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61.
Nano crystalline pure and Mg doped ceriaparticles were synthesized by simple chemical co-precipitation method using cerium nitrate hexahydrate as a source material and magnesium nitrate as doping precursor at room temperature. The effect of doping were investigated by X-ray diffraction pattern(XRD), FT-Raman,fourier transform infrared spectroscopy(FTIR), Ultraviolet spectroscopy(UV), photoluminescence spectroscopy(PL), field emission scanning electron microscope(FESEM) and high resolution transmission electron microscopy with energy dispersive spectroscopy (HRTEM &EDS). The X-ray diffraction pattern and FT-Raman studies showed that the prepared samples were nano particulates with cubic fluorite structure. The XRD pattern analysis showed that the size of the particles ranged from 13 to 20?nm, however 4?wt% Mg doping results in reduction of particle size compared with other doping concentrations. The effects of Mg concentration on various structural parameters of the prepared samples were also determined. The slight blue shift observed upon doping in UV–Vis absorption region around 330–360nmrecorded for reduction in particle size. The FTIR unveils the presence of Metal oxygen bonds below 700?cm?1in the prepared samples. All samples showed a broad emission band at 430?nm with linearly increasing intensity with respect to dopant concentrations. The Spherical morphology with weak agglomeration was identified through FESEM and HRTEM analysis. The elemental analysis of Ce, O and Mg were confirmed through EDS analysis. 相似文献
62.
A heavy crude oil has been treated with deuterated alkylating reagents (CD3I and C2D5I) and directly analyzed without any prior fractionation and chromatographic separation by high-field Orbitrap Fourier Transform Mass Spectrometry (FTMS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) using electrospray ionization (ESI). The reaction of a polycyclic aromatic sulfur heterocycles (PASHs) dibenzothiophene (DBT), in the presence of silver tetrafluoroborate (AgBF4) with ethyl iodide (C2H5I) in anhydrous dichloroethane (DCE) was optimized as a sample reaction to study heavy crude oil mixtures, and the reaction yield was monitored and determined by proton nuclear magnetic resonance spectroscopy (1H-NMR). The obtained conditions were then applied to a mixture of standard aromatic CH-, N-, O- and S-containing compounds and then a heavy crude oil, and only sulfur-containing compounds were selectively alkylated. The deuterium labeled alkylating reagents, iodomethane-d3 (CD3I) and iodoethane-d5 (C2D5I), were employed to the alkylation of heavy crude oil to selectively differentiate the tagged sulfur species from the original crude oil. 相似文献
63.
《Food Control》2015
Mycotoxins are secondary metabolites produced by filamentous fungi that usually contaminate food products. Coffee is a natural product susceptible to mycotoxin contamination. The present study evaluates the presence of nivalenol, deoxynivalenol, T-2 and HT-2 Toxin, diacetoxyscirpenol, aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, fumonisin B1, fumonisin B2, ochratoxin A, zearalenone, enniatin A, enniatin A1, enniatin B, enniatin B1, and beauvericin in coffee samples, using liquid chromatography tandem mass spectrometry (LC-MS/MS). The results show that zearalenone was not present in any sample. In the positive samples the contents of fumonisins ranged from 58.62 to 537.45 μg/kg, emerging mycotoxins ranged from 0.10 to 3569.92 μg/kg, aflatoxins ranged from 0.25 to 13.12 μg/kg, and trichothecenes, excepting nivalenol, ranged from 5.70 to 325.68 μg/kg. Nivalenol presented the highest concentrations, from 0.40 to 25.86 mg/kg. Ochratoxin A ranged from 1.56 to 32.40 μg/kg, and five samples exceeded the maximum limit established by the European Commission. 相似文献
64.
本研究分析了钢铁企业焦化和烧结两个重点工序中烟气污染物排放现状和钢铁行业当前的环保政策。对焦化及烧结烟气污染物的排放特征进行了分析,并通过对比燃煤电厂烟气特点,提出可以综合电厂烟气治理模式和自身特点改进的技术路线。结合某大型国有钢铁企业的脱硫脱硝装备对其环保现状进行了分析。针对焦化和烧结工序的典型污染物硫、硝、尘现有的源头减排、过程控制及末端处理技术,分析其优缺点。进而提出了3条可实现烟气污染物超低排放的技术路线,即半干法脱硫耦合选择性催化还原脱硝、半干法/湿法耦合臭氧氧化脱硝、活性焦脱硫脱硝一体化技术,重点介绍了这些技术在某大型钢铁企业的应用实践及应用效果。并基于全过程耦合技术,分别在焦化和烧结工序中提出了多污染物协同去除技术及应用,即焦炉低氮燃烧技术耦合末端活性焦多污染物协同控制技术、烧结烟气循环技术耦合末端活性焦多污染物协同控制技术。最后结合几种技术路线的应用实践,对未来钢铁产业的烧结及焦化工序超低排放技术的选择提出合理化建议。 相似文献
65.
