1‐Pyrenemethanol,a Useful Fluorometric Reagent for the Detection and Determination of Carboxylic Acids in Atmospheric Samples

Abstract

A rapid fluorometric procedure for the selective and sensitive determination of carboxylic acids, based on pre‐column derivatization using 1‐pyrenemethanol, was optimized and applied to atmospheric sampling. The optimum conditions for derivatization were determined to be: reaction solvent–dichloromethane, temperature ?44°C, reaction time ?30 min, and reagent/total acid ratio ?15. Separation of the derivatives of acids up to twenty carbons by reversed‐phase (C₈) chromatography was achieved in 25 min using a water/acetonitrile gradient with a limit of detection for the derivatives of 20 pg for a 20 µL injection. A scanning detector with good spectral resolution allows qualitative identification of the components in complex samples. When used in atmospheric analysis, the recoveries of carboxylic acids from spiked samples were >80% with repeatabilities below 10% RSD. Low molecular weight acids were encountered predominantly in the vapor phase (0.20 to 92 ng/m³), whereas higher molecular weight acids were found mostly in particulate form (0.15–129 ng/m³).     

An Inexpensive Sequential Injection Analyzer for the Analytical Laboratory

Abstract

A home‐made multiposition valve and a syringe pump were specially designed and fabricated using inexpensive and easily available materials and equipment in the laboratory. The hardware and software for controlling the devices and displaying the signal were developed. Both devices were combined to obtain a sequential injection analysis (SIA) system and used by incorporating with a spectrophotometric detector. The developed SIA analyzer is computerized. The SIA system can select the samples and reagent, which is then sequentially injected into the holding coil where the sample and the reagent zones are taking place. Both sample and reagent zones are delivered into a flow‐through detector where the reaction product is measured spectrophotometrically. The program for interfacing the SIA instrumentation with a personal computer was also developed using Microsoft Visual Basic?. This can enable a wide range of chromophores to be automatically detected. The fabricated SIA analyzer was tested for determining Fe(III) in standard solution based on Fe(III)‐thiocyanate complex. The RSD for 11 replicates determination of 4.0 mg/L iron was 1.08%. The detection limit (3σ) and the determination limit (10σ) were 0.34 and 1.13 mg/L, respectively. A linear calibration curve over the range of 1.0–7.0 mg/L iron and correlation coefficient of 0.9977 were established. The analyzer has been successfully applied to the determination of total iron in waters. Results obtained by both the proposed SIA and AAS methods were in excellent agreement.     

Biotinylated vanadium and chromium sulfide nanoparticles as probes for colocalization of membrane proteins

We report the microemulsion synthesis of vanadium and chromium sulfide nanoparticles (NPs) and their biological application as nanoprobes for colocalization of membrane proteins. Spherical V₂S₃ and Cr₂S₃ NPs were prepared in reverse microemulsion droplets, as nanoreactors, obtained by the surfactant sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) in nonpolar organic phase (heptane). Electron microscopic data indicated that the size distribution of the nanoparticles was uniform with an average diameter between 3 ÷ 5 nm. The prepared hydrophobic nanocrystals were transferred in aqueous phase by surface cap exchange of AOT with biotin‐dihydrolipoic ligands. This substitution allows the nanoparticles solubility in aqueous solutions and confer their bioactivity. In addition, we report the conjugation procedure between α‐Lipoic acid (LA) and biotin (abbreviated as biotin‐LA). The biotin‐LA structure was characterized by 1D and 2D NMR spectroscopy. The biotinylated vanadium and chromium sulfide nanoparticles were tested as probes for colocalization of glutamate receptors on sodium‐dodecyl‐sulfate‐digested replica prepared from rat hippocampus. The method suggests their high labeling efficiency for study of membrane biological macromolecules. Microsc. Res. Tech. 79:799–805, 2016. © 2016 Wiley Periodicals, Inc.     

