共查询到20条相似文献,搜索用时 187 毫秒
1.
This paper discusses some of the contentious issues raised by van der Veen (Accred Qual Assur 8:334, 2003[1]), and Van Eenoo and Delbeke (Accred Qual Assur 8:477, 2003 [2]) concerned with the evaluation of the uncertainty of measurement and compliance decisions based on regulatory limits. Also, the criticisms of accreditation by van der Veen are considered and some general remarks about the strengths and limitations of accreditation provided. It is concluded that a position between those adopted by van der Veen and by Van Eenoo and Delbeke would be more appropriate. 相似文献
2.
Walter Bich 《Accreditation and quality assurance》2009,14(7):389-392
A recent paper by Nam et al. (Accred Qual Assur 14:43–47, 2009) considers the issue of repeated measurements of a same measurand.
The paper is a follow-up of two previous papers (Choi et al. in Accred Qual Assur 8:13–15, 2003, 8:205–207, 2003) on the
same topic. The first two papers show a well-known fact, i.e., that systematic effects are not reduced by repeating measurements,
and give formulae for the uncertainty of the estimate of the average from repeated measurements in the case that the differences
between individual results are not (Choi et al. in Accred Qual Assur 8:13–15, 2003) or are (Choi et al. in Accred Qual Assur
8:205–207, 2003) statistically significant, respectively. The last paper addresses a more interesting issue, that is, a difference
in the estimate average for non-linear models depending on how raw data is processed in the model. In the present paper, I
re-discuss the whole issue of multiple measurements, trying to clarify the various aspects of the topic.
Papers Published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board, and the Publisher. 相似文献
3.
R. Willink 《Accreditation and quality assurance》2010,15(9):521-527
This article discusses the measurement of the sum of small positive quantities each estimated in separate analyses. It extends
criticism recently given of ‘objective Bayesian’ methodology (Accred Qual Assur 15:181–188, 2010) and identifies two troublesome
effects: the inherent bias in an analysis for a single quantity is compounded when the measurand is the sum of such quantities,
and the precaution of overestimating measurement variability can actually make the resulting interval of measurement uncertainty
less reliable! Unacceptable results are obtained. A cause of this behavior is identified, and a distinction between ‘objective’
and ‘subjective’ Bayesian statistics is discussed. 相似文献
4.
A discussion of proficiency testing (PT) topics started by Heydorn (Accred Qual Assur 15:643–645, 2010) is continued in the present paper. The role of PT in the accreditation of testing/analytical laboratories, the use of consensus
values (average or weighted average, median, observed standard deviation, etc.) and a metrological background of PT schemes
are discussed. It is shown that metrological traceability, comparability, and compatibility, as well as commutability of a
reference material, are the key issues of any PT scheme that applies certified reference material as test items. Metrological
compatibility of PT results in such schemes is a property demonstrating the closeness of the PT results to the certified value
in comparison with the measurement uncertainty of their difference. The metrological background is especially important for
the selection and use of PT schemes for a limited number of participants (fewer than 30) as detailed in IUPAC/CITAC Guide
on the topic published in 2010 in Pure Appl Chem 82(5):1099–1135. 相似文献
5.
Robin Willink 《Accreditation and quality assurance》2009,14(12):693-700
A recent paper of Meinrath (Accred Qual Assur 13:179–192, 2008) addresses matters of statistical analysis when the data are
thought to have been drawn from a normal distribution with unknown mean and variance. In this comment we clarify, correct
and enlarge upon points made there. 相似文献
6.
Robin Willink 《Accreditation and quality assurance》2010,15(3):181-188
This article considers the problem of uncertainty evaluation when there are repeated measurements of a small quantity known
to be non-negative. A solution to this problem has recently been put forward by the Analytical Methods Committee of the Royal
Society of Chemistry (Accred Qual Assur 13:29–32). The Bayesian statistical basis of this solution is explained and discussed.
It is shown that the performance of this procedure can be poor in an important subset of measurement situations. 相似文献
7.
