Amorphous carbon nitride film preparation by plasma-assisted pulsed laser deposition method

Amorphous carbon nitride (aCN_x) films were prepared by pulsed laser ablation of graphite in N₂ RF plasma. The film property was compared with that prepared in N₂ gas. The N₂ plasma was generated by a mesh electrode, which was inserted between a graphite target and a Si substrate. The gas pressure p_N2 was varied from 10 to 100 mTorr. The film deposition rate exponentially decreased with p_N2 for both the plasma and gas environment. X-ray photoelectron spectroscopy analysis showed that the ratio of nitrogen content to the carbon one ([N]/[C]) of the aCN_x film surface deposited in the N₂ plasma was 2 times higher than that obtained in the N₂ gas. The film structure was shown by Raman spectroscopy analysis that sp² clustering was enhanced with increasing the [N]/[C]. The effect of plasma on aCN_x film deposition was discussed. PACS 81.15.Fg; 79.60.-i; 81.05.Uw     

Oscillatory behaviour in melting of a GaSb/InSb/GaSb system

The effect of coexistence of Marangoni and natural convections was studied numerically in melting of a GaSb/InSb/GaSb sandwich sample. Fluid flow and concentration fields are oscillatory when the solutal natural convection coexists with the thermal Marangoni convection. The coexistence of solutal and thermal natural convections, without Marangoni convection, however, does not lead to fluid flow oscillations in spite of the existence of two flow cells in opposite directions. The conclusion is that not the presence of two opposite flow cells but the flow structure itself, due to the presence of a free surface, is responsible for such an oscillatory behaviour.     

New numerical schemes based on a criterion for constructing essentially stable and accurate numerical schemes for convection-dominated equations

In order to obtain stable and accurate numerical solutions for the convection-dominated steady transport equations, we propose a criterion for constructing numerical schemes for the convection term that the roots of the characteristic equation of the resulting difference equation have poles. By imposing this criterion on the difference coefficients of the convection term, we construct two numerical schemes for the convection-dominated equations. One is based on polynomial differencing and the other on locally exact differencing. The former scheme coincides with the QUICK scheme when the mesh Reynolds number (Rm) is $\mathop \[{\textstyle{{\rm 8} \over {\rm 3}}}\] $, which is the critical value for its stability, while it approaches the second-order upwind scheme as Rm goes to infinity. Hence the former scheme interpolates a stable scheme between the QUICK scheme at Rm = $\mathop \[{\textstyle{{\rm 8} \over {\rm 3}}}\] $ and the second-order upwind scheme at Rm = ∞. Numerical solutions with the present new schemes for the one-dimensional, linear, steady convection-diffusion equations showed good results.     

Design and Synthesis of Mixed Oligomers with Thiophenes,Dithienothiophene S,S-Dioxides,Thieno[3,4]pyrazines and 2,1,3-Benzothiadiazoles: Flipper Screening for Mechanosensitive Systems

Monomers with large surface area and high quantum yield, that is fluorescent flippers, have been engineered into twisted push–pull oligomers to create membrane probes with high mechanosensitivity and long fluorescence lifetime. Here, the synthesis and characterization of thieno[3,4]pyrazines and 2,1,3-benzothiadiazoles are described in comparison with the original dithienothiophene S,S-dioxides. Dithienothiophene S,S-dioxide flippers are confirmed as the best reported so far, and poor results with single flipper probes support that two flippers are needed for the probe to really “swim”, that is, for high mechanosensitivity.     

Sputtering properties for polyimide by vacuum electrospray droplet impact (V‐EDI) using size‐selected cluster ions

Recently, the vacuum electrospray droplet impact (V‐EDI) was developed as a cluster ion beam source in our laboratory. To attain the ion beam stability and compact design of the ion source, a silica nano‐capillary with 15 µm i.d. was used as the emitter of the beam. It was found that stable electrospray was generated from the capillary tip without the use of laser heating when aqueous solution of 20% ethanol was used. The m/z distribution of electrospray droplets was measured by pulsing the primary beam. By assuming that the charged droplets contain 50% of the excess charges defined by the Rayleigh limit equation, the average mass, and charge of the droplets generated by the present V‐EDI are estimated as 2.5 × 10⁸ u and + 625 charges, respectively, i.e. [(H₂O)_14,000,000 + 625H]⁶²⁵⁺. By chopping the primary cluster beam, clusters composed of smaller m/z clusters (group 1: G1, [(H₂O)_46,000 + 36H]³⁶⁺) and those of larger m/z clusters (group 2: G2, [(H₂O)_560,000 + 125H]¹²⁵⁺) were generated. Surface analysis for polyimide (PI) film by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was made using G1, G2, and non‐selected cluster beams. No selective etching was observed when G1, G2, and non‐selected beams were used. However, larger surface roughening was observed when smaller size cluster beams were used. This suggests that larger size clusters cure the surface damage caused by the smaller ones. Copyright © 2016 John Wiley & Sons, Ltd.     

Observation of giant resonance phenomena in the two-step mechanism of electron-Xe collision

We report an (e,2e) binding energy spectrum of Xe obtained at an impact energy of 2.1 keV, which covers the binding energy range up to 220 eV. The result is directly compared with data from high-energy photoelectron spectroscopy. It is found that an (e,2e)-specific, very broad band appears at around 120 eV, although in other energy regions the binding energy spectra by the two methods are in good agreement. The presence of such a band is revealed for the first time, which can be attributed to the second-order effects of the electron-target interaction that involves giant resonance phenomena of the Xe 4d electron.     

Vitrification, encapsulation-vitrification and droplet-vitrification: a review

This paper discusses the importance of the successive steps of the vitrification technique and reviews the current development and use of vitrification and of the two derived protocols, encapsulation-vitrification and droplet-vitrification. Vitrification refers to the physical process by which a highly concentrated cryoprotective solution supercools to very low temperatures and finally solidifies into a metastable glass, without undergoing crystallization at a practical cooling rate. Samples are thus cryopreserved without detrimental intracellular ice formation. In a standard vitrification protocol, excised explants are precultured on medium enriched with sucrose, treated (loaded) with a loading solution composed of 2 M glycerol + 0.4 M sucrose, dehydrated with a highly concentrated vitrification solution [e.g. the PVS2 vitrification solution, which contains 30 percent (w/v) glycerol, 15 percent (w/v) ethylene glycol and 15 percent (w/v) DMSO and 0.4 M sucrose], frozen and rewarmed rapidly, unloaded with basal culture medium supplemented with 1.2 M sucrose, and then transferred to standard culture conditions. In the encapsulation-vitrification technique, the explants are encapsulated in alginate beads, loaded and dehydrated with a vitrification solution before rapid immersion in liquid nitrogen. In the droplet-freezing technique, excised explants are loaded, treated with the vitrification solution and frozen in individual microdroplets of vitrification solution placed on aluminium foils, which are immersed rapidly in liquid nitrogen. These three techniques have been applied to different tissues of over 100 plant species from temperate and tropical origins and the number of cases where they are being tested on a large scale or applied routinely is increasing.     

Blue light generation in a ridge waveguide MgO:LiNbO3 crystal pumped by a fiber Bragg grating stabilized laser diode

We report cw blue light generation by using a periodically poled MgO:LiNbO(3) crystal with a ridge waveguide pumped by a fiber Bragg grating stabilized laser diode with 0.25 nm spectrum width in the coherent collapse regime. Blue light generation of 73 mW with 27% conversion efficiency and a wide temperature tolerance of 5.7 degrees C were attained.