HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY DETERMINATION OF ANILINES WITH FLUORESCENT DETECTION AND PRE-COLUMN DERIVATIZATION

A simple, sensitive, and rapid reverse-phase high-performance liquid chromatography (RP-HPLC) method for the determination of anilines in water is proposed. The use of 2,7-diethylamino-2-oxo-2H-chromen-3-yl-benzothiazole-6-sulfonylchloride (coumarin 6-SO₂Cl) as a fluorigenic-labeling reagent was investigated. The label reacted with aniline within 30 min under mild conditions (ambient temperature, pH 9.0) to give sulfonamides that were separated by RP-HPLC employing fluorescence detection with an excitation wavelength of 470 nm and an emission wavelength of 520 nm. The optimum conditions for fluorescence, derivatization, and chromatographic separation were established. The calibration curves were linear for the range 0–800 ppb. The proposed method was applied for the determination of anilines in spiked drinking water samples and irrigation water samples with recoveries of 90.0–103.9% and relative standard deviations of 1.2–4.7%, respectively. This method showed good accuracy and repeatability that can be used for the quantification of aniline in real samples.     

248 nm excimer laser drilling PI film for nozzle plate application

In this study, drilling of polyimide (PI) film by using a 248 nm excimer laser through photomask projection is presented. The parameter effects of laser fluence, shot number and repetition rate on the processing results are realized. A high-quality of microhole array with 50 μm thick PI film has been fabricated. When the projection process is carried out, differences in the diameters of the microhole in the front and back sides of the PI are observed, which cause a conical shape in the kerf. The formation of this conical shape in terms of laser process parameters is discussed. Besides, to improve the laser machining quality of PI microholes, the effects of the process parameters are investigated and characterized. In addition, before excimer laser drilling PI is conducted, the PI surface is pre-coated with, or left without, a thin film material to observe the formation of debris. The results shows that the formation of debris can be reduced significantly when a pre-coated thin film is applied on the PI surface.     

A new integrated polishing process design for plastic mold steel to mirror-like surface

This paper aims to propose the design of a new polishing tool, a clamp with a flexible polishing head (or CFPH) for polishing plastic mold steel. The investigation/evaluation of this new tool’s performance in polishing is also included in this paper. The design of this brand new flexible clamp with a polishing head is, first of all, based on the application of the concept of weakening gap in the study of Fuh [1] increase in the freedom of micro-movement of the clamp is available. Second, various analyses and tests are done by the finite element method (FEM). Then, through the spectrogram, we analyze this tool’s machining characteristics. Furthermore, by the performance on large waves, medium waves, and small waves of the workpiece, we evaluate the working efficiency and set up a set of polishing strategies. This module of machining strategy process contains the combination of cutting and polishing one kind or multi-kind machining modes and the complementary precision processing methods. Finally, we propose a set of polishing integration process skills specifically on S-STAR*. We also verify our analysis with 3D profiles and the surface roughness measurement instrument. These verified analyses show that roughness and shape precision can be reached to Ra0.006, Rmax0.08, and PV0.084 μm respectively. This new invention, by the spectrum analysis, can significantly improve large wavelength accuracy up to 83.9 %, medium wavelength accuracy 82.5 %, and small wavelength accuracy 80.2 %. To conclude, we aim to set up a mirror-like surface polishing tool for plastic mold steel. This proposal is prudentially verified and should be considered theoretically and practically successful.     

Determination of methyl gallate in Bauhinia retusa extract by high-performance liquid and thin-layer chromatography

Two stability-indicating chromatographic methods are reported for the determination of methyl gallate in crude extracts of Bauhinia retusa. Separation by high performance thin layer chromatography was conducted on silica gel aluminum sheets using 9.5:0.5:0.2 (v/v/v) chloroform:methanol:acetic acid at 280 nm. The results from the 2–40 µg/band were used to prepare a linear calibration graph. The limits of detection and quantitation were 0.5 and 1.5 µg/band, respectively. The reverse phase high performance liquid chromatographic isolation of methyl gallate was performed at ambient temperature with an injection volume of 10 μL. The mobile phase consisted of 40:60 (v/v) methanol:0.1% ortho-phosphoric acid. The separation was performed at 1 mL/min using a detection wavelength of 280 nm. The calibration graph for methyl gallate was rectilinear from 0.02–40 µg/mL with limits of detection and quantitation of 0.004 and 0.010 µg/mL, respectively. For both methods, intra-day and inter-day precision were evaluated and the relative standard deviation was less than 2%, indicating good precision. The robustness was evaluated by making small and deliberate changes to appropriate parameters and the calculated relative standard deviation was less than 2%.The chromatographic methods were employed to determine methyl gallate in crude Bauhinia retusa extracts.     

