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51.
The measurement uncertainty of the result of chemical oxygen demand determination in wastewater was evaluated. The major
sources of uncertainty of the result of measurement were identified as the purity of reagents, volumetric operations, gravimetric
operations, bias, and the repeatability of the method. Identification and evaluation of uncertainty sources was followed by
combined uncertainty calculations. The combined uncertainty was compared to the experimentally determined variation and good
agreement was found, indicating that the major uncertainty sources had been identified. The results show that the major sources
of uncertainty arose from repeatability at high concentration level and volumetric steps at low concentration level, thus
revealing the target operations for reducing the measurement uncertainty of this determination.
Received: 5 August 2002 Accepted: 5 November 2002
Acknowledgements This research was supported by the Ministry of Education, Science and Sport of the Republic of Slovenia (Project Z2–3530).
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials
in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to A. Drolc 相似文献
52.
The surface area of nanosized agglomerates is of great importance as the reactivity and health effects of such particles are
highly dependent on surface area. Changes in surface area through sintering during nanoparticle synthesis processes are also
of interest for precision control of synthesised particles. Unfortunately, information on particle surface area and surface
area dynamics is not readily obtainable through traditional particle mobility sizing techniques. In this study, we have experimentally
determined the mobility diameter of transition regime agglomerates with 3, 4, and 5 primary particles. Agglomerates were produced
by spray drying well-characterised polystyrene latex particles with diameters of 55, 67, 76, and 99 nm. Tandem differential
mobility analysis was used to determine agglomerate mobility diameter by selecting monodisperse agglomerates with the same
number of primary particles in the first DMA, and subsequently completely sintering the agglomerates in a furnace aerosol
reactor. The size distribution of the completely sintered particles was measured by an SMPS system, which allowed for the
determination of the number of primary particles in the agglomerates. A simple power law regression was used to express mobility
diameter as a function of primary particle size and the number of primary particles, and had an excellent correlation (R2 = 0.9971) with the experimental data. A scaling exponent was determined from the experimental data to relate measured mobility
diameter to surface area for agglomerates. Using this relationship, the sintering characteristics of agglomerates were also
examined for varying furnace temperatures and residence times. The sintering data agreed well with the geometric sintering
model (GSM) model proposed by Cho & Biswas (2006a) as well as with the model proposed Koch & Friedlander (1990) for sintering by viscous flow. 相似文献
53.
Won Se Suh Ki Hyun Kim Ho Kyung Kim Sang Un Choi Kang Ro Lee 《Helvetica chimica acta》2015,98(8):1087-1094
Two new aryl‐tetralin lignan glycosides, linderanosides A and B ( 1 and 2 , resp.), and a new dihydrobenzofuran neolignan glycoside, linderanoside C ( 3 ), together with five known lignan derivatives ( 4 – 8 ) were isolated from the trunk of Lindera glauca. The structures of these new compounds were determined through spectroscopic analyses, including extensive 2D‐NMR data and acid hydrolysis. The absolute configurations of the compounds were clarified by circular dichroism (CD) spectroscopic studies. Compounds 1 – 8 were evaluated for their cytotoxicity against A549 (non‐small cell lung adenocarcinoma), SK‐OV‐3 (ovarian cancer cells), A498 (human kidney epithelial cells), and HCT‐15 (colon cancer cells) human tumor cell lines using sulforhodamine B assays in vitro. 相似文献
54.
Calix[4]arene-based cation receptor 1 has been synthesised by following a multi-step synthetic procedure. The fluorescence properties of 1 upon the addition of various metal ions were investigated by fluorescence spectroscopy. As a result, it was revealed that 1 displayed dramatic quenching effect upon the exposure to Cs+. In contrast, no significant quenching effects were observed upon the addition of other metal ions such as Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Ag+, Zn2+ and Ni2+. Compound 1 was also found by Job plot to form a 1:1 complex with Cs+. In addition, we also prepared 1-embedded electrospun nanofibrous film (NF-1) as an adsorbent for Cs+. NF-1 is proved to adsorb Cs+ effectively from an aqueous solution, indicating that it would be usefully utilised as an adsorbent to remove Cs+. 相似文献
55.
