Colloids seeded deposition: growth of titania nanotubes in solution

The formation of titania nanotubes through CeO2 colloids seeded deposition process in solution has been demonstrated. The interactions among colloidal particles play important roles for the solution "VLS"-type growth of nanotubes. The observation has significance for understanding solution nucleation and for developing new methods for nanomaterials preparation via the disclosed colloids seeded deposition (CSD) mechanism.     

Resonant electron transfer and luminescent enhancement in a toluene suspension of Si nanocrystals

Efficient resonant electron transfer from the surface bonding structure to the conduction band of quantum confined Si nanocrystals is observed by Si nanocrystals in a toluene suspension. Based on the electron transfer mechanism, the enhancement of photoluminescence originates from the band-to-band recombination in the p-type Si nanocrystals suspended in a toluene solution. The energy levels of the electrons in the Si nanocrystals chemisorbed with toluene molecules are calculated using the method of linear combination of atomic orbitals, and the characteristics of the obtained density of states is in good agreement with the observed photoluminescence properties.     

Non-zwitterionic structures of aliphatic-only peptides mediated the formation and dissociation of gas phase radical cations

We have investigated how the non-zwitterionic and zwitterionic structures of aliphatic-only tripeptides affect the formation and dissociation of peptide radical cations in the gas phase. The non-zwitterionic forms of the aliphatic-only peptides in their metal complexes play an important role in determining whether the electron transfer pathway predominates. We extended this study by synthesizing permanent non-zwitterionic and zwitterionic forms of aliphatic-only peptide radical cations and exploring their reactivities in the gas phase. Collision-induced dissociation spectra demonstrated the feasibility of generating both non-zwitterionic and zwitterionic forms. Radical cations in zwitterionic forms may indeed mediate the beta and gamma carbon-carbon bond cleavages of leucine and isoleucine side chains from the GlyGlyXle radical peptides; this feature allows leucine and isoleucine residues to be distinguished unambiguously.     

Influence of electric field intensity, ionic strength, and migration distance on the mobility and diffusion in DNA surface electrophoresis

In order to increase the separation rate of surface electrophoresis while preserving the resolution for large DNA chains, e.g., genomic DNA, the mobility and diffusion of Lambda DNA chains adsorbed on flat silicon substrate under an applied electric field, as a function of migration distance, ionic strength, and field intensity, were studied using laser fluorescence microscope. The mobility was found to follow a power law with the field intensity beyond a certain threshold. The detected DNA peak width was shown to be constant with migration distance, slightly smaller with stronger field intensity, but significantly decreased with higher ionic strength. The molecular dynamics simulation demonstrated that the peak width was strongly related with the conformation of DNA chains adsorbed onto surface. The results also implied that there was no diffusion of DNA during migration on surface. Therefore, the Nernst-Einstein relation is not valid in the surface electrophoresis and the separation rate could be improved without losing resolution by decreasing separation distance, increasing buffer concentration, and field intensity. The results indicate the fast separation of genomic DNA chains by surface electrophoresis is possible.     

A sheath-flow nanoelectrospray interface of microchip electrophoresis MS for glycoprotein and glycopeptide analysis

Microchip was coupled with MS through a stable, sensitive, and controllable sheath-flow nanoelectrospray (nES) interface for glycoprotein and glycopeptide analysis. The nano-ESI (nESI) was made with a delivery capillary, a commercial nES capillary, and a stainless steel (SS) tube which were connected together through a tee unit. High voltage for nES was applied on the SS tube and the commercial nES capillary was used as nES emitter. The delivery capillary was attached to the microchannel for delivering liquid from microchip to the nESI source. The flow rate of sheath liquid was optimized to be 100-200 nL/min which largely reduced the sample dilution. The detection limit of peptides on this microchip/MS platform was at femtomole level. Glycoprotein and glycopeptides were also successfully analyzed on the platform. All the glycoforms and glycopeptides of ribonuclease B (RNase B) were identified with this method. Some structures of the glycopeptides from RNase B were further characterized with MS/MS on the microchip, coupled with a quadrupole IT-MS.     

A disk-pivot structure micro piezoelectric actuator using vibration mode B11

Micro piezoelectric actuator using vibration mode B(11) (B(mn), where m is the number of nodal circles, n is the nodal diameters) is designed. Different from conventional wobble-type ultrasonic motor using piezoelectric rod or cylinder, piezoelectric disc is used to excite wobble modes and metal cylinder stator is used to amplify the transverse displacement, metal rod rotor is actuated to rotate. The outer diameter of the actuator is 14mm. There are features such as low drive voltage, micromation, and convenient control of wobble state by modifying the structure of stator, etc. Finite element analysis (FEA) of the stator has been made. It is found that the resonant frequency of vibration mode B(11) is 49.03kHz, which is measured at 45.7kHz by the laser vibrometer and impedance analyzer. The rotation speed has been measured, which could be as high as 10,071rpm under an alternating current 100V. Such piezoelectric actuator can be optimized and adjusted to fit practical conditions. It can be applied in the fields of precise instrument, bioengineering and other micro actuator system.     

