Micromachining NiTi tubes for use in medical devices by using a femtosecond laser

Recent growth in medical device technology has been substantially driven by developments in laser micromachining, which is a powerful fabrication technique in which nickel–titanium (Nitinol, NiTi) alloy materials that exhibit superelastic and shape memory properties are formed (e.g., self-expanding stents). In this study a NiTi tube curve surface process is proposed, involving a femtosecond laser process and a galvano-mirror scanner. The diameter of the NiTi tube was 5.116 mm, its thickness was 0.234 mm, and its length was 100 mm. The results indicated that during the machine process the ablation mechanism of the NiTi tubes was changed by altering the machining path. The path alteration enhanced the laser ablation rate from 12.3 to 26.7 μm/J. Thus the path alteration contributed to a wide kerf line, enabling the assisted air to efficiently remove the debris deposited at the bottom of the kerf during the laser ablation process. The results indicated that the NiTi tube curve process enhanced the laser ablation rate by two times and reduced the amount of energy accumulated within the materials by 50% or more. By altering the machining path using the scanning system, this process can decrease the production of heat affected zones (the accumulation of thermal energy) in medical device applications.     

The fully digital evaluation of photographic PIV recordings

The performance of a purely digital evaluation system for photographic PIV recordings is described. High resolution digital images are obtained from the 35 mm negatives using a commonly available slide scanner. Together with the continually improving capabilities of standard computers, this evaluation system is a cost effective alternative to the traditional analog optical/digital (Young's fringe method) and purely optical PIV interrogation systems. Compared to the optical systems the fully digital evaluation can provide a higher spatial resolution while maintaining a similar measurement uncertainty. Using actual PIV recordings absolute measurement uncertainties are obtained and further predictions toward optimal displacement data recovery are made with the aid of Monte-Carlo simulations. Measurement uncertainties are minimized for particle image diameters on the order of 2 pixels while the reduction of the image depth (i.e. bits/pixel) has little effect. The overall performance of the described digital evaluation is compared to two types of optical evaluation systems.Affiliated with DNW-NWB, DLR-Braunschweig.     

Aptamer‐based thrombin assay on microfluidic platform

A facile and sensitive aptamer‐based protocol has been developed for protein assay on microfluidic platform with fluorescence detection using an off‐chip microarray scanner. Aptamer‐functionalized magnetic beads were used to capture thrombin that binds to a second aptamer fluorescently labeled by Cy3. Experimental conditions, such as incubation time and temperature, washing time, interfering proteins, and aptamer, etc., were optimized for the microchip method. This work demonstrated there was a good relationship between fluorescence intensity and thrombin concentration in the range of 65–1000 ng/mL with the RSD less than 8%. Notably, an analysis only needs 1 μL volume of sample injection and this system can capture extremely tiny amount thrombin (0.4 fmol). This method has been successfully applied to assay of thrombin in human serum with the recovery of 79.74–95.94%.     

A High-Speed 12-Layer Two-Dimensional Bar-Code Detection System

A new photodetection amplifier configuration with an amplification-type current-to-voltage converter is presented to realize a high-gain wideband amplifier. A high-speed 12-layer two-dimensional (2D) bar-code detection system (BCDS), consisting of the new photodetection amplifier and a raster scanner combined with a complementary light emission drive method for laser diodes, has been developed to provide both a highly effective scanning speed and multi-layer bar-code detection. The 12-layer 2D BCDS has shown 1,250 scan/s, which is two and a half times the scanning speed of a conventional bar-code detection system. Comparison with experimental results verified that Li’s scan pattern theory provides an accurate model for laser scanning beam traces obtained by the raster scanner. As theoretical evaluation of bar-code configuration in the new system, an optimum bar-code height per one-layer is given by a function of detection length.     

The class of microarray games and the relevance index for genes

Nowadays, microarray technology is available to generate a huge amount of information on gene expression. This information must be statistically processed and analyzed, in particular, to identify those genes which are useful for the diagnosis and prognosis of specific diseases. We discuss the possibility of applying game-theoretical tools, like the Shapley value, to the analysis of gene expression data. Via a “truncation” technique, we build a coalitional game whose aim is to stress the relevance (“sufficiency”) of groups of genes for the specific disease we are interested in. The Shapley value of this game is used to select those genes which deserve further investigation. To justify the use of the Shapley value in this context, we axiomatically characterize it using properties with a genetic interpretation. The authors are grateful to two anonymous referees for their extremely helpful comments. An earlier version of this paper was presented at the VI Spanish Meeting on Game Theory and Practice, July 12–14, 2004, Elche, Spain. S. Moretti gratefully acknowledges the financial support of the EU project NewGeneris, European Union 6th FP (FOOD-CT-2005-016320).     

