一种提高共聚焦显微镜信噪比算法的研究

基于共焦显微镜的成像特点,建立了Kalman滤波算法的理论模型,把Kalman滤波方法引入到系统中,提出一种基于图像像素的Kalman滤波算法,并实现了实时化的Kalman滤波器。实验结果表明:该算法能够有效地提高共焦显微镜信噪比,但是以牺牲时间为代价,提高系统分辨率的根本方法还是要着重考虑优化成像系统光路和探测电路。     

用劈尖干涉测金属线胀系数

文中结合劈尖干涉原理和金属线胀系数计算公式,通过测量受热前后黄铜丝直径的微小变化,导出黄铜丝的线胀系数．实验取得良好效果。     

Final state effect for Au 4f line from gold-nano-particles grown on oxides and HOPG supports

The effect of a positive charge left to a small metal particle immediately after photoemission, so called the final state effect is studied for Au 4f binding energy (E_B) shifts. The size and shape of Au nano-particles were determined by high-resolution medium energy ion scattering combined with scanning electron microscopy of a field emission type. The shape of Au nano-particles is well approximated by a partial sphere with diameter d and height h. It is found that the E_B shift is well expressed as number of atoms per particle (n_A) and independent of support species. The E_B shift changes dramatically at a critical n_A value of ∼70 atoms, where metal-nonmetal transition takes place. In the nonmetal region, the E_B shift increases steeply almost exponentially with decreasing n_A and in contrast, gradually decreases with increasing n_A in the metallic region. The effect of the positive charge of an Au 4f vacancy created by photoemission is expressed by the relaxation time τ and the effective charge +αe when the photoelectron just leaves the Au particle surface (e: electron charge, α < 1).     

First observation of natural circular dichroism spectra in the extreme ultraviolet region using a polarizing undulator‐based optical system and its polarization characteristics

Natural circular dichroism (CD) spectra in the extreme ultraviolet (EUV) region down to a wavelength of 80 nm have been observed for the first time, using an alanine thin film deposited on sodium salicylate coated glass as a sample. Calibrated EUV‐CD spectra of l ‐alanine exhibited a large negative peak at around 120 nm and a positive CD signal below 90 nm, which were roughly predicted by theoretical calculations. A CD measurement system with an Onuki‐type polarizing undulator was used to obtain the EUV‐CD spectra. This CD system, the development of which took five years, can be used to observe even weak natural CD spectra. The polarization characteristics of this system were also evaluated in order to calibrate the recorded CD spectra.     

Nucleosome Dynamics as Studied by Single-pair Fluorescence Resonance Energy Transfer: A Reevaluation

Accessibility of nucleosomal DNA to protein factor binding is ensured by at least three mechanisms: post-synthetic modifications to the histones, chromatin remodeling, and spontaneous unwrapping of the DNA from the histone core. We have previously used single-pair fluorescence resonance energy transfer (spFRET) experiments to investigate long-range conformational fluctuations in nucleosomal DNA (Tomschik M, Zheng H, van Holde K, Zlatanova J, Leuba SH in Proc Natl Acad Sci USA 102(9):3278–3283, 2005). Recent work has drawn attention to a major artifact in such studies due to photoblinking of the acceptor fluorophore. We have now used formaldehyde-crosslinked nucleosomes and imaging in the presence of Trolox, an efficient triplet-state quencher that suppresses photoblinking, to reevaluate our previous conclusions. Careful analysis of the data indicates that most of the events previously characterized as nucleosome ‘opening’ must have corresponded to photoblinking. There is, nevertheless, evidence for the existence of infrequent, rapid opening events.     

Characterization of InN epilayers grown on Si(1 1 1) substrates at various temperatures by MBE

InN films have been grown by plasma-assisted molecular beam epitaxy (PAMBE) and characterized by various technologies. It was found that the structural, optical and electrical properties can be drastically improved by raising growth temperature from 440 to 525 °C. Grainy morphology was found in the grain size was found in atomic force microscope images. The large grain size was about 360 nm for a film grown at 525 °C. These films exhibited Wurtzite structure with a c/a ratio ranging from 1.59 to 1.609. The dislocation densities estimated by X-ray diffraction techniques closely agreed with those analyzed by plan-view transmission electron microscopy. Photoluminescence (PL) studies confirmed near band-to-band transitions and the narrowest low-temperature PL peak width was found to be 24 meV at 0.666 eV. Carrier concentrations decreased from 1.44×10¹⁹ to 1.66×10¹⁸ cm⁻³ and Hall mobility increased from 226 to 946 cm² V⁻¹ s⁻¹ as the growth temperature is progressively increased from 440 to 525 °C. Raman spectra also indicated improved crystal quality as the growth temperature was raised.     