讨论了3种制样方法对直流辉光放电质谱法(dc-GDMS)检测氮化硼中的Na、Mg、Al、Si等27种杂质元素的影响。3种制样方法分别如下所示:方法1,直接把氮化硼压在铟薄片上;方法2,把氮化硼压在铟薄片上后,再盖上一层铟罩;方法3,把压碎后的氮化硼放在针状钽勺上。在优化的辉光放电参数下对比了3种不同制样方法对基体信号强度的影响。试验表明:在方法1中,当氮化硼尺寸约为3mm×3mm,厚度小于1mm时,基体11B的信号可达1.8×107 cps;在方法2中,选择铟孔大小合适的铟罩,基体11B的信号可达1.0×107 cps;方法3获得基体信号强度比方法1、方法2高一个数量级。大部分元素在中分辨率下可获得较好的结果,而对于在高分辨率下也较难分离的元素,可选择丰度较低的同位素在中分辨率下进行测定,如Ge选择70Ge+,Se选择82Se+,Cd选择111Cd+,Sn选择119Sn+,Ag选择109Ag+,Pt选择194Pt+。氮化硼中的杂质元素含量可通过样品片中待测元素含量减去来自于铟薄片或钽勺中该元素贡献的含量来计算获得。将样品平行测定5次,相对标准偏差均在20%以内。对于Al、Si、Ti等元素的测定,3种制样方法的测定结果基本一致;方法1、方法2中检测到的In含量较大,使得铟中的Ni、Cu对氮化硼的测定值影响较大;方法3由于钽中Fe、Cu的贡献导致氮化硼中Fe、Cu的检测值较大,但方法3获得的基体信号强度大,可降低部分元素的检出限,如Cr、Mn、Ga、Ge等。综上所述,方法3为优选方法。 相似文献
66.
Haibo Zhang Guohua Geng Kang Li Cheng Liu Yuqing Hou 《Journal of Modern Optics》2018,65(20):2278-2289
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?1) regularization was utilized for the efficient reconstruction for early detection of small tumour in CB-XLCT imaging. Specifically, we transformed the non-convex optimization problem into an iteratively reweighted scheme based on the L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?1) model. We studied eight different non-convex p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?1/2) methods give the best performance. 相似文献
67.
《Calphad》2019
An overview of the research on silver-based (Ag-Sn, Ag-Cu, Ag-Ni) and nickel-based (Cu-Ni, Au-Ni, Ni-Pt) bimetallic nanoparticles is presented. The investigated nanoparticles in this review are formed by elements that represent an important group of metals revealing fcc lattice under macro-sized conditions (with the exception of Sn). The effects of surface stabilizing layer of the alloy nanoparticles are also described. Our experience with synthesis, characterization and stabilization of alloy nanoparticles is summarized. The development of the nanoparticle synthesis represents an important and mandatory part of the experimental nanoalloy research. Main synthetic routes under focus are the low temperature borohydride reduction method, the high temperature oleylamine synthesis, and the high pressure method in autoclave. The subsequent structural studies are focused on both nanoparticle core and outer stabilizing layer. The cores of the nanoparticles are studied mainly by electron microscopy techniques. The phase stability of the nanoparticle core is investigated by thermal analysis. The Knudsen effusion mass spectrometry was applied for studies of stabilizing organic molecules that can be found on the surface of the nanoparticles. The presented overview of the experimental results is complemented by thermodynamic calculations of phase diagrams by the CALPHAD method. 相似文献
68.
为研究高校既有建筑室内人群散发对室内VOCs的影响,对高校不同人群样本的教室及会议室两类典型人群密集房间,共82个人群样本对象进行了VOCs采样分析,得到不同实际场景下的人员相关的VOCs浓度水平,并对其潜在的影响因素进行分析。结果表明,共确认了29种与室内人员相关的高检出率且较高浓度值的物质,包括芳香族化合物9种,烷烯烃类9种,酮类和醛类8种,醇酯类以及卤化物3种,并得到主要VOCs物质的浓度水平和I/O比。对影响因素的统计分析表明,室内人员密度、季节和房间类型对不同VOCs物质存在显著性影响,其中季节性因素对目标VOCs污染物影响最为广泛,其次是房间类型与室内人员密度。该研究可为进一步了解人员密集室内VOCs污染现状及控制策略提供一定的科学参考。 相似文献
69.
Ponnusamy Nandha Kumar Shangavi Subramanian Uthirapathy Vijayalakshmi Sanjeevi Kannan 《Journal of the American Ceramic Society》2020,103(6):3528-3540
Structurally stable β-Ca3(PO4)2/t-ZrO2 composite mixtures with the aid of Dy3+ stabilizer were accomplished at 1500°C. The precursors comprising Ca2+, P5+, Zr4+, and Dy3+ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca3(PO4)2 occurred only at 1300°C, whereas the evidence of t-ZrO2 crystallization is obvious at 900°C. The dual occupancy of Dy3+ at β-Ca3(PO4)2 and t-ZrO2 structures was evident; however, Dy3+ initially prefers to occupy β-Ca3(PO4)2 lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO2. The typical absorption and emission behavior of Dy3+ were noticed in all the systems and, moreover, the surrounding symmetry of Dy3+ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy3+. A gradual increment in the phase content of t-ZrO2 in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions. 相似文献
70.
建立了一种快速、高效的QuEChERS-高效液相色谱-质谱联用法(QuEChERS-HPLC-MS/MS)测定谷类杂粮制品中脱氧雪腐镰刀菌烯醇(DON)、3-乙酰脱氧雪腐镰刀菌烯醇(3-ADON)、15-乙酰脱氧雪腐镰刀菌烯醇(15-ADON)和玉米赤霉烯酮(ZON)共4种真菌毒素。样品前处理采用乙腈-水溶剂提取,经Florisil+C18+无水硫酸镁净化后检测。以0.10%甲酸-乙腈作为流动相,在质谱检测器的多反应监测模式下进行分析。结果表明,4种真菌毒素在各自的线性范围内线性关系良好,相关系数R2均大于0.999,回收率在85.1%~102.0%,相对标准偏差(RSD)为2.11%~6.22%。该方法具有前处理简单、净化效果好、灵敏度高和检测速度快的优点,适用于谷类杂粮制品中DON、3-ADON、15-ADON 和ZON的分析和定量检测。 相似文献