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941.
942.
943.
Proper identification of proteinaceous binders in artworks is essential for specification of the painting technique and thus
also for selection of the restoration method; moreover, it might be helpful for the authentication of the artwork. This paper
is concerned with the optimisation of analysis of the proteinaceous binders contained in the colour layers of artworks. Within
this study, we worked out a method for the preparation and analysis of solid samples from artworks using tryptic cleavage
and subsequent analysis of the acquired peptide mixture by matrix-assisted laser desorption/ionisation time of flight mass
spectrometry. To make this approach rational and efficient, we created a database of commonly used binders (egg yolk, egg
white, casein, milk, curd, whey, gelatine, and various types of animal glues); certain peaks in the mass spectra of these
binders, formed by rich protein mixtures, were matched to amino acid sequences of the individual proteins that were found
in the Internet database ExPASy; their cleavage was simulated by the program Mass-2.0-alpha4. The method developed was tested
on model samples of ground layers prepared by an independent laboratory and then successfully applied to a real sample originating
from a painting by Edvard Munch. 相似文献
944.
All-dielectric nanoparticles, as the counterpart of metallic nanostructures have recently attracted significant interest in manipulating light-matter interaction at a nanoscale. Directional scattering, as an important property of nanoparticles, has been investigated in traditional high refractive index materials, such as silicon, germanium and gallium arsenide in a narrow band range. Here in this paper, we demonstrate that a broadband forward scattering across the entire visible range can be achieved by the low loss TiO2 nanoparticles with moderate refractive index. This mainly stems from the optical interferences between the broadband electric dipole and the magnetic dipole modes. The forward/backward scattering ratio reaches maximum value at the wavelengths satisfying the first Kerker’s condition. Experimentally, the femtosecond pulsed laser was employed to splash different-sized nanoparticles from a thin TiO2 film deposited on the glass substrate. Single particle scattering measurement in both the forward and backward direction was performed by a homemade confocal microscopic system, demonstrating the broadband forward scattering feature. Our research holds great promise for many applications such as light harvesting, photodetection and on-chip photonic devices and so on. 相似文献
945.
设计并优化了一种用808nm的大功率激光二极管为抽运光源,In0.09Ga0.91As量子阱结构为增益介质的920nm光抽运半导体垂直外腔面发射激光器。运用有限元方法,对激光器的电特性方程和光特性方程求自洽解,计算了器件各种特性参量。分析了单个周期内不同阱的个数(1,2和3)、不同阱深、不同垒宽、不同非吸收层组分、不同非吸收层尺寸条件下,器件性能的改变,特别是模式、阈值和光-光转换效率的改变,从而选择一个最佳的结构。 相似文献
946.
The mechanism of femtosecond optical pulse generation in a self-starting Er3+-doped fiber ring soliton laser and experimental research results are discussed. Using the nonlinear polarization rotation
effect of the fiber for sat-urable absorbers (and then self-amplitude modulation) which acts as the mode locking mechanism
in an Er3+-doped fiber ring cavity laser, stable self-starting mode locking pulses have been generated. The shortest output pulse is
269 fs, with the central wavelength of 1,531 pm at the repetition rate of 21.37 MHz. The average output powen of the two terminators
of the laser are 0.25 mW and 0.08 mW respectively. The threshold pump power which sustains the mode locking is 15 mW. Under
high pump power, the laser works in a high order harmonic mode locking state. The mode locking pulse durations vs different
cavity lengths are also studied.
Project supported by Major Project of Chines: Academy of Sciences (No. KJ952-J1-705). 相似文献
947.
Hye Jin Lee Paul D. Beattie Brian J. Seddon Murray D. Osborne Hubert H. Girault 《Journal of Electroanalytical Chemistry》1997,440(1-2)
A polymer membrane for the selective amperometric transfer and sensing of molecular ions has been designed and characterised. The membrane was formed from two polymer layers, a supporting film of polyethylene terephthalate on which an electrolyte film containing polyvinylchloride is cast. The polyester layer has a laser-etched pattern of circular micro-holes in one region. These hole structures are arranged in a rectangular geometry and measure 22 μm in diameter with separation distances of 105 μm and 120 μm. The polyvinylchloride underlayer is a composite system comprised of a 2-nitrophenyl octyl ether plasticising solution containing an electrolytic salt of tetrabutylammonium tetrakts-(4-chlorophenyl)borate. In this way, an array of micro-interfaces between an analyte solution and a PVC gel electrolyte is formed and used as a liquid|liquid interface for the amperometric monitoring of ion transfer reactions. The membrane was characterised in terms of the voltammetric response to choline transfer. The study includes an examination of the fabrication methodology, materials composition and membrane structure. 相似文献
948.
949.
利用修改的一维非定态程序,基于美国杰弗逊实验室(JLab)Demo自由电子激光装置的参数,对高功率自由电子激光振荡器稳定波长的反馈系统进行了数值模拟。电子微脉冲为高斯型分布,每个纵向网格中取16个模拟宏电子,不考虑电子束的能散度。结果表明:当无反馈时,腔内光功率和波长都可以在一定范围内稳定;加入反馈后,由于电子束能量的变化所引起的等效失谐对整个系统有着重要的影响,甚至可能导致电子和光场失去相互作用,从而使得装置不能工作。提出应该在光场达到饱和以后再启动稳定波长反馈系统。模拟结果证明,该实施方案是合理有效的,可以避免其对FEL运行的严重影响。 相似文献
950.
研制了一台高效率全固态平均功率7.13 W的1 319 nm宏微脉冲激光器。激光器采用热稳Z形折叠腔,增益模块采用自行研制的准连续15个二极管芯片环形泵浦的Nd:YAG模块,采用主动声光锁模器作为锁模元件,并在腔内插入倍频KTP晶体对激光器的输出尖峰进行抑制。为了获得稳定的锁模状态,对激光器腔长进行了精确设计和调节。当激光器腔长与锁模器驱动频率匹配时,获取了宏脉冲重复频率400 Hz、脉宽约190 μs,微脉冲重复频率95.6 MHz、脉宽小于1.0 ns的1 319 nm激光脉冲。 相似文献