Regional characteristics of naturally occurring radionuclides in surface sediments of Chinese deserts and the Keum River area of Korea

Naturally occurring radionuclides (NORN) such as ⁴⁰K, ²²⁶Ra and ²³²Th from 44 surface sediment samples collected from four desert regions of Chinese were determined to investigate the regional characteristics of the source areas of Asian dust. The radionuclides for 41 surface sediment samples collected from seven sites of the Keum River area in Korea were also determined to compare the regional characteristics with the Chinese desert area. The specific activities (SA) and the specific activity ratios (SAR) of the radionuclides were investigated for distinguishing the source region of Asian dust. The SA of ²²⁶Ra and ²³²Th as well as the SAR of ²²⁶Ra/⁴⁰K and ²³²Th/⁴⁰K were found to be useful to characterize source area and tracing Asian dust.     

Influence of mesoporous structure type on the controlled delivery of drugs: release of ibuprofen from MCM-48, SBA-15 and functionalized SBA-15

Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively) have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous materials functionalized with octadecyl chains.     

Ag nanoparticles deposited onto silica,titania, and zirconia mesoporous films synthesized by sol–gel template method

A variety of Ag nanoparticles/oxide mesoporous films with templated silica, titania, and zirconia was synthesized by sol–gel method at glass, aluminum, and silicon substrates using metal alkoxides (tetraethoxysilane, titanium tetraisopropoxide, and zirconium tetrapropoxide) and AgNO₃ as precursors of oxide films and Ag nanoparticles, respectively, and Pluronic P123 as a template agent. Oxide films alone and Ag/oxide composites were characterized using hexane adsorption, X-ray diffraction (XRD), Raman and ultraviolet (UV)/vis spectroscopies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The distribution of Ag nanoparticles within the films, their sizes, intensity, and position of surface plasmon resonance (SPR) absorbance band at λ = 400 nm, as well as the textural and structural characteristics of whole films depend on treatment temperature, types of substrates and oxide matrices, oxide crystallization, and Ag content. Ag nanoparticles form preferably on the outer surface of the films under lower sintering temperatures if the amount of loaded silver is low. Oxide crystallization (e.g., TiO₂) promotes silver embedding into the outer film layer. At higher silver content (≥10 at.%) and higher calcination temperature (873 K), silver nanoparticles could be entrapped more uniformly along the film profile because of more intensive evaporation of silver droplets from the outer surface of the films on heating.     

On the structure and cure acceleration of phenol-urea-formaldehyde resins with different catalysts

Phenol-urea-formaldehyde (PUF) resins with different catalysts [calcium oxide (CaO), sodium carbonate (Na₂CO₃), zinc oxide (ZnO), and magnesium oxide (MgO)] were prepared to accelerate the cure of the resin at low temperature. The cure-acceleration effects of catalysts on chemical structure and cure characteristics of PUF resins were investigated by using both liquid ¹³C nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The liquid ¹³C NMR analysis indicated that the catalyst such as CaO seemed to present a retarded effect on the polycondensation reaction of phenolic components with urea units, while the Na₂CO₃ appeared to promote the self-condensation reaction of phenolic methylol groups at para position toward the formation of para-para methylene linkage. Both ZnO and MgO in PUF resins promoted self-condensation reaction of para methylol groups and condensation reaction of ortho methylol groups with para methylol groups. The catalysts such as Na₂CO₃, ZnO, and MgO can make PUF resins cure at a low temperature. Among these catalysts, the MgO had the most significant accelerating effect on polycondensation and cure reaction of PUF resin.     

A New Chromium(III) Microelectrode Based on Self‐Assembled Diethylenetriamminepentaacetic Acid‐Poly(fuchsin basic) Modified Electrode

A new selective, sensitive, and rapid response microelectrode for microamount chromium(III) determination was developed. For the electrode preparation, fuchsin basic was electropolymerized onto a carbon microdisk electrode, and then diethylenetriamminepentaacetic acid (DTPA) was self‐assembled on the electrode surface by the reaction between DTPA and poly(fuchsin basic). The determination conditions were optimized. The electrode showed a linear response to Cr³⁺ ions in the concentration range of 1.0×10^?6?1.0×10^?4 M and exhibits a super‐Nernstian slope of 32.5±0.4 mV per decade. The detection limit is 3.6×10^?7 M. The response time of the electrode is less than 10 s, and it can be used for at least 2 months with limited considerable divergences in its potentials. The proposed electrode was applied for monitoring the chromium ion level in wastewater of chromate industries.     