Raman spectroscopy of automotive paints: Forensic analysis of variability and spectral quality

Raman spectroscopy was evaluated as a forensic technique for the analysis of automotive paints with the purpose to verify the measurement variability as well as to study the spectral quality by means of parameters and conditions. The objective lens, accumulation number, and laser (power, mode, and wavelength) were observed to significantly affect the spectral quality and thus should be taken into consideration during the development of a forensic database. On the other hand, exposure time, Raman shift range, and baseline correction had less influence on the features of the obtained spectra. Interestingly, samples collected from the bumper coating composed of a plastic substrate in comparison with fragments obtained from other parts of the same vehicle containing metallic substrate showed different absorption band patterns. In addition, less variability of data acquired directly onto the paint chip’s surface has demonstrated that direct analysis should be preferred during spectra library development as opposed to cross-section measurements. Sample homogeneity and distinction power of the technique combined with Principal Components Analysis were also investigated. The preliminary results showed that although Raman spectroscopy is extremely accurate in the identification of vehicles, it is necessary to pay particular attention to the spectral variability in order to avoid false database matching and misleading of forensic investigations. Therefore, we suggest that separated spectra library shall be developed for each laser wavelength as well as for each sample substrate. Further studies with a higher number of paint chips will enable the establishment of prediction models aimed to identify unknown samples involved in hit-and-run cases.     

Ion‐Beam Sculpting of Nanowires

Nanomaterials often undergo unusual mechanical deformations compared to their bulk counterparts when irradiated with ion‐beams. This study visualizes and investigates some of the unusual interactions that can occur in nanomaterials during irradiation with medium‐energy ion‐beams using a helium‐ion microscope (HIM). Ion‐beam sculpting of semiconductor nanowires (NWs) with sub‐10 nm features is demonstrated. Moreover, irradiation‐induced growth of NWs at room‐temperature is discovered. The new concept and possible mechanism of irradiation‐induced VLS (vapor–liquid–solid) growth of NWs is introduced. These results are the basis for further fundamental and technological developments toward manipulation and visualization of ion–matter interactions at the nanoscale.     

Precise autofocusing microscope with rapid response

The rapid on-line or off-line automated vision inspection is a critical operation in the manufacturing fields. Accordingly, this present study designs and characterizes a novel precise optics-based autofocusing microscope with a rapid response and no reduction in the focusing accuracy. In contrast to conventional optics-based autofocusing microscopes with centroid method, the proposed microscope comprises a high-speed rotating optical diffuser in which the variation of the image centroid position is reduced and consequently the focusing response is improved. The proposed microscope is characterized and verified experimentally using a laboratory-built prototype. The experimental results show that compared to conventional optics-based autofocusing microscopes, the proposed microscope achieves a more rapid response with no reduction in the focusing accuracy. Consequently, the proposed microscope represents another solution for both existing and emerging industrial applications of automated vision inspection.     

Characterisation and mesomorphic behaviour of liquid crystals with dispersed PdCl2 nanoparticles

The synthesis and characterisation are carried on liquid crystalline (LC) p-dodecyloxy benzoic acid (12OBA) with 1 and 2 wt% for PdCl₂ nanoparticles dispersion. Further, characterizations are carried out by different spectroscopic techniques like X-ray diffraction spectrometric studies, scanning electron microscopy, Fourier transform infrared and differential scanning calorimetry (DSC). Textural determinations of the synthesised compounds are recorded by using polarising optical microscope (POM) attached with a hot stage and camera. The results show that the dispersion of PdCl₂ nanoparticles in 12OBA exhibits Nematic phases as same as the pure 12OBA with reduced clearing temperature as expected. Further, the nematic thermal ranges are quenched and the smectic C thermal range has been increased while performing both DSC and POM with the dispersion of 1 wt% PdCl₂ nanoparticles. Size dependence on bonding nature with LC compounds is established.