Metrological role of neutron activation analysis. III. Role of INAA in sampling behavior characterization

The minimum sample size, usually 100 mg or larger, is often the only information given on certificates of existing certified reference materials (CRMs) to describe sampling behavior. This value is not only too large for quality control requirements of microanalysis, but also too general to reflect the strong element-specific nature of the sampling behavior of solid materials. In this paper, the third and final of the series, we explain the need for CRMs with sampling behavior characterized for individual elements and describe the unique role of instrumental neutron activation analysis in sampling behaviour characterization. Received: 19 March 2001 Accepted: 2 October 2001     

A new certified reference material for the quality control of palladium, platinum and rhodium in road dust, BCR-723

Certified Reference Materials (CRMs) represent a key tool for the quality control of chemical analyses. The demand for environmental materials is constantly increasing in complex analytical fields, and the European Commission (EC) (through the Measurements & Testing Generic Activity) is responding to the urgent needs for materials requiring collaborative efforts at the international level. This paper describes the preparation of a new road-dust material (BCR-723), along with homogeneity and stability studies and the analytical work performed for the certification of the contents of palladium, platinum and rhodium, under the EC's PACEPAC project, PACEPAC being the acronym for “Production And CErtification of a road dust reference material for Platinum, palladium and rhodium used in Automotive Catalytic converters”.     

利用二氧化钛静电纺丝和透明质酸甲基丙烯酸酯构筑用于细胞培养的纤维凝胶结构

通过观察生物体内骨的电镜图片,发现骨表面具有丰富的纤维微纳结构,在此观测的启发下,本实验设计将二氧化钛表面生物活性化的同时构筑这种纤维微纳结构,模仿骨表面。考虑到二氧化钛具有光催化性,且具有生物无毒性,本实验采用"自上而下"的一步法,在紫外光照的条件下,将二氧化钛静电纺丝与透明质酸衍生物在光照条件下通过双键稳定地连接起来。傅立叶-红外光谱分析表明实验成功地在二氧化钛静电纺丝表面嫁接上透明质酸分子。通过荧光和扫描电镜分析表明,间充质干细胞可以很好地在二氧化钛静电纺丝和透明质酸的复合结构上生长。这种构筑复合结构表面的方法,生物活化了二氧化钛纺丝的表面,同时模仿骨表面获得了微纳纤维拓扑结构。此外,可以将二氧化钛静电纺丝纺在不同种类的材料表面,从而在不同材料表面简便地得到可用于细胞培养的纤维表面结构,对于未来可实际应用的移植材料研发具有很好的借鉴意义。     

便携式近红外光谱仪对废旧涤/棉混纺织物中涤含量的快速检测

利用近红外光谱技术对252个涤/棉混纺织物进行研究,建立了不同光谱特征的涤/棉混纺织物的偏最小二乘(PLS)定量分析模型。将近红外光谱异常样本与光谱正常样本分别建模,显著提高了定量分析模型的预测精度、拓宽了模型的适用范围。以涤、棉主要吸收峰区间为基本建模波段,进行双向扩展,筛选出最佳建模波段,以相关系数(R)、预测集标准差(SEP)和验证集准确率优化建模条件,并与未分别建模的PLS模型相比较。用346个未参与建模的废旧涤/棉混纺织物对模型进行外部验证,外部验证准确率为92%,识别时间8s。     

传统文化融入中学化学教学——“非遗印染技艺”的教学资源开发

从染料的利用历史、传统印染工艺、印染环保创新等3个维度挖掘了非遗印染技艺的教学资源,与萃取、自然资源开发利用、还原剂、硫及其化合物、酚醇性质、配合物、电解池等化学知识结合,以印染技艺为载体将传统文化、思政教育与化学教学有机融合,落实化学学科核心素养的发展,为传统文化融入中学化学教学提供借鉴。     

Key requirements for introducing quality assurance in measurement laboratories

 The implementation of a quality assurance system is fraught with difficulties. However, these difficulties may be overcome if the laboratory uses suitable means to facilitate the process. It is necessary to mobilise the intelligence and energy of all members of the laboratory. In order to command adherence, the project must be shared, and this necessitates a major effort by all concerned. Communication is a major factor in obtaining the support of all parties. Six important steps must be distinguished: – Defining quality policy – Creating awareness, information, training – Creating a quality structure – Establishing a deadline for obtaining accreditation – Progressive implementation – Experimentation and validation. Even if the task of obtaining and maintaining accreditation remains difficult, it clearly promotes a minimum level of organisation and stepwise progress in quality assurance. The laboratory must keep improving its quality system, using European Standard EN 45001 as an effective management model. Received: 9 April 1997 · Accepted: 11 September 1997     

Acetamide degradation by a continuous-fed batch culture ofBacillus sphaericus

Applied Biochemistry and Biotechnology - The methanogenesis of acetamide occurs through a two-step reaction in methanogenic sludges. First, acetamide is hydrolyzed to acetate and ammonia by a...     

Cofermentation of glucose,xylose, and arabinose by mixed cultures of two genetically engineeredZymomonas mobilis strains

Cofermentation of xylose and arabinose, in addition to glucose, is critical for complete bioconversion of lignocellulosic biomass, such as agricultural residues and herbaceous energy crops, to ethanol. A factorial design experiment was used to evaluate the cofermentation of glucose, xylose, and arabinose with mixed cultures of two genetically engineeredZymomonas mobilis strains (one ferments xylose and the other arabinose). The pH range studied was 5.0-6.0, and the temperature range was 30-37°C The individual sugar concentrations used were 30 g/L glucose, 30 g/L xylose, and 20 g/L arabinose. The optimal cofermentation conditions obtained by data analysis, using Design Expert software, were pH 5.85 and temperature 31.5°C. The cofermentation process yield at optimal conditions was 72.5% of theoritical maximum. The results showed that neither the arabinose strain nor arabinose affected the performance of the xylose strain; however, both xylose strain and xylose had a significant effect on the performance of the arabinose strain. Although cofermentation of all three sugars is achieved by the mixed cultures, there is a preferential order of sugar utilization. Glucose is used rapidly, then xylose, followed by arabinose.     

Enhancement of pullulan production by aureobasidium pullulans in batch culture using olive oil and sucrose as carbon sources

The production of pigment-free pullulan byAureobasidium pullulans, using olive oil and sucrose as carbon (C) sources, in shake flasks, was investigated. Optimum medium composition for pullulan elaboration was 80 g/L sucrose, 25 mL/L olive oil, 5 mL/L Tween-80, 10 g/L glutamic acid, and an initial pH of 5.5. Maximum pullulan concentration (51.5 g/L), productivity (8.6 g/L·d), and yield (80.3%) were achieved under these conditions after 120 h of fermentation. The principal advantage of using olive oil and sucrose simultaneously as C sources was the elimination of the inhibitory effect of high sucrose concentrations (> 60 g/L) on pullulan production by the microorganism. Structural characterization by¹³C-NMR, monosaccharide, and methylation analyses, and pullulanase digestion, combined with size-exclusion chromatography, confirmed the identity of pullulan and the homogeneity of the released polysaccharide in the fermentation broths. There were no significant differences in structure between pullulan samples isolated from either olive oil-supplemented media or olive oil-free media. The molecular size of pullulan from the combined olive oil-sucrose fermentation was slightly lower (1.1 X 10⁶) than that of conventional fermentation with sucrose as a single C source (1.4 X 10⁶). Lowering the initial pH of the medium resulted in increased molecular size for the released polymer, but a lower pullulan yield.