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241.
Sung-Hak Cho Won-Seok Chang Kyoung-Hyun Whang Seong-Hyang Sohn 《Applied Surface Science》2008,254(11):3370-3375
The photo-bleaching of single living cells excited by femtosecond laser irradiation was observed in situ to study the nonlinear interaction between ultrafast laser pulses and living human breast MDA-MB-231 cells. We conducted a systematic study of the energy dependence of plasma-mediated photo-disruption of fluorescently labeled subcellular structures in the nucleus of living cells using near-infrared (NIR) femtosecond laser pulses through a numerical aperture objective lens (0.75 NA). The behavior of photo-bleached living cells with fluorescently labeled nuclei was observed for 18 h after femtosecond laser irradiation under a fluorescence microscope. The photo-bleaching of single living cells without cell disruption occurred at between 470 and 630 nJ. To study the photo-disruption of subcellular organelles in single living cells using the nonlinear absorption excited by a NIR femtosecond laser pulse, the process of photo-bleaching without photo-disruption provides key information for clarifying the nonlinear interaction between NIR ultrashort, high-intensity laser light and transparent fluorescently labeled living cells. 相似文献
242.
Optimization of (002)-Oriented ZnO Film Synthesis in Sol-Gel Process and Film Photoluminescence Property 下载免费PDF全文
By orthogonal design theory, technological parameters of the (002)-oriented ZnO film prepared in sol-gel process are optimized. A set of technological parameters for growing highly (002)-oriented ZnO film is obtained. As a result, it is proven that the Zn2+ concentration is the most important factor to grow a highly (002)-oriented ZnO film. We take an appropriate Zn2+ concentration 0.35mol/L for the aimed film, of which photoluminescence property is better than those of the films derived from other Zn2+ concentrations precursor solution. The Zn2+ concentration either larger or smaller than 0.35mol/L leads to the (002)-oriented degree decrease of films. By employing an atom force microscope, a hexagonal atom arrangement, which indicates that the film site detected is a ZnO single crystal, is observed in the surface of the highly (002)-oriented film. 相似文献
243.
B. S. Kandemir 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):51-55
We study the effect of polaronic corrections arising from theelectron-longitudinal optical phonon interaction on the energyspectrum of a two-dimensional electron system with a one-dimensionalperiodic antidot array geometry created by a weak electrostaticmodulation potential, and subjected to a weak magnetic fieldmodulation as well as a uniform strong perpendicular staticmagnetic field. To incorporate the effects of electron-phononinteractions within the framework of Fröhlich polaron theory, wefirst apply a displaced-oscillator type unitary transformation todiagonalise the relevant Fröhlich Hamiltonian, and we thendetermine the parameters of this transformation together with theparameter included in the electronic trial wave function . On thebasis of this technique, it has been shown that the polaroniccorrections have non-negligible effects on the electronic spectrumof a two-dimensional electron system with a quantum antidot array,since switching such an interaction results in shifting thedegeneracy restoring points of Landau levels wherein the flatbandcondition is fulfilled, thus suppressing the Weiss oscillations. 相似文献
244.
M. Fally 《Applied physics. B, Lasers and optics》2002,75(4-5):405-426
Since its discovery in 1966, the photorefractive effect, i.e. the change of the refractive index upon illumination with light,
has been studied extensively in various materials and has turned out to play a key role in modern optical technologies like
photonics. This article focuses on substances that change their refractive index for neutrons when irradiated with light.
In analogy to light optics, we call them photo-neutronrefractive. After a short introduction to the relevant concepts of neutron
optics, two materials exhibiting this effect, a photopolymer and an electrooptic crystal, are presented. Further, we discuss
the progress made concerning the development of creating light-induced gratings for neutron diffraction, which culminated
in the setup of an interferometer for cold neutrons. Experiments performed on photo-neutronrefractive materials are surveyed
and the variety of corresponding results obtained is presented, including a discussion of their impact on material science,
neutron optics, and the foundations of physics.
Received: 23 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +43-1/4277-9511, E-mail: martin.fally@exp.univie.ac.at 相似文献
245.
