Visualisation of interlaboratory comparison results in PomPlots

In this work a novel graphical method is applied to the presentation of intercomparison results. This is demonstrated with the results of a recent intercomparison in measuring the ¹³⁷Cs, ⁴⁰K, and ⁹⁰Sr activity concentration in milk powder. The “PomPlot”, an intuitive graphical method, is used for producing a summary overview of the participants’ results of a common measurand. The “PomPlot” displays (relative) deviations of individual results from the reference value on the horizontal axis and (relative) uncertainties on the vertical axis.     

Probe—detektor-anordnungen zur Kernstrahlungsmessung für Analytische Zwecke

The “analytical power” of detection systems is investigated, considering typical arrangements in analytical terms. From N atoms of interest in a sample Z counts are drawn: Z=R N (R registration yield). Crude data ZM contain also background U generated by interferences: ZM=Z+U. Identification and separation of Z is accompanied by errors ~σ_MU^1/2 due to imperfect distinguishability and to statistical error (σ_M model inherent factor). With “selectivity”=σ_M ^- (R/R_interference)^1/2 the figure of merit is G=selectivity efficiency/interference)^1/2. Sample background dominating, “interference” or both “interference” and “efficiency” have to be cancelled. Present semiconductor spectrometry of low energy γ-quanta and of large rates is not very far from its limits. Further progress will be obtained by enhancement of high energy efficiency and reduction of natural background.      

Theoretical study of the structure and stability of cage-substituted icosahedral closo-boranes, alanes, and gallanes MiM′12 ? iH 122? (M, M′ = B, Al, and Ga; i = 0–12)

The equilibrium geometric parameters and energetic and spectroscopic characteristics of low-lying conformers for several series of model cage-substituted (mixed) borane, alane, and gallane closo-dianions M _i M′_{12 − i} H₁₂²⁻(M, M′ = B, Al, Ga), as well as of “bare” gallium-aluminum anions Ga _i Al_12−i ⁻ with i = 0–12, were calculated within the B3LYP approximation of the density functional theory using 6–31G* and 6–311+G** basis sets. Differences in structure and stability between alanoborane clusters of similar composition are revealed. In clusters where the M and M’ heteroatoms are close in size and electronegativity (in gallonoalanes and gallium-aluminum anions), successive substitutions of M′ for M are accompanied by small energy changes and occur quasi-stochastically in different positions of the cage. When the substituents are significantly different (in alanoboranes), mixed clusters are unstable against disproportionation into homonuclear “predecessors” M₁₂H₁₂²⁻ and M′₁₂H₁₂²⁻, and the most favorable M _i M′_{12 − i} H₁₂²⁻ structures among them are those in which M _i M′_{12 − i} the cages are subdivided into homonuclear “subclusters” M _i and M′t′_12−i with a maximal number of homonuclear bonds (M-M and M′-M′) and a minimal number of heteronuclear bonds (M-M′).     

Interplay of thermochemistry and structural chemistry, the journal (volume 15, 2004) and the discipline

As practiced disciplines, structural chemistry, and thermochemistry need not necessarily be related. Yet such relationships, ranging from minor to very close, can help our overall understanding and detailed analyses of the species and methods under consideration. In the current study, these relations are made more evident from among the contents of the journal “Structural Chemistry” (Vol. 15) for the year 2004. The year’s articles have been reviewed, giving to most of those appearing therein a thermochemical commentary, “spin” or “slant.” A special emphasis is made on raising questions or noting possible future research topics that arise when looking at the relations noted earlier.     

The Si-doped planar tetracoordinate carbon (ptC) unit CAl<Subscript>3</Subscript>Si<Superscript>−</Superscript> could be used as a building block or inorganic ligand during cluster-assembly

Currently, the molecular assembly and growth from a small building block to the bulk compounds have become a focus in various fields. Ever being chemical curiosities, the “anti-van’t Hoff/Le Bel” realm that is associated with tetracoordinate or hypercoordiate planar centers has made vast progress. Being important in the fundamental research areas, the ptC species have potential applications in materials science. The existence of ptC in a divanadium complex and a large number of organometallic compounds have since been reported to possess ptC and these provide us with great hope that many more compounds with ptC building blocks may be synthesized in future. Herein, we report the assembly and stabilization of CAl₃Si⁻ in both the “homo-decked sandwich” and “hetero-decked sandwich” schemes at the B3LYP/6-311+G(d) level. We show that while the Si-doped indeed introduces much complexity during assembly, the electronic and structural integrity feature of CAl₃Si⁻ is well conserved during cluster-assembly, characteristic of a “superatom”. This study should be helpful in understanding the hetero-doped assembly mechanism of the ptC chemistry. Moreover, the present results are expected to enrich the flat carbon chemistry, superatom chemistry, metallocenes and combinational chemistry. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electrocatalytic activity of poly(3-methylthiophene) electrodes