采样样本的容量对雾滴尺寸测量精度影响的试验研究

用雾滴采集装置在自行建立的高压喷雾系统上对雾滴进行了样本采集,用机器视觉方法对雾滴尺寸进行了统计与测量,将机器视觉方法测量结果与PDPA测量结果相比较,深入分析了雾滴采样样本对雾滴尺寸测量精度的影响.试验结果表明:雾滴采样样本容量越大,雾滴尺寸测量精度也越高,当雾滴样本容量大于4 000个时,雾滴特征直径D0.632的测量精度可达5%以内;不同粒径的雾滴个体对雾滴尺寸测量精度的影响不同,大粒径雾滴对尺寸测量精度的影响远大于小粒径雾滴,雾滴尺寸测量时尤其应注意准确统计大粒径雾滴.     

3D and 2D structural characterization of 1D Al/Al2O3 biphasic nanostructures

1D Al/Al₂O₃ nanostructures have been synthesized by chemical vapour deposition (CVD) of the molecular precursor [^tBuOAlH₂]₂. The deposited nanostructures grow chaotically on the substrate forming a layer with a high porosity (80%). Depending on the deposition time, diverse nanostructured surfaces with different distribution densities were achieved. A three‐dimensional (3D) reconstruction has been evaluated for every nanostructure density using the Focus Ion Beam (FIB) tomography technique and reconstruction software tools. Several structural parameters such as porosity, Euler number, geometrical tortuosity and aspect ratio have been quantified through the analysis with specified software of the reconstructions. Additionally roughness of the prepared surfaces has been characterized at micro‐ and nanoscale using profilometry and AFM techniques, respectively. While high aspects ratio around 20–30 indicates a strong anisotropy in the structure, high porosity values (around 80%) is observed as a consequence of highly tangled geometry of such 1D nanostructures.     

Radon track imaging in CR-39 plastic detectors using confocal scanning laser microscopy

Confocal scanning laser microscopy (CSLM) has been used to provide the first images of radon track populations in two external CR-39 plastic detectors. Measurements of variables including track area distribution and estimates of the angle of track inclination (dip) derived from surface CSLM sections are presented. CSLM depth slices, combined with three-dimensional (3D) visualization techniques, provide a new, non-destructive way of examining the 2D and 3D geometry of the etched tracks within solid-state nuclear track detectors that may prove useful in complementing existing optical microscopy methods.     

离子色谱法和比色法测定饮用水中三氯乙酸的比较研究

对离子色谱法和比色法测定饮用水中三氯乙酸的效果进行了比较研究。结果表明,离子色谱法测定三氯乙酸的检测限为4.8μg/L,线性范围为0.1～10mg/L,加标回收率在98.7%～101%之间,相对标准偏差小于2%;比色法测定三氯乙酸检测限为80μg/L,线性范围为0.25～5mg/L,加标回收率在97.3%～104%之间,相对标准偏差小于3%。配对t检验结果表明,离子色谱法和比色法的结果没有显著性差异,两种方法均可作为饮用水中三氯乙酸的测定方法。     

Relative fatigue life estimation of cylindrical hollow rollers in general pure rolling contact

Solid and hollow cylindrical rollers in pure rolling contact have been modelled. The two rollers are subjected to a combined normal and tangential loading. The tangential loading is one‐third of the normal loading value. The finite element package, ABAQUS, is used to study the stress distribution and the resulting deformations in the bodies of the rollers. Then the Ioannides–Harris fatigue life model for rolling bearings is applied on the ABAQUS numerical results to investigate the fatigue life of the solid and hollow rollers. Using the fatigue life of the solid rollers as the reference fatigue life, the relative fatigue lives of hollow rollers are determined. Four main different hollowness percentages are been studied: 20, 40, 60 and 80%. The hollowness percentage is the ratio of the diameter of the hole to the outer diameter of the cylinder. For each of those hollowness percentages, two cases are studied – when the two rollers in contact are hollow and when one hollow roller is in contact with a solid roller. This study includes two main models: Model 1, where the two cylindrical rollers in contact are of the same size, and Model 2, where the two rollers in contact are not of the same size. The estimated relative fatigue lives of hollow rollers showed a great improvement of the fatigue life compared with solid rollers under the same loading conditions. This was a result of the redistribution of stresses in the contact zone in the case of hollow rollers. Redistribution of stresses over a larger volume of the roller body decreased the peak stress and reduced the volume under risk. Increasing the hollowness percentage from 20 to 60% increased the flexibility of the roller, and better stress distribution was achieved, which resulted in improving the fatigue life. Although 80% of hollowness rollers have more flexibility than 60% of hollowness rollers, the bending stresses (σ_b) on the inner surface of the rollers tend to decrease the fatigue life. Copyright © 2007 John Wiley & Sons, Ltd.     