Ilya Kuselman 《Accreditation and quality assurance》2006,10(12):659-663
A nonparametric sign test is implemented for assessment of comparability of proficiency testing (PT) results when their distribution differs from the normal or other known distribution. It allows testing the null hypothesis about insignificance of the bias of median of results obtained in PT from the traceable certified value of the reference material used in PT as test items, i.e., the hypothesis stating that comparability of the PT results is successful. Probability of type I error of rejecting the null hypothesis when it is true, and probability of type II error of it not rejecting when it is false (the alternative hypothesis about unsuccessful comparability is true) are considered. The test can be helpful for PT providers and laboratory accreditation bodies in analysis of PT results when the comparability criterion developed for a normal results distribution (Accred. Qual. Assur. 10:466–470) is not applicable. 相似文献
8.
We give the sharp lower bound on the number of minimal reactions when no “parallel” species (isomers or multiples) are allowed
and all the species are built up from at most four kinds of atoms in Theorem 16. This continues the investigations in Kumar and Pethő (Intern Chem Eng 25:767–769, 1985) through Szalkai and Laflamme (Electr J Comb 5(1), 1998) which results we briefly summarize in the first Section. 相似文献
9.
Julian Weghuber Stefan Sunzenauer Birgit Plochberger Mario Brameshuber Thomas Haselgrübler Gerhard J. Schütz 《Analytical and bioanalytical chemistry》2010,397(8):3339-3347
We have recently devised a method to quantify interactions between a membrane protein (“bait”) and a fluorophore-labeled protein
(“prey”) directly in the live-cell plasma membrane (Schwarzenbacher et al. Nature Methods 5:1053–1060 2008). The idea is to seed cells on surfaces containing micro-patterned antibodies against the exoplasmic domain of the bait,
and monitor the co-patterning of the fluorescent prey via fluorescence microscopy. Here, we characterized the time course
of bait and prey micropattern formation upon seeding the cells onto the micro-biochip. Patterns were formed immediately after
contact of the cells with the surface. Cells were able to migrate over the chip surface without affecting the micropattern
contrast, which remained constant over hours. On single cells, bait contrast may be subject to fluctuations, indicating that
the bait can be released from and recaptured on the micropatterns. We conclude that interaction studies can be performed at
any time-point ranging from 5 min to several hours post seeding. Monitoring interactions with time opens up the possibility
for new assays, which are briefly sketched in the discussion section. 相似文献
10.
Four approaches for estimation of reference values and their respective uncertainties of characterisation were compared using
data from the recently finalised certified reference materials ERM-EC680k and ERM-EC681k, elements in plastics. Reference
values and uncertainties of characterisation were estimated as mean of laboratory means and their respective standard deviations,
using equal weights and the weighting procedure of Mandel–Paule. In addition, two approaches taking into consideration uncertainty
information reported by the participants, namely the consistency check and simulation procedure proposed by Cox for CCQM Key
comparisons and an approach suggested by Pauwels et al. (Accred Qual Assur 3:180–184, 2000) were used. No difference between
the equally-weighted and Mandel–Paule consensus means was observed and the reference value from the Cox approach was in all
cases within ±2 u
char of each consensus mean. Uncertainties varied between the three approaches. Uncertainties derived from equally-weighted mean
of means approach are on average 14% above uncertainties using the Mandel–Paule consensus mean, 36% above the uncertainties
estimated by Pauwels et al., and 54% above the uncertainties from the Cox approach. Robustness of the uncertainty estimation
against incorrect estimation of uncertainties was assessed. Assumption of a 50% uncertainty of the individual uncertainties
resulted in an uncertainty of 30% of the uncertainty of characterisation. Differences between the four approaches are negligible
for this dataset when combined with the uncertainty contribution from heterogeneity and stability as prescribed in ISO Guide
35.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Oana Moldovan Pedro Lameiras Eric Henon Flavia Popa Agathe Martinez Dominique Harakat Carmen Sacalis Yvan Ramondenc Mircea Darabantu 《Central European Journal of Chemistry》2012,10(4):1119-1136
The highly chemoselective preparation of new elaborated N-unsymmetrically substituted chlorodiamino-s-triazines and melamines, seen as building-blocks for iterative synthesis, is reported. It consisted of amination of cyanuric
chloride with commercial C-2-substituted 2-aminopropane-1,3-diols (“serinols”), playing the role as “open-chain” unit and enantiopure (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diols (“p-nitrophenylserinols”) based amino-1,3-dioxanes (“closed-chain” unit). Issued from the restricted rotation about C(s-triazine)-N(exocyclic) partial double bonds, seen as axes of (pro)diastereomerism,
a global four-component rotational equilibrium involving the title compounds is discussed based on DFT computation and (VT)
NMR data. Depending on π-deficiency of the s-triazine core, an (un)synchronised deblocking of the generated rotational diastereomers was observed. They are discussed
as influence of intra-vs. intermolecular NH...OH (dynamic) interactions occurring in the “open-chain” unit and the anancomeric, axial vs. equatorial, amino-anchorage of the “closed-chain” unit.