A compact Schwarzschild soft X-ray microscope with a laser-produced plasma source

A compact Schwarzschild soft X-ray microscope using a laser-produced plasma soft X-ray source has been developed. The laser-produced plasma source, which is small but of high brilliance, has made it possible to use the soft X-ray microscope in a small laboratory. The microscope is composed of a Schwarzschild objective and a grazing incidence mirror condenser. Image contrast for biological specimens in soft X-ray regions is investigated briefly. It is possible to observe the fine structures of a thin specimen at a wavelength of 15 nm; at this wavelength high-contrast images of biological specimens have been obtained with a single laser shot of pulse width of 8 ns at a resolution of 0·3 μm. The resolution of the system is limited by the detector.     

用于宽带光谱滤波的光学衍射神经网络的设计

光谱处理在光学研究和应用中具有重要意义。针对特定任务,已经开发了各种设备和仪器进行光谱的滤波、整形与分析、波长解复用等,但还没有具有先进处理能力的多任务光谱处理设备。设计了一种用于光谱滤波的衍射神经网络,其由相位调制型衍射层与探测层构成。在训练过程中加入了波长参数,以实现对宽带信号的处理;通过损失函数的设计,可以对输出光谱进行控制。以可见光波段的宽带信号为例,实现了单、双通带光谱滤波,且中心波段的宽度和相对强度可调节。证明了该光学衍射神经网络可以有效处理宽带光谱,并为实现更复杂的光谱处理任务奠定了基础。     

High-power bipolar multilevel pulsed electroporator

A novel, compact, high-voltage, bipolar electroporator is reported that produces single or multiple, symmetrical or asymmetrical, high-power square wave pulses up to ±1 kV and 100 A. A wide 1 μs to 10 ms pulse duration is provided with high resolution of 1 V and 0.5 μs. The device provides increased flexibility due to enhanced control of the pulse shape and delivered energy.     

Books Received for Review

Smartphone image sensor response is compared for broadband and narrowband (340 nm and 380 nm) UVA wavelengths (320–400 nm) based on previous studies that have demonstrated quantitative response to solar radiation at 380 nm and 340 nm to reconstruct broadband irradiance. This article compares broadband and narrowband sensing using a common readily accessible smartphone equipped with a broadband UVA filter that displayed strong sensitivity to long wavelength UVA irradiances from 370 nm with a maximum at 380 nm. However, the use of narrow passband and neutral density filters allowed quantitative observations at the biologically significant wavelength of 340 nm. Narrow passband filter observations also had less variation at 340 nm than observed for broadband measurements. The results indicate that the smartphone image sensor, with the addition of narrow passband and neutral density filters, is a viable tool for UVA observations, but is unsuitable for broadband filter measurements.     

半导体温度传感器在直升飞机测温上的应用

半导体温度传感器具有较高的精度和良好的线性输出。采用LM135型半导体温度传感器,与CPU、数码管接口,经A/D和V/F转换等信号处理,成功研制了某直升飞机数字大气温度显示器,取代了双金属片指针式温度计。试验结果表明LM135传感器在-55℃～70℃可以实现单点校准,在-60℃～-55℃出现非线性,可以通过程序进行单点补偿校准。     

Effect of process parameters in nanosecond pulsed laser micromachining of PMMA-based microchannels at near-infrared and ultraviolet wavelengths

This paper presents investigations on the effects of nanosecond laser processing parameters on depth and width of microchannels fabricated from polymethylmethacrylate (PMMA) polymer. A neodymium-doped yttrium aluminium garnet pulsed laser with a fundamental wavelength of 1,064 nm and a third harmonic wavelength of 355 nm with pulse duration of 5 ns is utilized. Hence, experiments are conducted at near-infrared (NIR) and ultraviolet (UV) wavelengths. The laser processing parameters of pulse energy (402–415 mJ at NIR and 35–73 mJ at UV wavelengths), pulse frequency (8–11 Hz), focal spot size (140–190 μm at NIR and 75 μm at UV wavelengths) and scanning rate (400–800 pulse/mm at NIR and 101–263 pulse/mm at UV wavelengths) are varied to obtain a wide range of fluence and processing rate. Microchannel width and depth profile are measured, and main effects plots are obtained to identify the effects of process parameters on channel geometry (width and depth) and material removal rate. The relationship between process variables (width and depth of laser-ablated microchannels) and process parameters is investigated. It is observed that channel width (140–430 μm at NIR and 100–150 μm at UV wavelengths) and depth (30–120 μm at NIR and 35–75 μm at UV wavelengths) decreased linearly with increasing fluence and increased non-linearly with increasing scanning rate. It is also observed that laser processing at UV wavelength provided more consistent channel profiles at lower fluences due to higher laser absorption of PMMA at this wavelength. Mathematical modeling for predicting microchannel profile was developed and validated with experimental results obtained with pulsed laser micromachining at NIR and UV wavelengths.     