MRT letter: Extended depth from focus reconstruction method for stretch zone measurement in 15-5PH steel

The stretch zone width (SZW) data for 15‐5PH steel CTOD specimens fractured at ?150°C to + 23°C temperature were measured based on focused images and 3D maps obtained by extended depth‐of‐field reconstruction from light microscopy (LM) image stacks. This LM‐based method, with a larger lateral resolution, seems to be as effective for quantitative analysis of SZW as scanning electron microscopy (SEM) or confocal scanning laser microscopy (CSLM), permitting to clearly identify stretch zone boundaries. Despite the worst sharpness of focused images, a robust linear correlation was established to fracture toughness (K_C) and SZW data for the 15‐5PH steel tested specimens, measured at their center region. The method is an alternative to evaluate the boundaries of stretched zones, at a lower cost of implementation and training, since topographic data from elevation maps can be associated with reconstructed image, which summarizes the original contrast and brightness information. Finally, the extended depth‐of‐field method is presented here as a valuable tool for failure analysis, as a cheaper alternative to investigate rough surfaces or fracture, compared to scanning electron or confocal light microscopes. Microsc. Res. Tech. 75:1155–1158, 2012. © 2012 Wiley Periodicals, Inc.     

Identification and quantification of microstructures formed during nanocrystallization of amorphous (Fe, Co)-Nb-(Si, B) systems

The effect of addition of Si and variation of the Fe/Co ratio on the evolution of the nanostructure was studied in a modification of the Fe–Nb–B system. The entire system (Fe, Co)₇₃Nb₇(Si, B)₂₀ was prepared in an amorphous state by rapid quenching using the planar flow casting method over a wide range of Fe/Co atomic ratios, ranging from 0 to 1. Nanocrystallization was investigated by evolution of the electrical resistivity with time and temperature. The microstructural analysis was performed using transmission electron microscopy as well as electron and X‐ray diffraction. The results from microscopy observations were used to determine the distribution of grain size, which in these alloys attain very small dimensions of ～5–8 nm. New algorithms of microscope image analysis were used for grain size determination, crucial for quantifying the microprocesses controlling nucleation and growth from the amorphous rapidly quenched phase.     

Hydrogenated styrene–isoprene–butadiene rubber: optimisation of hydrogenation conditions and performance evaluation as viscosity index improver

Hydrogenated styrene–isoprene–butadiene rubber (HSIBR) was prepared through the hydrogenation reaction of self‐prepared styrene–isoprene–butadiene rubber using a Ziegler–Natta type catalyst prepared with nickel naphthenate (Ni) and aluminum triisobutyl (Al). The precursors and corresponding hydrogenated polymers were characterised using size exclusion chromatography, proton nuclear magnetic resonance (¹H NMR) spectroscopy, differential scanning calorimetry and thermal gravimetric analysis. The effects of various reaction parameters on the level of hydrogenation, calculated from ¹H NMR spectroscopy, were investigated in the current paper. A maximum of 98% hydrogenation was obtained under the following conditions: Al/Ni molar ratio, 6; catalyst amount, 3 mg Ni per g of polymer; time, 3 h; temperature, 60°C; H₂ pressure, 4 MPa and polymer concentration, 10 wt.%. Moreover, a different SAE 5W‐30 multigrade oil (5 CST hydroisomerisation dewax base oil) was formulated using HSIBR samples as viscosity index improvers (VII). The effect of butadiene/isoprene mass ratio in HSIBR on the performance of VII for lubricants was investigated here for the first time. HSIBR used as VII for lubricants integrated some advantages of hydrogenated styrene–butadiene rubber and hydrogenated styrene–isoprene rubber. Copyright © 2014 John Wiley & Sons, Ltd.     