The micromachining of hydroxyapatite (HAp) is highly important for orthopedics and dentistry, since human bone and teeth consist
mainly of HAp. We demonstrate ultrashort Ti:sapphire laser ablation of HAp, using pulse-widths of 50 fs, 500 fs, and 2 ps
at a wavelength of 820 nm and at 1 kpps. The crucial medical issue is to preserve the chemical properties of the machined
(ablated) surface. If the chemical properties of HAp change, the human bone or tooth cannot re-grow after laser processing.
Using X-ray photoelectron spectroscopy, we observe chemical properties of HAp ablated in air. The HAp is ablated at laser
fluences of 3.2 J/cm2 (6.4×1013 W/cm2 at 50 fs), 3.3 J/cm2 (6.6×1012 W/cm2 at 500 fs), and 9.6 J/cm2 (4.8×1012 W/cm2 at 2 ps), respectively. As a result it is found that the ablated surface is unchanged after laser ablation over the pulse-width
range used in this experiment.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-45/566-1533, E-mail: obara@obara.elec.keio.ac.jp 相似文献
246.
Takayuki Iwasaki Tasuku Maki Daisuke Yokoyama Hironori Kumagai Yasuhiro Hashimoto Takuma Asari Hiroshi Kawarada 《固体物理学:研究快报》2008,2(2):53-55
Vertically aligned double‐walled carbon nanotubes (DWCNTs) with the highest selectivity of 90% were synthesized by a controlled heating method and their electric double‐layer capacitor characteristics were evaluated. DWCNT arrays had a specific capacitance of 83 F/g, which is one of the highest values among CNT arrays in a nonaqueous solution and is almost equivalent to that for single‐walled CNT (SWCNT) arrays reported previously. At the same specific capacitance, DWCNTs with superior structural properties are more promising for practical capacitors than SWCNTs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
247.
Yuan Xu Wang 《固体物理学:研究快报》2008,2(3):126-128
Using density functional theory, the author predicts that the compounds ReC and TcC with the hexagonal WC‐like structure are ultra‐incompressible and hard materials. This is concluded from the very large bulk and shear moduli. The phonon dispersion reveals no soft modes indicating the stability of the two materials. The calculated density of states shows that ReC and TcC are metallic. The structural and elastic properties of OsC, IrC, and PtC with hexagonal and cubic structure are also investigated for comparison. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
248.
M. Sagmeister U. Brossmann E. J. W. List R. Ochs D. V. Szabó R. Würschum 《固体物理学:研究快报》2008,2(5):203-205
Stable suspensions of pentacene functionalised ZrO2 nano‐particles were synthesised using a microwave plasma process. The particles were dispersed in‐situ in ethylene glycol. The formation of coated particles with small cores and a well defined size in the range of 3–5 nm was shown by X‐ray diffraction. In difference to resublimed pure pentacene, suspensions of the coated nano‐particles remained stable for weeks, as confirmed by the observation of a small aggregate size in dynamic light scattering. Thin films of the particles on Si based substrates were obtained by drop‐casting. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
249.
Electrical characteristics of In0.05 Ga0.95N/Al0.07Ga0.9aN and In0.05 Ga0.95N/GaN multiple quantum well (MQW) ultraviolet light-emltting diodes (UV-LEDs) at 400hm wavelength are measured. It is found that for InGaN/AlGaN MQW LEDs, both ideality factor and parallel resistance are similar to those of InGaN/GaN MQW LEDs, while series resistance is two times larger. It is suggested that the Al0.07Ga0.93N barrier layer did not change crystal quality and electrical characteristic of p-n junction either, but brought larger series resistance. As a result, InGaN/AlGaN MQW LEDs suffer more serious thermal dissipation problem although they show higher light output efficiency. 相似文献
250.
U. Brossmann M. Sagmeister P. Pölt G. Kothleitner I. Letofsky‐Papst D. V. Szabó R. Würschum 《固体物理学:研究快报》2007,1(3):107-109
Nanocrystalline yttria‐stabilized zirconia (YSZ) powder and compacts have been successfully synthesized by microwave plasma synthesis co‐evaporating Y and Zr precursors from a single source. Both liquid and solid mixtures of chemically homologous precursors were tested. Electron micrographs and X‐ray diffraction studies reveal small crystallites in the range 3–4 nm with a narrow size distribution. Crystallite sizes smaller than 25 nm are preserved even after subsequent annealing at temperatures up to 950 °C. A comparison with other gas‐phase synthesis routes of nanocrystalline YSZ is given. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献