Phase-locked, low-noise, frequency agile titanium:sapphire lasers for simultaneous atom interferometers

We demonstrate a laser system consisting of a >1.6 W titanium:sapphire laser that is phase locked to another free-running titanium:sapphire laser at a wavelength of 852 nm with a phase noise of -138 dBc/Hz at 1 MHz from the carrier, using an intracavity electro-optic phase modulator. The residual phase variance is 2.5 x 10(-8) rad2 integrated from 1 Hz to 10 kHz. This system can phase-continuously change the offset frequency within 200 ns with frequency steps up to 4 MHz. Simultaneous atom interferometers can make full use of this ultralow phase noise in differential measurements, where influences from the vibration of optics are greatly suppressed in common mode.     

The geometric pattern of a pillared substrate influences the cell-process distribution and shapes of fibroblasts

Fibroblasts alter their shape, direction of movement, cytoskeleton arrangement, and focal contact when placed upon square array pillars. We prepared pillars of 1 μm diameter, separated by 3 μm, and having 1, 5, and 10 μm heights using substrates displaying identical surface chemistry. When cells seeded initially onto the tops of the pillars, fibroblasts subsequently were immobilized in situ by several pillars that visibly protruded through, but did not pierce, the cell bodies. The cytoplasma then migrated outward with long straight lamella along the interval of the pillars and formed several discrete attachment zones at their side walls – the value of their form index (FI) was as high as 35 – which altered the cellular shape entirely. Most of the cells interacted with the pillar substrate by spreading preferentially in a particular direction, but some of them had the ability to undergo coincident two-direction (x and y) migration; right-angle turn orientations led to the growth of dramatic cellular morphologies. Interestingly, this fibroblast's behavior variation was gradually in proportion to the pillar height of substrate. Our results confirm that cellular migration and cellular shape are both strongly affected by the geometry of the growth microenvironment.     

采用可见/近红外光谱检测大麦叶片过氧化氢酶与过氧化物酶含量的研究

采用可见/近红外光谱对丙酯草醚胁迫下大麦叶片过氧化氢酶(catalase, CAT)与过氧化物酶(peroxidase, POD)含量预测进行研究。对500～900 nm光谱采用移动平均法(moving average, MA)11点平滑方法进行预处理。采用蒙特卡罗-偏最小二乘法(monte carlo-partial least squares, MCPLS)方法分别对于CAT与POD的含量预测剔除7个与8个异常样本。基于全部光谱建立了CAT与POD含量预测的PLS,最小二乘支持向量机(least-squares support vector machine, LS-SVM)与极限学习机(extreme learning machine, ELM)模型,ELM模型对CAT含量预测效果最好,建模集相关系数(correlation coefficient of calibration, R_c)为0.916,预测集相关系数R_p为0.786;PLS模型对POD含量预测效果最佳,R_c为0.984,R_p为0.876。采用连续投影算法(successive projections algorithm, SPA)算法分别为CAT与POD预测选择了8个与19个特征波长,基于特征波长建立的PLS,LS-SVM与ELM模型中,ELM模型对CAT与POD含量预测效果均最佳,CAT含量预测的相关系数为R_c=0.928,R_p=0.790;POD含量预测的相关系数R_c=0.965,R_p=0.941。基于全谱与基于特征波长的回归分析模型预测效果相当,且对POD含量的预测效果优于对CAT含量的预测效果,而这需要进一步研究以得到精度和稳定性更高的预测模型。研究结果表明,采用可见/近红外光谱结合化学计量学方法可以实现对除草剂胁迫下大麦叶片CAT与POD含量的预测。     

近地高光谱成像技术对黑豆品种无损鉴别

基于近地高光谱成像技术结合化学计量学方法,实现了黑豆品种的鉴别。实验以三种不同颜色豆芯的黑豆为研究对象,采用高光谱成像系统采集380～1 030 nm波段范围的高光谱图像,提取高光谱图像中的样本感兴趣区域平均光谱信息作为样本的光谱进行分析,建立黑豆品种的判别分析模型。共采集180个黑豆样本的180条平均光谱曲线。剔除明显噪声部分之后以440～943 nm范围光谱为黑豆样本的光谱,采用多元散射校正(multiplicative scatter correction,MSC)对光谱曲线进行预处理。分别以全部光谱数据、主成分分析(principal component analysis,PCA)提取的光谱特征信息、小波分析(wavelet transform,WT)提取的光谱特征信息建立了偏最小二乘判别分析法(partial least squares discriminant analysis,PLS-DA),簇类独立模式识别法(soft independent modeling of class analogy,SIMCA),最邻近节点算法(K-nearest neighbor algorithm,KNN),支持向量机(support vector machine,SVM), 极限学习机(extreme learning machine,ELM)等判别分析模型。以全谱的判别分析模型中,ELM模型效果最优;以PCA提取的光谱特征信息建立的模型中,ELM模型也取得了最优的效果;以WT提取的光谱特征信息建立的模型中,ELM模型结识别效果最好,建模集和预测集识别正确率达到100%。在所有的判别分析模型中,WT-ELM模型取得了最优的识别效果。实验结果表明以高光谱成像技术对黑豆品种进行无损鉴别是可行的,且WT用于提取光谱特征信息以及ELM模型用于判别黑豆品种能取得较好的效果。