Microextraction,capillary electrophoresis,and mass spectrometry for forensic analysis of azo and methine basic dyes from acrylic fibers

Designed experiments based on a simplex mixture design were employed to explore the effects of three solvent components (water, formic acid, and aqueous acetic acid), extraction time, and extraction temperature for the automated microextraction of basic (cationic) dyes from acrylic fibers. Extractions were conducted by an automated liquid handling system, and dye extraction was evaluated using a UV/visible microplate reader. Highest extraction efficiency for two subclasses of basic dyes (methine and azo) from acrylic fibers was achieved with an extraction solvent containing 88% formic acid/12% water. Cationic dyes were analyzed by capillary electrophoresis using a 45 mM ammonium acetate buffer in acetonitrile–water at pH 4.7. The utility of microextraction combined with capillary electrophoresis–mass spectrometry for analysis of extracts from trace fibers was demonstrated by the detection and characterization of three basic dyes extracted from a 2-mm length of single acrylic fiber.     

A fluorescent chemical sensor for Hg(II) based on a corrole derivative in a PVC matrix

A fluorescent chemical sensor for Hg(II) using 5,10,15-tris(pentafluorophenyl)corrole (H₃(tpfc)) as fluorophore is described in this paper. The response of the sensor is based on the fluorescence quenching of H₃(tpfc) by coordination with Hg(II). H₃(tpfc) based sensor shows a linear response towards Hg(II) in the concentration range from 1.2 × 10⁻⁷ to 1.0 × 10⁻⁴ M, with a working pH range from 5.0 to 8.0. The response time for Hg(II) concentration ≤1.0 × 10⁻⁵ M is less than 5 min. The sensor shows good selectivity for Hg(II) over alkali, and alkaline earth, and most of transition metal cations. The effect of the composition of the sensor membrane has been studied and the experimental conditions optimized. The corrole based sensor membrane can be easily regenerated just by washing with blank buffer solution after each measurement. The sensor has been used for determination of Hg(II) in water samples with satisfactory results.     

杂交元零能模式抑制的正交基本变形模式方法

通过杂交元位移场直接推导了单元基本变形模式,并且采用联合正交条件提出一种新的正交化方法,所得到的正交基本变形模式不仅具有简单的变形特征而且和材料参数无关,可以方便有效地考察单元性能,为评价不同杂交元提供了一个统一的参考标准．在此基础上利用柔度矩阵正定性给出一种简单有效的零能模式识别方法,并进一步利用基本变形模式和初始应力模式之间耦合关系,提出一种抑制杂交元零能模式的假设应力场方法,同时指出基本变形模式正交性是抑制单元零能模式的充分必要条件．2D-4节点和3D-8节点单元的数值算例说明了该文基本变形模式方法的有效性．     

基于HSI高光谱和TM图像的土地盐渍化信息提取方法

选择黄河三角洲垦利县代表性盐碱化区域为研究区,以2011年3月15日HJ-1A卫星HSI高光谱影像和2011年3月22日TM影像为信息源,经几何纠正、图像裁剪、大气校正等预处理,分析不同盐渍化程度土地、水体、滩涂等主要地类的光谱特征,确定地类信息提取特征波段。结合土壤盐分含量,采用定量与定性相结合规则,构建地类信息提取模型,以决策树分类方法进行图像分类,提取土地盐渍化信息。利用地表点位土壤含盐量数据对地表土地盐渍化程度的化学分析结果,对遥感解译数据进行精度验证,并对高光谱和多光谱影像的分类精度进行比较分析。结果表明：HSI图像的总体分类精度达96.43%,Kappa系数为95.59%,而TM图像的总体分类精度为89.17%,Kappa系数为86.74%,说明相比多光谱TM数据,基于高光谱图像可以更为准确有效地提取土地盐渍化信息;由分类结果图可以看出,高光谱影像土地盐渍化的区分度高于多光谱影像。该研究探索了高光谱图像土地盐渍化信息的提取技术方法,提供了不同盐渍化土地的分布比例数据,可为黄河三角洲滨海盐碱土地资源的科学利用与管理提供决策依据。     

棱镜-光栅-棱镜分光模块整体化设计及衍射特性分析

PGP模块是超光谱成像仪中重要分光器件。为了能够在制作前有效预测PGP整个系统的衍射效率分布及其衍射特性,提出了PGP整体化设计方法。从体位相全息光栅设计角度出发,结合棱镜与光栅各项参数的制约关系,编制了计算PGP整体衍射效率的分析软件,综合考察了棱镜与光栅各项参数对PGP模块衍射特性的影响,讨论了光栅布拉格波长的漂移特性,据此设计了一种用于成像光谱仪的宽波段高衍射效率PGP分光模块。模拟结果表明：棱镜1材料的色散系数越小,PGP的光谱带宽越窄;光栅布拉格波长的漂移增大了PGP模块和光栅的光谱带宽,带宽增大使光栅的角度选择性随之增大,拓宽了棱镜1材料的选择要求;棱镜1顶角、光栅的胶层厚度和相对介电常数调制度等参数是影响PGP衍射效率分布的重要因素,制作时需要精确控制。利用此方法设计的PGP分光模块在400～1 000 nm波段范围内衍射效率不低于50%,并给出具体设计参数,这对PGP制作具有一定的参考价值。