Integrated light collimating system for extended optical-path-length absorbance detection in microchip-based capillary electrophoresis

We have developed an integrated light collimating system with a microlens and a pair of slits for extended optical path length absorbance detection in a capillary electrophoresis (CE) microchip. The collimating system is made of the same material as the chip, poly(dimethylsiloxane) (PDMS), and it is integrated into the chip during the molding of the CE microchannels. In this microchip, the centers of an extended 500-microm detection cell and two optical fibers are self-aligned, and a planoconvex microlens (r = 50 microm) for light collimation is placed in front of a light-delivering fiber. To block stray light, two rectangular apertures, realized by a specially designed three-dimensional microchannel, are made on each end of the detection cell. In comparison to conventional extended detection cell having no collimator, the percentage of stray radiation readout fraction in the collimator integrated detection cell is significantly reduced from 31.6 to 3.8%. The effective optical path length is increased from 324 to 460 microm in the collimator integrated detection cell. The detection sensitivity is increased by 10 times in the newly developed absorbance detection cell as compared to an unextended, 50-microm-long detection cell. The concentration detection limit (S/N = 3) for fluorescein in the collimator integrated detection cell is 1.2 microM at the absorbance detection limit of 0.001 AU.     

Studies on interaction of Nd3+ — Glass laser light with armco-Fe high pressure nitrogen medium

Some effects of the interaction of Nd³⁺-glass laser, working in ordinary generation regime, with Armco-Fe surrounded by nitrogen in the pressure range (1–109) atm. have been investigated. Thephenomenon of capillary waves and the increase of the N₂ content have been observed in the irradiated area. The mechanism of the laser light interaction with the metal is discussed in terms of plasma theory and X-ray analysis.     

Electrospray ionization with a pointed carbon fiber emitter

A new type of electrospray ionization emitter employing a pointed carbon fiber has been developed for interfacing nanoliquid sampling techniques to mass spectrometry. The pointed carbon fiber protruding from an orifice with a surrounding hydrophobic surface confines a small Taylor cone at the tip, which generates a stable electrospray at the tip point. The small Taylor cone improves the electrospray efficiency thereby enhancing the detection limit. This emitter is rugged and able to generate stable electrospray over a wide range of flow rate, ESI voltage, and surface tension variation. Using a solution of angiotensin I, the carbon fiber emitter in 75-microm-i.d. fused-silica tubing was shown to give ion current comparable to that from a commercial 8 microm orifice nanospray emitter. Use of the emitter for ESI-MS/MS analysis of peptides was examined by infusing a mixture of cytochrome c and myoglobin tryptic digest peptides. Protein identification was demonstrated at the level of less than 1 fmol of the peptide consumed. The use of the carbon fiber emitter for interfacing monolithic capillary HPLC to MS was also demonstrated.     

Heterogeneity assessment in individual CaCO3-CaSO4 particles using ultrathin window electron probe X-ray microanalysis

In our previous studies, it has been demonstrated that both the excitation interactions between electrons and the atoms of the matrix and the matrix and geometric effects of electron-induced X-ray signals can be described by Monte Carlo simulation for low-Z elements, such as carbon, nitrogen, and oxygen, in individual atmospheric microparticles. In addition, by the application of a quantification method, which employs Monte Carlo simulation combined with successive approximations, at least semi-quantitative specification of the chemical compositions could be done. This has enlarged the scope of electron probe X-ray microanalysis (EPMA) for the single particle analysis of atmospheric environmental aerosol particles. In this work, we demonstrate that the heterogeneity of individual particles, even of micrometer size, can be characterized by the application of EPMA. X-ray photons obtained with different primary electron beam energies carry information on the chemical compositions for different regions in the particles. Artificially generated heterogeneous CaCO3-CaSO4 individual particles were measured at different accelerating voltages, and it was found that the Monte Carlo calculation is a powerful technique to extract the information on the heterogeneity of the particles that is contained in the measured X-ray data. Our approach can even estimate the thickness of the surface CaSO4 species by the application of the Monte Carlo calculation. A preliminary result for carbon-coated glass particles is also presented. The complexity involved in the analysis of real world particles is briefly mentioned with a result for heterogeneous SiO2 particle.     

