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111.
L. I. Komarova Ts. M. Frenkel' A. E. Shvorak V. A. Pankratov B. N. Lokshin 《Russian Chemical Bulletin》1996,45(7):1572-1578
The structure of the dimethylbenzylamine (DMBA)—phenylglyc idyl ether (PGE)—phenol complex was studied by IR and1H NMR spectroscopy under various conditions of its formation. The active catalyst in the cyclotrimerization of isocyanates is a complex of composition DMBA : PGE : PhOH = 1 : 1 : 2, in which the oxygen atom of the zwitter-ion PhCH2N+Me2CH2CH(O–)CH2OPh that forms after opening, of the epoxide cycle is bound to two phenol molecules by a very strong hydrogen bonds. In this complex, the oxygen atom of both the zwitter-ion and the phenolate anion can be catalytic centers. Two schemes of the cyclotrimerization of isocyanate in the presence of the aforementioned catalytic system are suggested, depending on whether the catalytic complex has time to form or not.For Part I, see Ref. 1.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1662–1668, July, 1996. 相似文献
112.
113.
Arthur Cohen 《Journal of multivariate analysis》1977,7(3):454-460
Let Ui = (Xi, Yi), i = 1, 2,…, n, be a random sample from a bivariate normal distribution with mean μ = (μx, μy) and covariance matrix . Let Xi, i = n + 1,…, N represent additional independent observations on the X population. Consider the hypothesis testing problem H0 : μ = 0 vs. H1 : μ ≠ 0. We prove that Hotelling's T2 test, which uses (Xi, Yi), i = 1, 2,…, n (and discards Xi, i = n + 1,…, N) is an admissible test. In addition, and from a practical point of view, the proof will enable us to identify the region of the parameter space where the T2-test cannot be beaten. A similar result is also proved for the problem of testing μx ? μy = 0. A Bayes test and other competitors which are similar tests are discussed. 相似文献
114.
Historically, due to the size and nature of the instrumentation, highly skilled laboratory professionals performed clinical
testing in centralized laboratories. Today’s clinicians demand realtime test data at the point of care. This has led to a
new generation of compact, portable instruments permitting ”laboratory” testing to be performed at or near the patient’s bedside
by nonlaboratory workers who are unfamiliar with testing practices. Poorly controlled testing processes leading to poor quality
test results are an insidious problem facing point of care testing today. Manufacturers are addressing this issue through
instrument design. Providers of clinical test results, regardless of location, working with manufacturers and regulators must
create and manage complete test systems that eliminate or minimize sources of error. The National Committee for Clinical Laboratory
Standards (NCCLS) in its EP18 guideline, ”Quality management for unit-use testing,” has developed a quality management system
approach specifically for test devices used for point of care testing (POCT). Simply stated, EP18 utilizes a ”sources of error”
matrix to identify and address potential errors that can impact the test result. The key is the quality systems approach where
all stakeholders – professionals, manufacturers and regulators – collaboratively seek ways to manage errors and ensure quality. We illustrate the use of one quality systems approach, EP18, as a means to advance the quality of test results at point of
care.
Received: 26 June, 2002 Accepted: 17 July 2002
Presented at the European Conference on Quality in the Spotlight in Medical Laboratories, 7–9 October 2001, Antwerp, Belgium
Abbreviations NCCLS National Committee for Clinical Laboratory Standards (formerly) · POCT point of care testing · QC quality control ·
HACCP hazard analysis critical control points · CLIA clinical laboratory improvement amendments (of 1988)
Correspondence to S. S. Ehrmeyer 相似文献
115.
应用量子化学HF/3-21G从头算法得到了20种有机分子的优势构象,利用HF/3-21G和分子图形学技术获得其电子结构参数和几何结构参数,并将这些参数与有机物对蝴蝶幼虫的麻醉活性相关联.结果表明,有机物麻醉活性与分子的范德华体积、分子最低空轨道能和分子偶极矩之间存在良好的多元线性相关性,成功地建立有机物对蝴蝶幼虫麻醉活性的构效关系式. 相似文献
116.
Siu Kay Wong 《Accreditation and quality assurance》2005,10(8):409-414
Proficiency testing (PT) is an essential tool used by laboratory accreditation bodies to assess the competency of laboratories.
Because of limited resources of PT providers or for other reasons, the assigned reference value used in the calculation of
z-score values has usually been derived from some sort of consensus value obtained by central tendency estimators such as the
arithmetic mean or robust mean. However, if the assigned reference value deviates significantly from the ‘true value’ of the
analyte in the test material, laboratories’ performance will be evaluated incorrectly. This paper evaluates the use of consensus
values in proficiency testing programmes using the Monte Carlo simulation technique. The results indicated that the deviation
of the assigned value from the true value could be as large as 40%, depending on the parameters of the proficiency testing
programmes under investigation such as sample homogeneity, number of participant laboratories, concentration level, method
precision and laboratory bias. To study how these parameters affect the degree of discrepancy between the consensus value
and the true value, a fractional factorial design was also applied. The findings indicate that the number of participating
laboratories and the distribution of laboratory bias were the prime two factors affecting the deviation of the consensus value
from the true value. 相似文献
117.
Terry Spencer 《Accreditation and quality assurance》2005,10(6):308-314
This presentation deals with issues of comparability and traceability in food analysis in Australia from several perspectives. This includes the current national (Australian) and increasingly international (Codex) performance-based approach to food analysis. The Australian food regulatory process will be described, particularly those aspects that impact on the analysis of food in a regulatory sense. This section will also describe two areas where specific methods have been mandated in legislation and discuss two case studies where the analytical method has impacted on the elaboration of standards. Other areas to be covered include regulation/requirements relating to supply/availability of reference materials, the use of proficiency testing as a means of ensuring comparability, and, finally, some thoughts on what role BIPM/CCQM may play in the analysis of food.Electronic Supplementary Material Supplementary material is available for this article at
相似文献
Terry SpencerEmail: Phone: +612-6213-6102Fax: +612-6213-6815 |
118.
The robustness testing of a normal-phase liquid chromatographic (LC) method for the determination of R-timolol and other related substances in S-timolol maleate was performed applying a two-level Plackett-Burman design. Two qualitative and five quantitative factors were examined. Two types of responses were considered, qualitative, i.e. chromatographic performance criteria, and quantitative ones. The latter were taken into account to determine if the analytical procedure was robust. The quantitative responses were the contents of R-timolol in two S-timolol maleate samples. Even though some significant factor effects were observed on the qualitative responses, the R-timolol contents were not significantly different from those observed at nominal conditions, which demonstrated the robustness of the procedure.Since the experiments of the Plackett-Burman design can be assimilated to laboratories in an interlaboratory study, uncertainty can be evaluated using the robustness test data. The robustness test was set-up in such a way that the required variances could be estimated. It was shown that the robustness set-up allows estimating the reproducibility uncertainty without performing an interlaboratory study. 相似文献
119.
120.
The new compound CuSb2O3Br crystallize in the monoclinic space group Cc. The unit cell parameters are , , , β=90°, Z=16. The crystal structure is solved from single crystal data, R=0.0490. The compound show a layered structure with slabs from cubic Sb2O3 interspersed in between puckered layers of CuBr. The Sb(III) atoms have tetrahedral [SbO3E] coordination where E is the 5s2 lone pair, these units build up Sb4O4E6 cages. The CuBr layers resemble those in hexagonal CuBr but the Cu(I) ions have actually tetrahedral [CuBr3O] coordination. The Cu-O bonds link the Sb4O6 cages with the CuBr layers. 相似文献