Poly 3-methylthiophene (P3MT) modified electrodes have shown an improvement for detecting catecholamines when compared to classical ones. Past work with this polymer electrode suggested the possible presence of “active sites,” which are believed to be the polymer’s center of electrocatalytic activity. The interaction of 1,5-anthroquinone-disolfonic acid (1,5-AQDS) at the P3MT electrode showed a nonreversible behavior resulting in the blocking of “the active sites,” suggesting the specific electcatalytical activity of this polymer is limited to catechol and similar compounds. In order to improve catecholamine detection, two methods of electropolymerization for P3MT were compared under similar conditions; (1) a constant potential for a specific length of time, and (2) potential cycling. It was found that cycling provided a more sensitive CV, i.e. increased number of active sites. Under a controlled pH study (pH range 2–9), the polymer electrode maintained its superior performance, manifested as lower ΔE and higher i, toward catechol over the traditional electrodes. Two different supporting electrolytes were used, sulfate and phosphate, and it was found that in neutral or basic solutions containing phosphate, the oxidation and reduction potentials of catechol shifted to lower values. Solutions containing sulfate exhibited no shift in the oxidation potential at any pH value.     

Visualisation of proficiency test exercise results in Kiri plots

A novel graphical method (‘Kiri plots’) for the presentation of proficiency test exercise results is presented. The Kiri plot visualises the evaluation of the proficiency test results based on three statistical tests (the z score, the zeta score and the relative uncertainty outlier test) by defining six zones including a central “in agreement” zone.     

The kinetics and main pathways for the liquid-phase oxidation of cyclohexene by air in the presence of cobalt,chromium, iron,and nickel µ<Subscript>3</Subscript>-oxotrimetallohexapivalates

It was found that during the liquid-phase oxidation of cyclohexene (CH) by air (323–343 K) in the presence of a series of homo-and heteronuclear μ ₃-oxotrimetallohexapivalates with a M₂M′O (M, M′ = Co, Cr, Fe, Ni) core insignificant amounts of the corresponding epoxide are formed, and 3-hydroperoxy-2-cyclohexene (HP), 3-hydroxy-2-cyclohexene (CHol), and 2-cyclohexen-3-one (CHone) accumulate in the oxidate. It is suggested that CHone and CHol are “dead-end” products from the oxidation of CH under the investigated conditions while the HP is a unique “intermediate-damper” that gives rise to the realization of alternative paths (catalytic cycles) for the formation of these products. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 85–90, March–April, 2007.     

Effect of the nature of an organoaluminum activator on catalytic properties of phenoxyimine zirconium complexes in homo- and copolymerization reactions of ethylene

Catalytic properties of the phenoxyimine zirconium complexes, viz., bis[N-(3,5-di-tert-butylsalicylidene)anilinato]zirconium(IV) dichloride (1) and its fluorinated analog, bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]zirconium(IV) dichloride (2), were studied. Ethylene homopolymerization and copolymerization of ethylene with α-olefins were chosen as catalytic reactions, and various organoaluminum compounds served as activators: commercial polymethylalumoxane (MAO) containing ∼35 mol.% of trimethylaluminum (TMA), MAO purified from TMA (“dry” MAO), and “classical” organoaluminum compounds, namely, TMA and triisobutylaluminum (TIBA). Complex 1 is not activated by “dry” MAO but is efficiently transformed into the catalytically active state by commercial MAO, “conventional” TMA, and TIBA. These processes give low-molecular-weight polyethylenes (PE) characterized by high values of polydispersity indices and by polymodal curves of gel permeation chromatography (GPC). The order of decreasing the efficiency of activation for the cocatalysts is MAO > TIBA > TMA. Fluorinated complex 2 exhibits a high activity after its treatment with MAO and “dry” MAO, the activity is much lower upon mixing with TIBA, and complex 2 is inactive when using TMA. In the copolymerization of ethylene with hex-1-ene and dec-1-ene, complex 1 treated with MAO is highly active but gives a low level of insertion of the comonomer (1–2 mol.% in the copolymer). Complex 2 activated with “dry” MAO is more efficient in the copolymerization of ethylene with propylene or hex-1-ene but, like complex 1, it does not produce copolymers with a high content of the comonomer. The both catalysts provide the insertion of α-olefin as isolated units separated by extended sections of the chain consisting of ethylene units.     