Development and kinematic calibration for measurement structure of a micro parallel mechanism platform

This paper presents a micro-positioning platform based on a unique parallel mechanism developed by the authors. The platform has a meso-scale rectangular shape whose size is 20 × 23 mm. The stroke is 5 mm for both the x-and y-axes and 100 degrees for the α-axis. The platform is actuated by three sets of dual stage linear actuators: a linear motor for rough positioning and a piezo actuator for fine positioning. The developed micro-positioning platform has a measurement system that consists of three linear sensors. The position and orientation values of the movable platform can be measured directly and used in a feedback control system. Selecting 18 kinematic error parameters of a measurement system (feedback control system), a two-stage kinematic calibration method is proposed. Constant error parameters are found in the first stage and variable error parameters are found in the second stage of kinematic calibration. After kinematic calibration the position error is reduced to within 0.5 μm and error reduction rate is over 90%.     

SURFACTANT MEDIATED EXTRACTION OF TRITERPENES AND THEIR DIRECT HPLC ANALYSIS FROM THE MICELLAR SYSTEM

The pentacyclic triterpenes oleanolic acid (OA) and ursolic acid (UA) in Salvia triloba are attractive ingredients for cosmetic and pharmaceutical formulations. These triterpenoids are constitution isomers and differ only in the position of one methyl group in their chemical structures. Therefore it is difficult to achieve a baseline separation by standard RP-HPLC systems. Another challenge is that the complex plant contains a large variety of similar compounds. To achieve precise results for the target molecules, these compounds should be removed prior to analysis. Due to the large application of these two triterpenes, a fast quantification method is favored. If the triterpenes are extracted with aqueous two-phase systems, the target substances are enriched in a surfactant-rich phase. For this application, it is desirable to develop a method that is capable of quantifying both triterpenes directly by RP-HPLC without additional purification steps.

The optimal chromatographic conditions for pure substances as well as for crude surfactant-containing extracts were accomplished on a Nucleodur C18 ISIS column by isocratic elution with methanol/water/acetic acid/triethanolamine (90:10:0.04:0.02 v/v) as the mobile phase and a column temperature of 10°C. The flow rate was 0.6 mL/min, and the detection wavelength was 210 nm. With these parameters, a baseline separation was achieved and the calibration curve showed a very good linearity (R² > 0.999 for OA and UA) within the test range. The method is simple, rapid, and reliable for the quantification of crude extracts from plant material.     

Local field enhancement effects for nanostructuring of surfaces

We report on a method that allows the nanostructuring of surfaces with intense laser pulses. For this purpose isolated polystyrene spheres with diameters in the order of the laser wavelength were deposited on a silicon or glass surface. Illumination with short and ultrashort laser pulses produced holes underneath these particles. Calculations of the field near the particles make clear that geometrical optics, that is, focusing by a spherical lens, as well as near-field effects, contribute to the size and shape of these holes. This technique can be utilized for the parallel structuring of large surface areas with a single laser shot.     

Microfluidic channel depth determination with Tywman–Green interferometer

A microfluidic channel is fabricated on a silica wafer using reactive ion etching (RIE). The depth of the microfluidic channel has been measured using a surface profilometer and a Twyman–Green interferometer (TGI) setup. The TGI setup which mainly consists of a 660-nm wavelength He-Ne laser source, glass cube beam splitter and two prisms produced interference fringes based on the optical path difference between two interfering beams when the microfluidic channel is inserted into one of the beams. The TGI setup that was developed has shown high repeatability when measuring microfluidic channel depth and also eliminates back injection into the laser source and alignment criticality. The TGI setup applied a single photodiode to detect the shifting of the bright and dark fringe produced from the interference of the TGI. The depth of microfluidic channel obtained from the TGI is 1.79?±?0.31 μm using fringe shifting and intensity measurements, while according to the surface profilometer the depth of microfluidic channel obtained is 1.67?±?0.07 μm. The resolution of the TGI is 0.25 μm and can still go well below that depending on the wavelength of the laser source. This research describes the capability of the TGI to perform depth measurements on a microfluidic channel of a silica substrate which can also be improvised for other microscale devices and applications.     

