다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

There are growing concerns over the environmental, climate, and health impacts caused by using non-renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium-ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid-electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.

Silicon-based Nanomaterials for Lithium-Ion Batteries - A Review

Tremendous progress has been made in the development of lithium-based rechargeable batteries in recent decades. Discoveries of new electrode materials as well as new storage mechanisms have substantially improved battery performance. In particular, nanomaterials design has emerged as a promising solution to tackle many fundamental problems in conventional battery materials. Here we discuss in detail several key issues in batteries, such as electrode volume change, solid–electrolyte interphase formation, electron and ion transport, and electrode atom/molecule movement, and then analyse the advantages presented by nanomaterials design. In addition, we discuss the challenges caused by using nanomaterials in batteries, including undesired parasitic reactions with electrolytes, low volumetric and areal energy density, and high costs from complex multi-step processing, and their possible solutions. Nanomaterials design may offer a solution to tackle many fundamental problems in conventional batteries. Cui et al. review both the promises and challenges of using nanomaterials in lithium-based rechargeable batteries.

Promises and challenges of nanomaterials for lithium-based rechargeable batteries

Progress in material selection for solid oxide fuel cell technology: A review

The carbothermal reduction of silica into silicon requires the use of temperatures well above the silicon melting point (> or =2,000 degrees C). Solid silicon has recently been generated directly from silica at much lower temperatures ( 500 m(2) g(-1)), and contained a significant population of micropores (< or =20 A). The silicon replicas were photoluminescent, and exhibited rapid changes in impedance upon exposure to gaseous nitric oxide (suggesting a possible application in microscale gas sensing). This process enables the syntheses of microporous nanocrystalline silicon micro-assemblies with multifarious three-dimensional shapes inherited from biological or synthetic silica templates for sensor, electronic, optical or biomedical applications.

Chemical reduction of three-dimensional silica micro-assemblies into microporous silicon replicas

Raman spectra of nickel sulfides reported in previous studies are inconsistent due possibly to the difficulty in obtaining samples of the required purity in composition and phase. In this study, Ra...

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Raman Spectroscopy of Nickel Sulfide Ni3S2

Interactions between O(2) and CeO(2) are examined experimentally using in situ Raman spectroscopy and theoretically using density-functional slab-model calculations. Two distinct oxygen bands appear at 825 and 1131 cm(-1), corresponding to peroxo- and superoxo-like species, respectively, when partially reduced CeO(2) is exposed to 10 % O(2). Periodic density-functional theory (DFT) calculations aid the interpretation of spectroscopic observations and provide energetic and geometric information for the dioxygen species adsorbed on CeO(2). The O(2) adsorption energies on unreduced CeO(2) surfaces are endothermic (0.91<DeltaE(ads)<0.98 eV), while those on reduced surfaces are exothermic (-4. 0<DeltaE(ads)<-0.9 eV), depending on other relevant surface processes such as chemisorption and diffusion into the bulk. Partial reduction of surface Ce(4+) to Ce(3+) (together with formation of oxygen vacancies) alters geometrical parameters and, accordingly, leads to a shift in the vibrational frequencies of adsorbed oxygen species compared to those on unreduced CeO(2). Moreover, the location of oxygen vacancies affects the formation and subsequent dissociation of oxygen species on the surfaces. DFT predictions of the energetics support the experimental observation that the reduced surfaces are energetically more favorable than the unreduced surfaces for oxygen adsorption and reduction.

https://ir.nctu.edu.tw:443/bitstream/11536/11780/1/000240668700018.pdf

Characterization of O2–CeO2 Interactions Using In Situ Raman Spectroscopy and First‐Principle Calculations

The critical issues facing the development of economically competitive solid oxide fuel cell (SOFC) systems include lowering the operation temperature and creating novel anode materials and microstructures capable of efficiently utilizing hydrocarbon fuels. In this paper, we report our recent progress in developing more efficient anodes for direct utilization of methane and propane in low-temperature SOFCs. Anode-supported SOFCs with an electrolyte of 20 μm thick Gd-doped ceria (GDC) were fabricated by copressing, and both Ni- and Cu-based anodes were prepared by a solution impregnation process. Results indicate that both microstructure and composition of the anodes, as fabricated using a solution impregnation technique, greatly influence fuel cell performance. At 600°C, SOFCs fueled with humidified methane, and propane reach peak power densities of 602, 519, and 433 mW/cm2, respectively. © 2004 The Electrochemical Society. All rights reserved.

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GDC-Based Low-Temperature SOFCs Powered by Hydrocarbon Fuels

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution for the utilization of a wide variety of fuels beyond hydrogen. One of the chief obstacles to true fuel flexibility lies in anode deactivation by coking as well as a limited mechanistic understanding of coking and its prevention. Here we report Raman spectroscopic mapping and monitoring of carbon deposition on SOFC anode surfaces under both ex situ and in situ conditions. Carbon mapping was successfully demonstrated with a model Ni–YSZ electrode exposed to a CH4-containing atmosphere at high temperature (625 °C), while carbon deposition over time in a wet C3H8 atmosphere was directly monitored on a similar anode system as well as a BaO-modified system. This spectroscopic technique provides valuable insight into the mechanism of carbon deposition, which is vital in achieving rational design of carbon-tolerant anode materials.

http://www.rsc.org/suppdata/ee/c2/c2ee21499g/c2ee21499g.pdf

Harry Abernathy

Papers

Chemical reduction of three-dimensional silica micro-assemblies into microporous silicon replicas

Raman Spectroscopy of Nickel Sulfide Ni3S2

Characterization of O2–CeO2 Interactions Using In Situ Raman Spectroscopy and First‐Principle Calculations

GDC-Based Low-Temperature SOFCs Powered by Hydrocarbon Fuels

Raman spectroscopic monitoring of carbon deposition on hydrocarbon-fed solid oxide fuel cell anodes