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991.
The use of (certified) reference materials and quality control materials can form a suitable basis for evaluating measurement uncertainty of routine measurements. In particular when these materials are used for quality control purposes, it is not always evident how the quality control data can be used in the uncertainty budget of a routine measurement. Current guidance documents on the evaluation of measurement uncertainty and the use of reference materials treat this subject only in part, or in very generic terms. ISO/REMCO has established a new working group that will provide practical guidance and examples on how to use quality control data in the evaluation of measurement uncertainty. A short introduction to the subject is given.
相似文献
Adriaan M. H. van der VeenEmail: Phone: +31-15-2691733Fax: +31-15-2691670 |
992.
Ashish Surya?Prakash?Singh Ashok?Kumar?Singh Bharat?SinghEmail author 《Transition Metal Chemistry》2005,30(5):610-615
Kinetics and mechanism of the Os(VIII) catalysed oxidation of crotonic acid (CA) by KBrO3 in alkaline medium have been investigated. Zero order dependence in [KBrO3] was observed, while first order with respect to CA in its lower concentration range tends to zero order at its higher concentration range. The order in [Os(VIII)] was found to be unity and a positive effect of [OH−] was observed. Variation of the ionic strength (μ) and dielectric constant of the medium and addition of Hg(OAc)2 (used as Br− scavenger) had an insignificant effect on the rate of reaction. Thermodynamic parameters have also been calculated and reported. A suitable mechanism consistent with the observed kinetic results has been suggested and the related rate law deduced. 相似文献
993.
Marcelo O. Santiago Alzir A. Batista Marcio P. de Araújo Claudio L. Donnici Icaro de S. Moreira Eduardo E. Castellano Javier Ellena Sauli dos Santos Jr Salete L. Queiroz 《Transition Metal Chemistry》2005,30(2):170-175
A series of cis-{RuCl2(PPh3)2[4,4-(X)2-2,2-bipy]} [cis-chlorines; X=-H, -Me, -SMe, and (-Cl,-Me)] complexes have had their structures determined by single crystal X-ray diffraction. The geometry of these complexes, also determined in CH2Cl2 solution by 31P{1H}-n.m.r. spectroscopy, showed that the chemical shifts for the phosphorus atoms are slightly dependent on the pKa of the 4,4-(-X)2-2,2-bipy ligands. 相似文献
994.
Lucia?MutihacEmail author Hans-Jürgen?Buschmann Radu-Cristian?Mutihac Eckhard?Schollmeyer 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1-2):1-10
The ability of calix[n]arenes to form complexes, to act as extractants in liquid–liquid extraction, and run as carriers in transport through liquid membranes of different biological amine compounds (e.g., ammonium ion, amines, amino acids, and peptides) has been the central topics of many reports. These features recommend the calix[n]arenes as competitive candidates for studying the interactions involved in host–guest recognition as well as useful receptors in separation processes. Some specific aspects of their applications in binding and separation of various amine compounds by extraction, and in transport through liquid membranes have therefore been considered. The effect of the factors that might influence the separation of above compounds by extraction, and the transport through liquid membranes using the calix [n]arenes has been presented.This revised version was published online in July 2005 with a corrected issue number. 相似文献
995.
Hsu FF Turk J Rhoades ER Russell DG Shi Y Groisman EA 《Journal of the American Society for Mass Spectrometry》2005,16(4):491-504
We report negative-ion electrospray tandem mass spectrometric methods for structural characterization of cardiolipin (CL), a four-acyl-chain phospholipid containing two distinct phosphatidyl moieties, of which structural assignment of the fatty acid residues attached to the glycerol backbones performed by low-energy CAD tandem mass spectrometry has not been previously described. The low-energy MS2-spectra of the [M - H]- and [M - 2H]2- ions obtained with ion-trap or with tandem quadrupole instrument combined with ion-trap MS3-spectra or with source CAD product-ion spectra provide complete structural information for CL characterization. The MS2-spectra of the [M - H]- ions contain two sets of prominent fragment ions that comprise a phosphatidic acid, a dehydrated phosphatidylglycerol, and a (phosphatidic acid + 136) anion. The substantial differences in the abundances of the two distinct phosphatidic anions observed in the MS2-spectra of the [M -H]- ions lead to the assignment of the phosphatidyl moieties attached to the 1' or 3' position of central glycerol. Upon further collisional dissociation, the MS3-spectra of the phosphatidic anions provide information to identify the fatty acyl substituents and their position in the glycerol backbone. The MS2-spectra of the [M - 2H]2- ions obtained with TSQ or ITMS contain complementary information to confirm structural assignment. The applications of the above methods in the differentiation of cardiolipin isomers and in the identification of complex cardiolipin species consisting of multiple molecular structures are also demonstrated. 相似文献
996.