Accurate Calibration of Mercury Vapour Indicators for Occupational Exposure Measurements using a Dynamic Mercury Vapour Generator

Abstract

An accurate and rapid calibration procedure for mercury vapour indicators used for occupational exposure measurements is described, using a dynamic mercury vapour generator traceable to the standard bell-jar calibration apparatus. The method provides greater flexibility, accuracy, and trace ability than the usual methods for the calibration of mercury vapour indicators used for occupational exposure measurements. The calibration procedure allows a correction to be applied to the mass concentration value displayed by the mercury vapour indicator. Measurement results from the mercury vapour indicator at the occupational exposure limit of 25 µg ·m^?3, following calibration, have been estimated to have an expanded uncertainty of 8%.     

Mechanical and Tribological Properties of Shot-Peened SAE 1070 Steel

The effects of shot peening pressure on the mechanical and tribological properties of shot-peened SAE 1070 steel strips were systematically investigated. The surface hardness of the shot-peened steel strips significantly increased with increased shot peening pressure due to the promoted cold work-hardening effect. The tribological results showed that the increased surface roughness of the shot-peened steel strips associated with increased shot peening pressure resulted in their increased friction by enhancing mechanical interlocking between two rubbing surfaces. The wear of the shot-peened steel strips decreased with increased shot peening pressure via their increased surface hardness. However, the shot-peened steel strips at shot peening pressures less than 345 kPa did not exhibit better wear resistance than the as-received steel strip, indicating that a certain intensity of shot peening was required to improve the wear resistance of the shot-peened steel strips. It could be concluded that the mechanical and tribological properties of the shot-peened steel strips were significantly influenced by the shot peening pressure.     

Controlled Synthesis and Optical Properties of Pure Gold Nanoparticles

Abstract

Gold nanoparticles were synthesized by laser ablation of a gold metallic disc at wavelengths of 532 nm and 355 nm with 7 ns pulse duration in the pure water. The colloidal gold nanoparticles were characterized by ultraviolet-visible absorption spectroscopy, transmission electron microscopy, and fluorescence spectrometry. The presence of a surface plasmon resonance peak around ～ 524 nm indicates the formation of gold nanoparticles. The formation efficiencies of gold nanoparticles in colloids were found to increase when ablating the gold metallic disc with a laser having a longer wavelength. The size distributions of the gold nanoparticles thus produced were measured by transmission electron microscopy. A reduction in mean diameter of the particles was observed with a decrease in the laser wavelength under the irradiation at a high fluence of 25 mJ/pulse. The fluorescence spectroscopy demonstrated that these gold nanoparticles are fluorescent, showing a strong blue emission intensity at 458 nm.     

Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop crosscoupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedforward control and a load torque identification with feedforward control. A digital integrated simulation system for the dual servo synchronous drive system is established.Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the worktable works with an unbalanced load. However, the system with proposed scheme shows good synchronous performance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8 μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on crosscoupled integrated feedforward compensation control,which can improve the synchronization precision.     

Nanoparticle shape and configuration analysis by transmission electron tomography

Tomographic reconstruction by transmission electron microscopy is used to reveal three‐dimensional nanoparticle shapes and the stacking configurations of nanoparticle ensembles. Reconstructions are generated from bright‐field image tilt series, with a sample tilt range up to ± 70°, using single or dual tilt axes. We demonstrate the feasibility of this technique for the analysis of nanomaterials, using appropriate acquisition conditions. Tomography reveals both cubic and hexagonal close‐packing configurations in multi‐layered arrays of size‐selected In nanospheres. By tomography and phase‐contrast lattice imaging, we relate the three‐dimensional shape of PbSe octahedral nanoparticles to the underlying crystal structure. We also confirm simple‐cubic packing in multi‐layers of PbSe nanocubes and see evidence that the particle shapes have cubic symmetry. The shapes of TiO₂ nanorod bundles are shown by tomographic reconstruction to resemble flattened ellipsoids.     

Noncontact simultaneous dual wavelength photoplethysmography: a further step toward noncontact pulse oximetry

We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and 880 nm). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of 16 frames/wavelength s, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation (S(p)O(2)) remotely. Results from an experiment on ten subjects, exhibiting normal S(p)O(2) readings, that demonstrate the instrument's ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a J. Bland and D. Altman [Lancet 327, 307 (1986); Statistician 32, 307 (1983)] test, the noncontact device to be comparable to a contact device as a monitor of heart rate. We highlight some considerations that should be made when using camera-based "integrative" sampling methods and demonstrate through simulation, the suitability of the captured PPG signals for application of existing pulse oximetry calibration procedures.