High-resolution transmission electron microscopy investigation of the nanostructure of undoped and Pt-doped nanocrystalline pulsed laser deposited SnO2 thin films

Pulsed laser deposition (PLD) was used to grow nanocrystalline SnO₂ thin films onto alumina substrates. The reactive PLD process was carried out at different substrate deposition temperatures (T_d) between 20 and 600 °C under an oxygen background pressure of 150 mtorr. The same PLD technique was used to produce SnO₂ films in situ-doped with Pt (at the level of ∼2 at. %) through the concomitant ablation of both SnO₂ target and Pt strips. Conventional and high-resolution transmission electron microscopy (HRTEM) observations have revealed that the microstructure of the PLD SnO₂ films is highly sensitive to their deposition temperature. Indeed, its changes from a porous granular structure with extremely fine equiaxed grains (∼4 nm diameter), at T_d=20 °C to a very compact and textured columnar structure characterized by SnO₂ columns (∼25 nm diameter) composed of grains of ∼12 nm of diameter, at T_d=600 °C. In addition, the PLD SnO₂ films were found to exhibit the highest nanoporosity at T_d=300 °C which also coincides with the granular-to-columnar microstructural transition. On the other hand, the microstructure of the Pt-doped SnO₂ films, deposited at 300 °C, was found to contain a high density of defects, such as twin boundaries and edge dislocations. By combining HRTEM and EDS microanalysis, we were able to show that the Pt-dopant self-organizes into spherical nanoparticles (1-2 nm diameter) randomly distributed at the SnO₂ grain boundaries. Finally, doping the films with such platinum nanoclusters is found to affect the SnO₂ nanostructure by particularly reducing the SnO₂ mean grain size (from ∼10 nm when undoped to ∼6 nm for the doped films).     

Band broadening evaluation by back-and-forth capillary electrophoresis

The purpose of this study is to develop a method for precise evaluation of band broadening in capillary electrophoresis. A capillary electrophoresis system with on-column twin detectors is constructed. Back-and-forth electrophoresis permits zones to make a round trip between the twin detectors placed at distant positions on the capillary. The system is capable of eliminating extra-column effects and discriminating between reversible and irreversible band-broadening mechanisms.     

Inversion of a block Löwner matrix

In this paper, we give a fast algorithm to compute the parameters of an inversion formula for any nonsingular block Löwner matrix. The connection with matrix rational interpolation is given.     

关于SL(2,R)上速降函数的反演公式

在局部紧可分群的一般理论中，分解正则表示以及获得反演公式（或 Ｐｌａｎ－ｃｈｅｒｅｌ定理的明确表示）是调和分析的基本目标之一．ＳＬ（２，　）是最简单的非交换局部紧么模半单Ｌｉｅ群．Ｈａｒｉｓｈ－Ｃｈａｎｄｒａ在 Ｃ∞ｃ（ＳＬ（２，　））上获得了反演公式，Ｘｉａｏ和ｈｅｎｇ在文［１］中证明了Ｃ３ｃ（ＳＬ（２， ）上的反演公式．在文［２］中Ｚｈｅｎｇ引入了Ｌｉｅ群Ｇ上函数的广义微分（Ａ导数）概念．在本文中，我们利用文［２］中的微分概念来研究ＳＬ（２，　）上可微函数的Ｆｏｕｒｉｅｒ变换的阶，并获得了ＳＬ（２，　）上速降函数的反演公式．     

A transform involving Chebyshev polynomials and its inversion formula

We define a functional analytic transform involving the Chebyshev polynomials Tn(x), with an inversion formula in which the Möbius function μ(n) appears. If s∈C with Re(s)>1, then given a bounded function from [−1,1] into C, or from C into itself, the following inversion formula holds:

     

The flipped longitudinal polarization sequence

By flipping the longitudinal magnetization with a chain of 180° pulses it is possible to effectively restore the effects of relaxation so that the same longitudinal magnetization is periodically recovered. The pulse sequence for achieving this, called Flipped LOngitudinal Polarization (FLOP), can be incorporated into any pulse sequence whenever it is desired to stop the attenuation in longitudinal magnetization caused by relaxation. We illustrate its use for fast, single-shot measurements of the longitudinal relaxation time and for three-dimensional T₁ mapping.     

Combustion mechanism of ultralean rotating counterflow twin premixed flame

In our previous numerical studies [Nishioka Makihito, Zhenyu Shen, and Akane Uemichi. “Ultra-lean combustion through the backflow of burned gas in rotating counterflow twin premixed flames.” Combustion and Flame 158.11 (2011): 2188–2198. Uemichi Akane, and Makihito Nishioka. “Numerical study on ultra-lean rotating counterflow twin premixed flame of hydrogen–air.” Proceedings of the Combustion Institute 34.1 (2013): 1135–1142]. we found that methane– and hydrogen–air rotating counterflow twin flames (RCTF) can achieve ultralean combustion when backward flow of burned gas occurs due to the centrifugal force created by rotation. In this study, we investigated the mechanisms of ultralean combustion in these flames by the detailed numerical analyses of the convective and diffusive transport of the main species. We found that, under ultralean conditions, the diffusive transport of fuel exceeds its backward convective transport in the flame zone, which is located on the burned-gas side of the stagnation point. In contrast, the relative magnitudes of diffusive and convective transport for oxygen are reversed compared to those for the fuel. The resulting flows for fuel and oxygen lead to what we call a ‘net flux imbalance’. This net flux imbalance increases the flame temperature and concentrations of active radicals. For hydrogen–air RCTF, a very large diffusivity of hydrogen enhances the net flux imbalance, significantly increasing the flame temperature. This behaviour is intrinsic to a very lean premixed flame in which the reaction zone is located in the backflow of its own burned gas.     

Single Production of Top Quark via e-γ Collision in Left-Right Twin Higgs Model

In the context of the left-right twin Higgs （LRTH） model, we fist study single production of the standard model （SM） top quark via e-γ collisions. We find that the corrections of the LRTH model to the cross section of the process e-γ→vebt might be observed only for f ≤750 GeV and the heavy top quark mass scale M ≥500 GeV in future high energy linear e^＋e^- collider （LC） experiment with the center-of-mass （CM） energy √s = 500 GeV and a yearly integrated luminosity of ￡ = 100 fb^-1. We also consider single production of the heavy top quark T via e-γ collisions. Our numerical results show that the possible signals of the heavy top quark T might be observed via the decay channel T →Ф^＋b→tbb in future LC experiment with √s = 3 TeV and ￡ = 500 fb^-1.