Dynamic confocal scanning laser microscopy methods for studying milk protein gelation and cheese melting

Dynamic confocal scanning laser microscopy (CSLM) methods were developed to enable observation of milk protein gelation and cheese melting. Protein aggregation and the formation of gel networks in renneted full-fat and low-fat milks and glucono-δ-lactone (GDL)-acidified skim milks were observed by CSLM and observations correlated with increases in shear modulus (G′) and dynamic viscosity (η*) as determined by dynamic amplitude oscillatory rheology. Confocal scanning laser microscopy observation of low-fat and full-fat cheeses showed changes in fat distribution and an increase in staining intensity during cheese melting.     

Modeling and simulation of droplet translocation and fission by electrowetting-on-dielectrics (EWOD)

This paper discusses methods of microfluidic droplet actuation by means of electrowetting-on-dielectrics (EWOD) and provides a technique for modeling and simulating a microfluidic device by using the computational fluid dynamics (CFD) program, Flow3D. Digital or droplet microfluidics implies the manipulation of droplets on a scale of nanoliters (10⁻⁹ L) to femtoliters (10⁻¹⁵ L), as opposed to continuous microfluidics that involve the control of continuous fluid within a channel. The two operations in focus here are droplet translocation (moving) and droplet fission (splitting), in which the pressures and velocities within the droplet are analyzed and compared to existing works, both theoretical and experimental. The variation in the pressure of the leading and trailing faces of a droplet indicates the variation in surface energy—an important parameter that explains how a droplet will move toward a region of higher electric potential. The higher voltage on one side of a droplet reduces surface energy, which leads to an induced pressure drop, thus resulting in fluid motion. Flow3D simulations are for both water and blood droplets at voltages between 50 Vand 200 V, and the droplet size, surface properties (Teflon coated), and geometry of the system are kept constant for each operation. Some peculiarities of the simulation are brought to light, such as instabilities of the system to higher voltages and fluids with higher dielectric constants, as well as the creation of a tertiary droplet when the applied voltage causes a large enough force during fission. The force distribution across the droplet provides a general understanding of the electrowetting effect and more specifically allows for a comparison between the effects that different voltages have on the forces at the droplet surface. The droplet position and mean kinetic energy of the droplet are also investigated and compared to other works, proving the dynamics of a droplet motion found here.     

离子色谱用于标准物质硝酸根定值的方法研究

用离子色谱研究标准物质硝酸根定值的方法。采用阴离子分析柱IonPacAS19(2mmI.D.×250mm),抑制型电导检测,进样体积25μL,NaOH为等度淋洗液,通过正交设计L9(34)表安排试验,确定优化的色谱条件。NO3-的检出限是0.007mg/L,方法精密度RSD为0.36%,方法线性范围是1.0~100mg/L,样品平均加标回收率在94.2%~104%之间。利用校正曲线的稳定性检查,质控样可靠性检查和回收率检验证明该分析方法是可靠的。该方法简单、快速、灵敏、重复性好,已用于标准物质硝酸根的定值。     

Applicability of the energy dispersive x‐ray microanalysis for quantification of irregular calcium deposits on fruit and leaf cuticles

In our studies, we evaluated the relation between CaCl₂ concentration and the scanning electron microscope–energy dispersive x‐ray microanalysis parameters, net intensity, peak/background and standardized percentage of atoms and percentage of weight after application of single microdroplets on enzymatically isolated tomato fruit cuticles and apple seedling leaves. After analysis, the Ca/Cl ratio was calculated and the area ultimately covered with Ca and Cl within the droplet spread area determined. According to our findings, all evaluated parameters were influenced by both droplet volume and calcium chloride concentration, whereas Pearson's analysis revealed a strong correlation between net intensity and area ultimately covered by Ca or Cl, respectively. Simple linear regressions for net intensity, peak/background and Ca/Cl ratio showed variable determination coefficients (R²) ranging between 0.49 and 0.79. Multiple regression equations comprising net intensity, Ca/Cl ratio and deposit area were established to estimate the amount of calcium present on the cuticles. Equation slopes depended on droplet volumes, with determination coefficients of 0.89 and 0.81 for 0.5 and 1.0‐μL droplets, respectively. The importance of the physicochemical properties of the spray solution was exploited in another study where a hydrophobic or a hydrophilic adjuvant was added to a 10 g L^?1 CaCl₂ solution, which was applied to apple seedling leaves. The addition of adjuvants increased values of net intensity and peak/background, which correlated significantly with the area covered by calcium. The importance of the methodology for studies on the interaction between leaf applied fertilizers (also extended to agrochemicals) and the characteristics of target surfaces is discussed.     

