes via Fe clusters as catalyst. Not only is a sufficiently high post-annealing temperature (900°C) required but also a highly active reducing atmosphere (NH3) is needed to give a proper microstructure for enhancing the EFE process. The best EFE properties are obtained by post-annealing the Fe-coated diamondfilms at 900°C in an NH3 environment for 5 min. The EFE behavior of the films can be turned on at E 0 = 1.9 V/μm, attaining a large EFE current density of 315 μA/cm2 at an applied field of 8.8 V/μm (extrapolation using the Fowler–Nordheim model leads to J e = 40.7 mA/cm2 at a 20 V/μm applied field).[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Tidal and Magnetic Interactions between a Hot Jupiter and its Host Star in the Magnetospheric Cavity of a Protoplanetary Disk

We present a simplified model to study the orbital evolution of a young hot Jupiter inside the magnetospheric cavity of a proto-planetary disk. The model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet. We focus on the orbital evolution starting from the orbit in the 2:1 resonance with the inner edge of the disk, followed by the inward and then outward orbital migration driven by the tidal and magnetic torques as well as the Roche-lobe overflow of the tidally inflated planet. The goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size, planet mass, and orbital eccentricity. In the present work, we only target the mass range from 0.7 to 2 Jupiter masses. In the case of the large cavity corresponding to the rotational period ~ 7 days, the planet of mass >1 Jupiter mass with moderate initial eccentricities (>~ 0.3) can move to the region < 0.03 AU from its central star in 10^7 years, while the planet of mass <1 Jupiter mass cannot. We estimate the critical eccentricity beyond which the planet of a given mass will overflow its Roche radius and finally lose all of its gas onto the star due to runaway mass loss. In the case of the small cavity corresponding to the rotational period ~ 3 days, all of the simulated planets lose all of their gas even in circular orbits. Our results for the orbital evolution of young hot Jupiters may have the potential to explain the absence of low-mass giant planets inside ~ 0.03 AU from their dwarf stars revealed by transit surveys.Comment: 29 pages, 6 figures, 1 table. accepted for publication by Ap

A Three-Dimensional in Vitromodel of Atherogenesis

Atherosclerosis is the narrowing of arteries caused by accumulation of cholesterol, calcium and other cellular debris in the inner arterial wall. While extensive studies have been focusing on the inflammatory mechanisms of the disease, pathological and experimental evidence has shown that regions of disturbed flow are susceptible to the atherogenesis. To further understand the relationship between hemodynamics and atherogenesis, this research aims to generate a dynamic, 3D in vitro model of atherogenesis. This will allow for the investigation of specific cellular and molecular mechanisms of plaque formation that will pave the way for new therapies for the disease. A novel fabrication method that produces a 3D vascular construct was developed, which contains the cellular (endothelial cells, smooth muscle cells, and fibroblasts) and extracellular components of native vessels (type I collagen). Briefly, a combination of cells and solubilized collagen are polymerized in a tube mold to create the vascular tissue construct. The resulting tube, or the “cytotube”, contains a radial-symmetric nozzle-like structure in the center of the construct, which was design to generate disturbed flow as fluid passes through the structure. CFD (computational fluid dynamics) modeling indicated an area of recirculating (disturbed) flow downstream the nozzle. Cell viability, morphology and protein expression in the cytotubes were investigated with confocal microscopy. These studies found that all fibroblasts, smooth muscle cells, and endothelial cells remained viable and have expressed various phenotypic morphologies in the cytotubes over 7 days of static culture. The proposed fabrication method and the resulting model not only can serve as an in vitro 3D culture system and pathogenesis monitoring system, but also has the potential to influence vascular tissue-engineering studies

Spatially separated polar samples of the cis and trans conformers of 3-fluorophenol

We demonstrate the spatial separation of the cis- and trans-conformers of 3-fluorophenol in the gas phase based on their distinct electric dipole moments. For both conformers we create very polar samples of their lowest-energy rotational quantum states. A >95 % pure beam of trans-3-fluorophenol and a >90 % pure beam of the lowest-energy rotational states of the less polar cis-3-fluorophenol were obtained for helium and neon supersonic expansions, respectively. This is the first demonstration of the spatial separation of the lowest-energy rotational states of the least polar conformer, which is necessary for strong alignment and orientation of all individual conformers.Comment: 5 pages, 5 figure

Spatially-controlled complex molecules and their applications

The understanding of molecular structure and function is at the very heart of the chemical and molecular sciences. Experiments that allow for the creation of structurally pure samples and the investigation of their molecular dynamics and chemical function have developed tremendously over the last few decades, although "there's plenty of room at the bottom" for better control as well as further applications. Here, we describe the use of inhomogeneous electric fields for the manipulation of neutral molecules in the gas-phase, \ie, for the separation of complex molecules according to size, structural isomer, and quantum state. For these complex molecules, all quantum states are strong-field seeking, requiring dynamic fields for their confinement. Current applications of these controlled samples are summarised and interesting future applications discussed.Comment: Accepted by Int. Rev. Phys. Che