Jong Eel Park Kyeong Wan Woo Sang Un Choi Je Hyun Lee Kang Ro Lee 《Helvetica chimica acta》2014,97(1):56-63
Two new spirostane‐steroidal saponins, bletilnoside A ( 1 ) and bletilnoside B ( 2 ), together with five known compounds, 3 – 7 , were isolated from the roots of Bletilla striata (Thunb .) Reichb . F. The structures of the new compounds were determined based on their 1D‐ and 2D‐NMR spectral data. The isolated compounds 1 – 7 were tested for cytotoxicity against four human tumor cells (A549, SK‐OV‐3, SK‐MEL‐2, and HCT15) in vitro using a sulforhodamin B bioassay, and compounds 1, 2 , and 5 showed significant cytotoxicities against all tested tumor cell lines with IC50 values ranging from 3.98±0.16 to 12.10±0.40 μM . 相似文献
56.
Mingshi Jin Jung-Nam Park Jeong Kuk Shon Zhenghua Li Min Young Yoon Hyun Jung Na Young-Kwon Park Ji Man Kim 《Research on Chemical Intermediates》2011,37(9):1181-1192
Highly ordered mesoporous cerium dioxide (meso-CeO2) was successfully synthesized using a facile solvent-free infiltration method from a mesoporous silica template, KIT-6. The
meso-CeO2 material, thus obtained, exhibited well-defined mesostructure and high surface area (153 m2 g−1). The physicochemical properties of meso-CeO2 material and Pd-supported on meso-CeO2 (Pd/meso-CeO2) were characterized by electron microscopy, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed experiments. The Pd/meso-CeO2 catalyst exhibited excellent catalytic activity for CO oxidation compared with those of other Pd/CeO2 catalysts which were prepared using nanocrystalline CeO2 and bulk-CeO2 as the supports. Moreover, a hydrogen pretreatment of the Pd/meso-CeO2 catalyst resulted in a remarkable increase of catalytic activity (T
100 = 52 °C). 相似文献
57.
The combination of deprotonation (via ion/molecule and ion/ion reactions) and low-energy collision-induced dissociation (CID) has been explored for the enhanced characterisation of tryptic peptides via access to different precursor charge states. This approach allows instant access to fragmentation properties of singly and doubly protonated precursors (arising from the availability of mobile protons) in a single experiment. Considering both charge states extended our base of structurally informative data (in comparison with considering just a single charge state) due to generation of additional sequence ions and by obtaining supplementary structural information derived from selective cleavages. Roughly 37% of combined data sets (CID spectra of doubly and singly charged precursor) showed a greater database identification confidence than each set alone. Moreover, comparison between a number of sequence ions of the singly charged precursor and the doubly charged precursor provided a mean of distinguishing the two classes of tryptic peptides (arginine or lysine containing). 相似文献
58.
Jennifer S.K. Chan Anthony Y.C. Kuk Carrie H.K. Yam 《Journal of multivariate analysis》2005,94(2):300-312
Geyer (J. Roy. Statist. Soc. 56 (1994) 291) proposed Monte Carlo method to approximate the whole likelihood function. His method is limited to choosing a proper reference point. We attempt to improve the method by assigning some prior information to the parameters and using the Gibbs output to evaluate the marginal likelihood and its derivatives through a Monte Carlo approximation. Vague priors are assigned to the parameters as well as the random effects within the Bayesian framework to represent a non-informative setting. Then the maximum likelihood estimates are obtained through the Newton Raphson method. Thus, out method serves as a bridge between Bayesian and classical approaches. The method is illustrated by analyzing the famous salamander mating data by generalized linear mixed models. 相似文献
59.
The analyses of (K-,π) and (π-, K+) reactions indicate that the nuclear potential of the Σ-hyperon is repulsive inside the nucleus, in agreement with the prediction of model F of the Nijmegen baryon-baryon interaction. This is consistent with the recent calculation of the strong-interaction shifts and widths of the observed levels of Σ- atoms, including the precise data on the Σ-Pb atom. In this paper, the sensitivity of this calculation to the neutron and proton density distributions is used to determine these densities in 208Pb. 相似文献
60.
Attempts were made to enhance the ability of laser microprobe mass spectrometry (LAMMS) to identify molecular species in individual microparticles by applying pattern recognition methods. Principal component analysis (PCA) and canonical discriminant analysis were applied to LAMMS data for nickel-containing environmental particles. Detailed comparison of the two statistical methods demonstrated the utility of PCA. The successful application was highly dependent on the use of appropriate spectral normalization and feature extraction techniques prior to PCA. Although the test system involved only a small number of standard compounds, the LAMMS data were complicated by the effects of intra-particle heterogeneity common to environmental samples and by instrumental limitations. Pattern recognition techniques provided more accurate quantitative assignments of molecular species than were available by qualitative inspection of characteristic cluster ions or by simple spectral subtraction to compare particle data with a library of standard compounds. Results were substantiated by comparison with bulk analysis studies using wet chemical techniques. 相似文献