A study on mass spectrometry of methylated [60] fullerenes using the “in-beam” electron impact technique

Mass spectra of the methylated [60]fullerenes were obtained by EI mass spectrometry using “desorption” or “in-beam” technique. The mass spectra of the methylated fullerenes, C₆₀Me_n, have the molecular ion peak M⁺ indicating that the product is stable under the MS (EI) conditions. The appearance of an intense peak at m/z 360 was assigned to the formation of fullerene dication C₆₀⁺⁺. The remaining peaks were assigned to successive loss of methyl groups from molecular monocation and dication.     

Evaluation of a new generation quadrupole-based ICP-MS for uranium isotopic measurements in environmental samples

We compare the analytical performance of a modern quadrupole-based ICP-MS (“X-Series”, Thermo-Electron, Winsford, UK) with a single-collector double-focusing sector-field ICP-MS (“Axiom”, VG Elemental, Winsford, UK) for uranium isotopic measurements in environmental samples. We focus on the precision and accuracy obtained with both instruments for the ²³⁵U/²³⁸U isotopic ratios and on the abundance sensitivity that is a key parameter for low ²³⁶U/²³⁸U isotopic ratios measurements. We observe that isotopic measurements are more precise accurate with the “X-Series” than with the “Axiom”. Besides, we demonstrate that the “Axiom’s” higher abundance sensitivity limits its capability to measure ²³⁶U/²³⁸U ratio below a few ppm.     

Towards more fair and effective doping tests based on chromatography with mass spectrometric detection

Van Eenoo and Delbeke in Accred Qual Assur (2009) have criticized Faber (in Accred Qual Assur, 2009) for not taking “all factors under consideration when making his claims”. Here, it is detailed that their criticism is based on a misunderstanding of examples that were merely intended to be illustrative. Motivated by this criticism, further discussion is provided that may help in the pursuit of more fair and effective doping tests, here exemplified by chromatography with mass spectrometric detection. Surely, any doping test can only be improved or even optimized if the risks of false positives and false negatives are well defined. This requirement is consistent with a basic principle concerning mathematical approximations (Parlett in “The symmetric eigenvalue problem”, Prentice-Hall, Englewood Cliffs, 1980): apart from just being good, they should be known to be good. Author’s reply to the response on “Regulations in the field of residue and doping analysis...” Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Linearly polarized white fluorescence from shish-kebab type liquid crystalline poly(P-phenylenevinvlene)s with (P-phenylene)s as kebab

Liquid crystalline(LC) polymers with a shish-kebab-type moiety on their cross-conjugated(p-phenylene)s-poly(p-phenylenevinylene) s main chains were synthesized through Gilch polymerization in order to develop a kind of polymers available for linearly polarized white-light-emitting from single chain.In this system,the 2,5-bis(4’-alkoxyphenyl)benzene as the "kebabs" connects with poly(p-phenylenevinylene)(PPV) main chain backbone using its molecular gravity center and the PPV as the "shish" or "skewer"(the "shish-kebab").The polymers possess desirable properties such as excellent solubility and liquid crystalline properties.To drop the "kebabs" of the 2,5-bis(4’-alkoxyphenyl)benzene into the orientation microgroove of aligned polyimide film,not only the "shish" of polymer main chain can be aligned by the virtue of orientation of "kebabs" but also the uniform cross-conjugated structure between the "kebabs" and "shish" can be broken. Then,the alignment of the polymer main chain showed yellow light emission and was also accompanied by orientation of the LC side chains showing blue light emission,this gave rise to a notable linearly polarized white fluorescence.     