Koralewicz Maria Pruchnik Florian P. Szymaszek Anna Wajda-Hermanowicz Katarzyna Wrona-Grzegorek Katarzyna 《Transition Metal Chemistry》1998,23(4):523-525
The dimeric rhodium(II) complexes [Rh2(leu)4(H2O)2]- (ClO4)4 and [Rh2(pro)4(H2O)2](ClO4)4 have been prepared and characterized by elemental analyses, i.r., u.v.–vis. and 1H-n.m.r. spectroscopy. The amino acid molecules are coordinated as bridging ligands via their carboxylato groups. Cyclic voltammetry in DMF has shown that the complexes undergo a quasi-reversible reduction to yield dimers containing a Rh
2
3+
core. Oxidation processes within the 0–1.5V range were not observed. 相似文献
997.
Badman ER Myung S Clemmer DE 《Journal of the American Society for Mass Spectrometry》2005,16(9):1493-1497
The folding pathways of gas-phase cytochrome c ions produced by electrospray ionization have been studied by an ion trapping/ion mobility technique that allows conformations to be examined over extended timescales (10 ms to 10 s). The results show that the +9 charge state emerges from solution as a compact structure and then rapidly unfolds into several substantially more open structures, a transition that requires 30-60 ms; over substantially longer timescales (250 ms to 10 s) elongated states appear to refold into an array of folded structures. The new folded states are less compact than those that are apparent during the initial unfolding. Apparently, unfolding to highly open conformations is a key step that must occur before +9 ions can sample more compact states that are stable at longer times. 相似文献
998.
Archika?C.?Barve Smita?Ghosh Anupa?A.?Kumbhar Avinash?S.?KumbharEmail author Vedavati?G.?Puranik 《Transition Metal Chemistry》2005,30(3):312-316
The DNA binding characteristics of mixed ligand complexes of the type [Co(en)2(L)]Br3 where en = N,N′-ethylenediamine and L = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 1,10-phenanthroline-5,6-dione (phendione), dipyrido[3,2-a:2′,3′-c]phenazine (dppz) have been investigated by absorption titration, competitive binding fluorescence spectroscopy and viscosity measurements. The order of intercalative ability of the coordinated ligands is dppz > phen > phendione > bpy in this series of complexes. 相似文献
999.
Ellis D Lopez ME McIntosh R Rosair GM Welch AJ Quenardelle R 《Chemical communications (Cambridge, England)》2005,(10):1348-1350
Reduction of 1,12-closo-C2B10H12 or its C,C-dimethyl analogue with sodium in liquid ammonia followed by metallation with {CpCo}2+, {(arene)Ru}2+ or {(dppe)Ni}2+ fragments affords the first examples of 4,1,10-MC2B10 species; thermolysis of these yields the appropriate 4,1,12-MC2B10 isomers, unavailable for (arene)Ru metallacarboranes by similar thermolysis of known 4,1,6-MC2B10 compounds. 相似文献
1000.
The water-promoted hydrolysis of a highly twisted amide is studied using density functional theory in conjunction with a continuum dielectric method to introduce bulk solvent effects. The aim of these studies is to reveal how the twisting of the C-N bond affects the neutral hydrolysis of amides. To do so, both concerted and stepwise mechanisms are studied and the results compared to the ones from the hydrolysis of an undistorted amide used as reference. In addition, an extra explicit water molecule that assists in the required proton-transfer processes is taken into account. Our results predict important rate accelerations of the neutral hydrolysis of amides when the C-N bond is highly twisted, the corresponding barrier relaxation depending on the specific reaction pathway and transition state involved. Moreover, our calculations strongly suggest a change in reaction mechanism with degree of amide bond twist, and clearly point to a concerted mechanism at neutral pH for the hydrolysis of highly twisted amides. In addition, the twisting of the amide bond also provokes a higher dependence on an auxiliary water molecule for the concerted mechanism, due to the orthogonality of the lone pair of the nitrogen and the carbonyl pi orbital. There is a direct implication of these findings for biological catalytic mechanism of peptide cleavage reactions that undergoes ground-state destabilization of the peptide. 相似文献