Design and evaluation of a hierarchical decoupled architecture

The speed gap between processor and main memory is the major performance bottleneck of modern computer systems. As a result, today's microprocessors suffer from frequent cache misses and lose many CPU cycles due to pipeline stalling. Although traditional data prefetching methods considerably reduce the number of cache misses, most of them strongly rely on the predictability for future accesses and often fail when memory accesses do not contain much locality. To solve the long latency problem of current memory systems, this paper presents the design and evaluation of our high-performance decoupled architecture, the HiDISC (Hierarchical Decoupled Instruction Stream Computer). The motivation for the design originated from the traditional decoupled architecture concept and its limits. The HiDISC approach implements an additional prefetching processor on top of a traditional access/execute architecture. Our design aims at providing low memory access latency by separating and decoupling otherwise sequential pieces of code into three streams and executing each stream on three dedicated processors. The three streams act in concert to mask the long access latencies by providing the necessary data to the upper level on time. This is achieved by separating the access-related instructions from the main computation and running them early enough on the two dedicated processors. Detailed hardware design and performance evaluation are performed with development of an architectural simulator and compiling tools. Our performance results show that the proposed HiDISC model reduces 19.7% of the cache misses and improves the overall IPC (Instructions Per Cycle) by 15.8%. With a slower memory model assuming 200 CPU cycles as memory access latency, our HiDISC improves the performance by 17.2%.     

颅脑损伤治疗仪的研究

本项研究是一种高氧低温式颅脑损伤治疗仪.它设有颅脑罩,颅脑罩扣合在底板上,颅脑罩上分别设置有与其内腔相通的进氧口,进冷口及阀门.制氧由电子制氧机制氧充入颅脑罩内,低温由晶体管降温技术降温,使罩内温度降至4℃左右.本仪器是在计算机控制下,使罩内达到高氧低温.在此环境内,能够对伤者头部进行均匀供氧并保持低温状态,使之达到治疗目的.它的特点是操作简单,治疗效果好,治疗费用低.     

Mechanical properties of Ir-Nb alloys containing Ni and Al

Two alloys made by adding 5 or 10 at. pct, respectively, of Ni-18.9 at. pct Al to an Ir-15 at. pct Nb alloy were investigated. The microstructure and compressive strength at temperatures between room temperature and 1800 °C were investigated to evaluate the potential of these alloys for ultra-high-temperature use. Their microstructural evolution indicated that the two alloys formed fcc and L1₂-Ir₃Nb two-phase structures. The fcc and L1₂ two-phase structures were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The 0.2 pct flow stresses were above 1000 MPa at temperatures up to 1200 °C, about 150 MPa at 1500 °C, and over 100 MPa at 1800 °C. The strength of the quaternary Ir-base alloys at 1200 °C was even higher than that of Ir-base binary and ternary alloys. And the strength of quaternary Ir-Nb-Ni-Al was equivalent to that of the Ir-15 at. pct Nb binary alloy at 1800 °C. The compressive ductility of quaternary (around 20 pct) was improved drastically compared with that of the Ir-base binary alloy (lower than 10 pct) and the ternary Ir-base alloys (about 11 pct). An excellent balance of high-temperature strength and ductility was obtained in the alloy with 10 at. pct Ni-18.9 at. pct Al. The effect of Ni and Al on the strength of the Ir-Nb binary alloy is discussed.     

苯甲醇在铂和钯电极上的电化学反应活性研究

为研究电极性能对苯甲醇（BA）反应活性的影响,用差示电化学质谱分析（DEMS）和循环优安法对0．1mol/L HCIO4中的2mmol/L苯甲醇在铂和钯电极上的电化学反应进行了研究。挥发性产物的在线质谱分析显示,苯甲醇和这些金属相互作用,部分离解成苯。CO2是检测出来的唯一一种氧化产物。相应的质谱信号显示出3种不同的组成。用伏安扫描时发现,每种组成的范围强烈依赖于电极性质,但以钯为电极时,每种组成的范围也随着伏安扫描时的电极电势范围的变化而变化。在电解还原过程中,铂和钯表现出不同的催化活性,在铂电极上发生分子的氢解和芳环的氢化作用,而在钯电极上芳环的氢化作用很少发生。