Modern aspects on tri- and tetranuclear cluster complexes supported by phosphido bridges

This report on small cluster complexes with metal-metal bonds in the field of coordination chemistry documents results in the following scientific areas. (1) Systematic synthetic routes via ditransition metal carbonyl derivative of manganese and rhenium (group 7) to functionalizedtriangulo- andtetrahedro-clusters including structural characterization, (2) Dynamic properties of mono- and diauration isomers like M₂(μ-AuPR₃)(μ-PCyH)(CO)₈/M₂(μ-H)(μ₃-PCy(AuPR₃))(CO)₈ (isomerization) and M₂(μ-AuPR₃)₂(μ₄-PCy)(CO)₈/M₂(μ-AuPR₃)(μ₃-PCy(AuPR₃))(CO)₈ (M = Mn, Re; R = organic residue) (rearrangement and valence isomerization) and MM’(μ-H)(μ-PCy₂)(μ₄-PCy(AuPR₃))(CO)₆ (M = M’, M ≠ M’) (topomerization) going from one to the other homologue and the kinetic study of isomerization in the framework Re₂(AuPCy₃)₂(μ-PMeN₂(μ-C(Bu)O)(CO)₆, (3) Correlations of chirality transfer in diastereomerictetrahedro-clusters Re₂(M¹PR₃)₂(μ-PCy₂)(CO)₇(η¹-L*) (M¹ = coin metals, L* = chiral ligand as (+) or (-) prolinate, for example) from CD data. These selected contributions will be discussed to answer the question “Do small cluster complexes remain as a future challenge in cluster chemistry?”     

Metrology and protometrology: the ordinal question

Laboratory medicine provides results for quantities as well as for properties having no magnitude. The terminology of the latter is less well established and sources are contradictory. Two recent papers on “protometrology” published in this journal offer an opportunity to discuss the necessary concept systems. The delineations of “metrology” versus “protometrology”, “observation” versus “measurement”, and the generic division of “property” are examined with emphasis on avoiding conflict with the International Vocabulary of Metrology. It is suggested that having “examination” as a top generic concept coupled with systematic modifiers for division, especially ‘nominal’ and ‘ordinal’, is a preferable terminological solution.

Distances and volumina for graphs

It has long been realized that connected graphs have some sort of geometric structure, in that there is a natural distance function (or metric), namely, the shortest-path distance function. In fact, there are several other natural yet intrinsic distance functions, including: the resistance distance, correspondent “square-rooted” distance functions, and a so‐called “quasi‐Euclidean” distance function. Some of these distance functions are introduced here, and some are noted not only to satisfy the usual triangle inequality but also other relations such as the “tetrahedron inequality”. Granted some (intrinsic) distance function, there are different consequent graph-invariants. Here attention is directed to a sequence of graph invariants which may be interpreted as: the sum of a power of the distances between pairs of vertices of G, the sum of a power of the “areas” between triples of vertices of G, the sum of a power of the “volumes” between quartets of vertices of G, etc. The Cayley–Menger formula for n-volumes in Euclidean space is taken as the defining relation for so-called “n-volumina” in terms of graph distances, and several theorems are here established for the volumina-sum invariants (when the mentioned power is 2). This revised version was published online in July 2006 with corrections to the Cover Date.     

Bacteriophage SPZ7 endolysin: The influence of effectors on the lytic activity of the enzyme on the lysis of gram-negative microorganisms

The possibilities of bacteriophage SPZ7 endolysin functioning in the lysis of gram-negative bacteria “from without” were studied. A significant 1.5–3-fold increase in bacteriophage SPZ7 endolysin activity during the lysis of S. enteritidis N60 and E. coli TG1 cells in the presence of high-molecular surfactants, pluronics with a large hydrophobic block, hen’s egg lysozyme, and low concentrations of a peptide antibiotic (colistin), was shown. The developed approach may be promising for improving the efficiency of pharmaceutical bacteriophage enzyme-based antibacterials working against gram-negative microorganisms.     

Radiological characterization of commercially available “radon spa sources”

Nowadays, artificial “radon spa sources” for home baths are commercially available. Although these sources could give a potential radiation exposure to the users, few studies have been reported on their radiological measurements. In the present study, five types of radon spa sources were collected and their radiological characterization was investigated. The followings were estimated for these samples: (1) radon emanation coefficients (dry and water-saturated conditions), (2) surface γ-ray dose rate, (3) surface count rates for α- and β-rays, (4) activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, and (5) concentrations of radon and thoron generated from the sources located in an air flow system. The activity concentrations were very high (except for one sample (named “sample B”), although radon emanation coefficient was low compared with soil. This leads to high concentrations of radon/thoron generated from the sample. The maximum surface γ-ray dose rate was observed for sample A (2.7 μGy h⁻¹). If people stay very close to the sample for a long time, the exposure might be significant.