相似文献
12.
Diastereoisomeric [(1R,5S)-5-“[(1R)-1-phenylethyl]aminocarbonyl”cyclopent-2-en-1-yl]methyl acetate and [(1S,5R)-5-“[(1R)-1-phenylethyl]aminocarbonyl”cyclopent-2-en-1-yl]methyl acetate reacted with m-chloroperoxybenzoic acid to give the corresponding stereoisomeric α- and β-epoxy derivatives, which were identified on the
basis of their spectral parameters. 相似文献
13.
V. A. Nikanorov O. L. Tok S. G. Novikov S. V. Sergeev E. V. Vorontsov I. D. Gridnev D. V. Zverev A. T. Lebedev 《Russian Chemical Bulletin》1997,46(2):350-354
Three approaches to the synthesis ofN-substituted imino-, hydrazono-, and azino-2,5-cyclohexadienylidene systems based on reactions of 4-methyl-4-trichloromethylcyclohexa-2,5-dienone
with aminophenols and hydrazones and condensation of hydrazones ofpara-semiquinoid ketones with carbonyl compounds, including that of the ferrocene series, were realized. The latter reaction,
when applied to 3,6-dibromophenanthrene-9, 10-quinone, was accompanied by quantitative aromatizational molecular rearrangement
with the elimination of the CCl3 group. Using Rh1 complexes as an example, it was shown that the heteroorganic ligands obtained can be used for the synthesis of mixed-ligand
metallocomplexes with triple coordination of the metal atom including simultaneous metal-ligand interactions of the n-, π-,
and σ-types.
The principle of metal-ligand “cascade” appeared as a result of the generalization of two new phenomena of organometallic
sereodynamics, which we have found recently2,3 and have called oxidative and reductive redox-rotation. In the “cascade”, type1 (“metal-ligand-metal”) or type2 (“ligand-metal-ligand”) metallocomplexes, one or several coordinated metal ligand”) metallocomplexes, one or several coordinated
metal atoms capable of concertedly and reversibly changing their valence in the course of intramolecular conformational transformation
are in positions of mutual conjugation.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 363–367, February, 1997. 相似文献
14.
Matthew Hudelson 《Journal of mathematical chemistry》2010,47(1):219-228
We expand on the work of Hosoya to describe a generalization of continued fractions called “tree expressions.” Each rooted
tree will be shown to correspond to a unique tree expression which can be evaluated as a rational number (not necessarily
in lowest terms) whose numerator is equal to the Hosoya index of the entire tree and whose denominator is equal to the tree
with the root deleted. In the development, we use Z(G) to define a natural candidate ζ(G, v) for a “vertex topological index” which is a value applied to each vertex of a graph, rather than a value assigned to the
graph overall. Finally, we generalize the notion of tree expression to “labeled tree expressions” that correspond to labeled
trees and show that such expressions can be evaluated as quotients of determinants of matrices that resemble adjacency matrices. 相似文献
15.
Chun-lan Yuan 《Kinetics and Catalysis》2011,52(5):697-701
A closed oscillation system comprised of alanine, KBrO3, H2SO4 and acetone catalyzed by tetraazamacrocyclic nickel(II) complex is introduced, and quantitatively characterized with kinetic
parameters, namely the rate constant (k
in, k
p), the apparent activation energy (E
in, E
p) and pre-exponential constant (A
in, A
p) and thermodynamic functions (ΔH
in, ΔG
in, ΔS
in and ΔH
p, ΔG
p, ΔS
p), where indexes “in” and “p” mean “induction period” and “oscillation period,” respectively. The results indicate that tetraazamacrocyclic
nickel(II) complex can catalyze alanine oscillating reaction and the reaction corresponds exactly to the feature of irreversible
thermodynamics as the entropy of system is negative. 相似文献
16.
