Uncertainty of chemical oxygen demand determination in wastewater samples

 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     

Three New Lignan Derivatives from Lindera glauca (Siebold et Zucc.) Blume

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.     

Two New Cytotoxic Spirostane‐Steroidal Saponins from the Roots of Bletilla striata

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 .     

Proton transfer reactions for improved peptide characterisation

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).     

Σatomic states and the nucleon distribution in Pb

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.     

Molecular speciation of microparticles: application of pattern recognition techniques to laser microprobe mass spectrometric data

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.     

Kinetics of decomposition pathways of an energetic GZT molecule

This investigation uses the Gaussian 98 program, density functional theory (DFT) B3LYP/6‐31G(d,p), and ab initio MP2/6‐31G(d,p) and HF/6‐31G(d) methods to model energetic diguanidinium 5,5′‐azotetrazolate (GZT) ionic species in order to determine their decomposition mechanisms. GZT was initially cracked into two guanidinium cations (G⁺) and a 5,5′‐azotetrazolate anion (ZT^2?). Three routes—the elimination of a hydronium ion (H⁺), the elimination of a hydrogen radical (H·), and the elimination of an amine radical (·NH₂)—are suggested for the decomposition of the G⁺ cation, and three routes—single ring opening, double ring opening and N? N bond cleavage outside the ring—are proposed for the further decomposition of the ZT^2? anion. Fourteen decomposition species were obtained on splitting both the cation and anion. This result reveals the reliability of the aforementioned decomposition mechanisms. The transition state species were also obtained using a two‐structure or three‐structure synchronous transit‐guided quasi‐Newton (STQN) between the Cartesian coordinates of related particles at specific decomposition stages in this research. The corresponding activation energies in all decomposition stages were considered to infer the most feasible pathways of GZT decomposition. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Solid phase synthesis of benzamidine and butylamine-derived hydantoin libraries

We have constructed a number of benzamidine- and butylamine-based hydantoin compounds by means of an efficient route using solid phase synthesis in which neat diisopropylamine was employed for a novel cyclization/traceless cleavage step. All library compounds were obtained in excellent yield and high purity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Improved methods for supergraphs

We introduce some new techniques into superfield perturbation theory which allow considerable simplifications in calculations. As a result, we show that all contributions to the effective action can be written as integrals over a single d⁴θ. We also give the background group field formalism for supersymmetric non-abelian gauge theories. To illustrate our methods, we give examples of loop calculations: in particular, we show that in O(4) extended supersymmetric non-abelian gauge theories all one-loop propagator corrections cancel identically (both infinite and finite parts) and that these theories, at one loop, are finite and have no renormalizations (in the Fermi-Feynman gauge).