Characteristics of auto-ignition and micro-explosion behavior of a single droplet of water-in-fuel

The characteristics of auto-ignition and micro-explosion behaviors of a single fuel droplet have been investigated experimentally with varying droplet sizes, ambient temperature, and water content. The fuel used for this experiment was pure n-decane, which was emulsified with several water content varied from 10% to 30% to compare the effects of water content in the emulsified fuel. Imaging with a high-speed digital camera was adopted to measure the ignition delay and flame life-time, as well as to observe micro-explosion behavior. The increase of droplet size and furnace temperature causes a decrease of the ignition delay time. The flame life-time is augmented as the droplet size increases, however it doesn’t seem to be affected by the ambient temperature relatively. As the water content increases, the ignition delay increases and the micro-explosion behavior is strengthened. The start timings of micro-explosion and fuel puffing are compared for different droplet sizes and the amount of water content.     

A method for structure analysis of nanomaterials by electron diffraction: Phase identification and unit cell determination

We report a quick and easy method for a random selected area electron diffraction (SAED) pattern without rotating and tilting the specimen to perform phase identification and unit cell determination by combined with the XRD softwares. If your TEM is well aligned and camera length is carefully corrected, two‐dimensional (2D)‐SAED pattern can be directly transformed to 1D‐profile after the center determination of pattern, this profile is then imported to XRD analysis packages. Finally, phase identification and unit cell determination can be performed after peak search or precise peak position determined by profile fitting. Two examples, flaky‐like TiO₂ nanomaterial and TiO₂ nanotubes precipitated by the silver nanoparticles, were tested and verified for the validation of phase identification and unit cell determination using this method; the successful crystallographic analysis of one single gold nanocrystal indicates it is still validate for the nanocrystals with the smaller diffraction volume, but need two or more random tilt SAED patterns. This method could be further used in the quantitative phase analysis, structure determination and Rietveld refinement for the nanomaterials if the reliable integrated intensity can be extracted. Microsc. Res. Tech. 76:641–647, 2013. © 2013 Wiley Periodicals, Inc.     

微波消解-离子色谱法检测茶叶中痕量氟离子

通过微波消解法、碱熔法和去离子水提取3种前处理方法相比较,确定微波消解的前处理条件;并对色谱柱条件进行优化,建立微波消解-离子色谱检测茶叶中的痕量氟的方法。本方法最低检出限为0.30mg/kg,线性系数为0.9996,测定值相对标准偏差为3.72%,回收率范围为80%～110%。该法与碱熔法和去离子水提取法相比具有空白值低、操作简便、准确性好、灵敏度高、检测限低等优点。     

化学雾化冷原子吸收法测定人尿中的汞含量

目的:建立一种化学雾化冷原子吸收光谱法测定人尿中汞含量的方法。方法:样品经加酸定容处理后,通过对介质酸度、硼氢化钠浓度、载气流速的优化,直接测定人尿中汞的含量。结果:在选定的条件下,该方法的检出限(3σ)为0.038μg/L,回归方程:y=0.06749x+0.00562,线性范围:0~5.0μg/L,回收率95.2~104.8%,相对标准偏差(RSD,n=7)为1.46~3.23%。结论:本方法准确、可靠、无记忆效应,适合大批量人尿中汞的简便快速测定。     

Effect of sintering temperature and time intervals on workability behaviour of Al–SiC matrix P/M composite

The investigation on the effect of sintering temperature and time intervals on workability behaviour of Al–SiC powder metallurgy composites during cold upsetting was attempted in the present work. Three levels of sintering temperature and time have been considered to evaluate their effect on workability behaviour. The amount of SiC reinforcement content has been varied as 0%, 10% and 20%. The experimental results were analyzed for workability under triaxial stress state condition as a function of the relative density. The Formability Stress Index (β_σ), the Formability Strain Index (β_ε), stress ratio parameters namely σ_θ/σ_eff and σ_z/σ_m were obtained for all the cases. As a result, the exhibited tremendous variations in the various parameters for different sintering temperatures and time intervals were studied and reported.