Pirjo Sainio Irma Mäkinen Jaap-Willem Hutter Theo den Ouden Mikael Krysell 《Accreditation and quality assurance》2006,11(3):116-121
The international joint project HYCREF (Contract No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogeneous and stable reference materials of water, soil, and waste contaminated with mineral oil hydrocarbons and to certify the mineral oil content by gas chromatographic methods. The results of a feasibility study for the preparation of three soil reference materials are discussed in this paper, and for the preparation of three waste reference materials in the second part (Koch et al., Accred Qual Assur submitted for publication). The soil materials were selected to represent different soil types and contamination levels. The project plan set three requirements for these reference materials: uncertainty in the mineral oil content resulting from the certification exercise <5%, a sample inhomogeneity of <3% and a minimum long-term stability of 5 years. For the most part, these requirements were met within this project. 相似文献
17.
Zusammenfassung Die zur Zeit als Verpackungsmaterial in den Handel kommende Zellulosefolie Kuprophan wurde auf ihre Verwendbarkeit als Dialysenmembran
untersucht. Es ergab sich, da? die „Durchl?ssigkeit“ von Kuprophan etwa doppelt so gro? ist wie die von Cellophan Qual. 300
und etwa achtmal so gro? wie die von Pergamentpapier zur Dialyse C 155∶100, da? also bei Anwendung der Kuprophanmembran die
Dialyse in der H?lfte der bei Verwendung von Cellophan Qual. 300 und im achten Teil der bei Gebrauch von Pergamentpapier als
Membran erforderlichen Zeit beendet ist. Die mechanische Festigkeit von Kuprophan ist gut, trotz der nur geringen St?rke von
10Μ. Kuprophan ist daher, neben Cellophan Qual. 300, als hervorragend geeignetes Membran-material anzusprechen. 相似文献
18.
19.
Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the
fusion enthalpy and temperature determination of the biuret (NH2CO)2NH (synthesis by-product of the urea fertilizer (NH2)2CO). Recommended values are Δm
H = (26.1 ± 0.5) kJ mol−1, T
m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems
to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature
of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested. 相似文献
20.
Hong-Liang Xu Shi-Ling Sun Shabbir Muhammad Zhong-Min Su 《Theoretical chemistry accounts》2011,128(2):241-248
Significant alkali-metal-doped effects on the structure and the first hyperpolarizability (β
0) of effective multi-nitrogen complexant tris[(2-imidazolyl)methyl]amine (TIMA) are investigated. Three imidazoles of TIMA
like three blades of propeller connect with methyls by the C–C single bonds. Because of the three C–C single-bond cooperative
rotations, the TIMA behaves with great flexibility, and it is a high-performance multi-nitrogen complexant for the alkali
metal doping. Thus, the new complexes Am-TIMA (Am = Li, Na, and K) with electride characteristic have diffuse excess electron than the reported electride-type system due to
the strong interaction between the complexant TIMA and alkali metal. For the first hyperpolarizability, three engaging electrides
Am-TIMA with the diffuse excess electrons exhibit considerably large β
0 values using the MP2 (full) method and the β
0 values of new electrides are greatly larger (3,464–29,705 times) than that (338 au) of TIMA. Surprisingly, the K-TIMA sets
a new record β
0 value to be 1.00 × 107 au which far exceeds than that (3,694–76,978 au) of the reported electride-type system Li@calix[4]pyrrole (J Am Chem Soc
127:10977–10981, 2005) and Lin−H−(CF2−CH2)3−H (n = 1, 2) (J Am Chem Soc 129:2967–2970, 2007) and 31,123 au of the organometallic system (J Am Chem Soc 121:4047–4053, 1999) Ru(trans-4,4′-diethylaminostyryl-2,2′-bipyridine)32+, as well as 1.23 × 106 au of the large donor-CNT systems (Nano Lett 8:2814–2818, 2008). Clearly, the alkali-metal-doped effect on the first hyperpolarizability is very dramatic for the high-performance multi-nitrogen
complexant TIMA. Considering simple possibility from molecule to material, the β
0 values of optimized Li-TIMA-dimer and Li-TIMA-tetramer are investigated by BHandHLYP method. Interestingly, results show
that the order of β
0 value is Li-TIMA-monomer < Li-TIMA-dimer < Li-TIMA-tetramer. So the new three-propeller-blade-shaped electrides can be considered
as candidates for high-performance nonlinear optical materials. 相似文献