Method for measuring integrated sensitivity of solar cells and multielement photoconverters using an X-Y scanner

We describe a method for automated measurement of the integrated sensitivity of solar cells (SCs) and multielement photoconverters (MPCs) using an experimental apparatus including a Pentium III personal computer (PC), an HP-34401A digital multimeter (DM), a stabilized radiation source (SRS), a controllable focusing system, an X-Y positioning device based on CD-RW optical disk storage devices. The method provides high accuracy in measuring the size of photosensitive areas of the solar cells and multielement photoconverters and inhomogeneities in their active regions, which makes it possible to correct the production process in the development stage and during fabrication of test prototypes for the solar cells and multielement photoconverters. The radiation power from the stabilized radiation source was ≤1 W; the ranges of the scanning steps along the X, Y coordinates were 10–100 μm, the range of the transverse cross sectional diameters of the focused radiation beam was 10–100 μm, the measurable photocurrents were 10⁻⁹ A to 2 A; scanning rate along the X, Y coordinates, ≤100 mm/sec; relative mean-square error (RMSE) for measurement of the integrated sensitivity of the solar cells, 0.2 ≤ γS _int ≤ 0.9% in the ranges of measurable photocurrents 1 mA ≤ I_ph ≤ 750 mA and areas 0.1 ≤ A ≤ 25 cm² for number of measurements equal to ≤ 2· 10⁵; instability of the radiation power (luminosity) ≤ 0.08% for 1 h or ≤ 0.4% for 8 h continuous operation; stabilized power range for the stabilized radiation source, 10⁻²–10² W. The software was written in Delphi 7.0. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 670–675, September–October, 2006.     

多面体扫描电弧成象仪

交流喷口电弧瞬态温度实时测量是目前高压电器领域里的一个难题。要深入研究高压输电线路中的气吹断路器灭弧机理,必然要涉及到在极短时间内测量电弧等离子体温度变化问题。电弧等离子体是一种高温电离气体,它辐射出丰富的光谱信息。采用光谱法测量是合适的。转镜式电弧成象仪正是为实现上述测量而研制的专用设备。它与光栅光谱仪、高速数据采集系统、微机等构成一套完整的电弧光谱温度测量系统。本文论述了该设备的总体方案、设计特色、整机性能指标。     

A novel clustering approach and prediction of optimal number of clusters: global optimum search with enhanced positioning

Cluster analysis of genome-wide expression data from DNA microarray hybridization studies is a useful tool for identifying biologically relevant gene groupings (DeRisi et al. 1997; Weiler et al. 1997). It is hence important to apply a rigorous yet intuitive clustering algorithm to uncover these genomic relationships. In this study, we describe a novel clustering algorithm framework based on a variant of the Generalized Benders Decomposition, denoted as the Global Optimum Search (Floudas et al. 1989; Floudas 1995), which includes a procedure to determine the optimal number of clusters to be used. The approach involves a pre-clustering of data points to define an initial number of clusters and the iterative solution of a Linear Programming problem (the primal problem) and a Mixed-Integer Linear Programming problem (the master problem), that are derived from a Mixed Integer Nonlinear Programming problem formulation. Badly placed data points are removed to form new clusters, thus ensuring tight groupings amongst the data points and incrementing the number of clusters until the optimum number is reached. We apply the proposed clustering algorithm to experimental DNA microarray data centered on the Ras signaling pathway in the yeast Saccharomyces cerevisiae and compare the results to that obtained with some commonly used clustering algorithms. Our algorithm compares favorably against these algorithms in the aspects of intra-cluster similarity and inter-cluster dissimilarity, often considered two key tenets of clustering. Furthermore, our algorithm can predict the optimal number of clusters, and the biological coherence of the predicted clusters is analyzed through gene ontology.     

HT—6B装置离子温度的光谱法测定

一、引言 在托卡马克高温等离子体诊断中,离子温度T_i是表征等离子体的重要参数之一,对定量了解等离子体内部的信息是非常有用的。它对能量输运、能量平衡和加热机制的研究都是必不可少的。     

Microcontact printing of Alzheimer’s β-amyloid monomers and fibrils

Adsorption of the 40-residue Alzheimer’s β-amyloid peptide (Aβ40) on a hydrophobic surface leads to formation of potentially disease-relevant aggregates. Existing techniques are limited in characterizing the adsorbed Aβ40 and producing potentially useful Aβ40 microstructures such as microarrays and microparticles. In this paper, a novel approach based on microcontact printing (μCP) to studying and utilizing adsorption of Aβ40 monomers and fibril fragments on hydrophobic surface of polydimethylsiloxane (PDMS) stamps has been developed. By transferring the adsorbed layer from the stamp to a glass substrate, this approach allows easy measurement of thickness of the adsorbed layer. It also enables characterization of the face of the adsorbed layer in contact with the stamp surface. This face exhibits significant higher thioflavin T fluorescence than the face exposed to water, suggesting β-sheet formation induced by the PDMS surface. The intrinsic stability of the adsorbed layer is evaluated by printing the layer on a water-soluble substrate and exposing it to water vapor or water. Stable particulate microstructures in water are obtained by chemically crosslinking the adsorbed peptides. Moreover, co-micropatterning of the different states of Aβ40 (monomers and fibril fragments) is demonstrated. This μCP-based approach is simple, versatile, and holds potential for various applications.