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71.
Information content of data and variables and types of weighting in least-squares regression methods
Algorithms are given for evaluating the relative amount of useful information related to a particular parameter which is carried by individual data points and intervals of the variables. The algorithms provide an efficient means of using the information contained in a set of data. Applications to the optimization of weighting in regression methods are described. Several informational and combined informational-statistical types of weighting are studied as a means of improving the accuracy and precision of the parameters obtained by non-linear regression. 相似文献
72.
García-Raso A Fiol JJ Tasada A Albertí FM Molins E Basallote MG Máñez MA Fernández-Trujillo MJ Sánchez D 《Dalton transactions (Cambridge, England : 2003)》2005,(23):3763-3772
Alkylidene-bis(2-aminopyrimidines) (pyr2Cx, x = 2-5) are useful ligands to interact with Ag(I) yielding discrete metallocycles. Crystal structures of the [(pyr2C2)Ag(NO3)]2 and [(H-pyr2C4)Ag(NO3)2]2 have been isolated where each macrocyclic moiety interacts with their surroundings through weak interactions, yielding 3D discrete structures, On the other hand, the solution study shows that the equilibrium constants for the formation of Ag(pyr2Cx)+ complexes are higher than the literature values for Ag(I) complexes with single pyrimidines, although the differences could be explained by invoking the solid-state structures of the Ag(I)-pyr2Cx complexes. 相似文献
73.
Simple and rapid determination of the drug naproxen in pharmaceutical preparations by heavy atom-induced room temperature phosphorescence 总被引:1,自引:0,他引:1
Segura Carretero A Cruces-Blanco C Ramírez García MI Cañabate Díaz B Fernández Gutiérrez A 《Talanta》1999,50(2):401-407
A simple, selective and sensitive heavy atom-induced room temperature phosphorimetric method (HAI-RTP) is described for the determination of naproxen (NAP) in pharmaceutical preparations. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in presence of a heavy atom salt and sodium sulfite as an oxygen scavenger to minimize RTP quenching. These variables selection constitute the basis of a HAI-RTP method for the determination of naproxen (detection limit 17.6 ng ml(-1); 1.71% relative standard deviation at 250 ng ml(-1)). The method has been applied satisfactorily to the analysis of pharmaceutical preparations. 相似文献
74.
Huenerbein A Sipoli Marques MA Pereira Ados S de Aquino Neto FR 《Journal of chromatography. A》2003,985(1-2):375-386
The Medical Commission of the International Olympic Committee forbids the use of anabolic androgenic steroids and beta2-agonists to improve athletic performance. In this work we have selected examples of anabolic androgenic compounds and their metabolites to evaluate the GC-MS analysis of some trimethylsilyl derivatives. The aim is to set the best GC conditions to improve the detection within the whole range of analyte elution temperatures. The initial column temperature was changed to 105 or 140 degrees C followed by 40 degrees C min(-1) to 200 degrees C and then 15 degrees C min(-1) to 300 degrees C. Using 140 degrees C as the initial oven temperature it was possible to obtain narrower initial analyte distributions for the compounds that elutes at the beginning of the chromatogram as clenbuterol, mabuterol, epimethylenediol and norandrosterone, without loss of derivatized metabolites signal. Later. eluting analytes, such as the stanozolol metabolites, furazabol and oxandrolone were not affected. Temperatures below 140 degrees C. resulted in partial derivatization for some analytes mainly stanozolol related structures. Therefore evaluation of derivatization conditions as occurring in three steps, the vial, vaporization chamber and capillary column, was thoroughly assessed. The new program temperature improves the signal-to-noise ratio for some compounds and shows adequate resolution for endogenous compounds. Some of the difficult key separations necessary for doping control enforcement were also obtained with the proposed method. 相似文献
75.
Fernández LE Verón MG Varetti EL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(1-2):405-411
Force fields and vibrational wavenumbers were calculated for the molecules SO2X2 (X=F, Cl, Br) using DFT techniques. The previously available experimental data and assignments for SO2F2 and SO2Cl2 were compared with the theoretical results and revised, and new low temperature infrared and Raman data were obtained for SO2Cl2. These data were subsequently used in the definition of scaled quantum mechanics force fields for such molecules. Adjusted wavenumbers were also predicted for the still unknown SO2Br2. A comparison is made with results published for the VO2X2- anions. 相似文献
76.
Synthesis of 1-(4-substituted)benzyl-6-hydroxyisoquinolines with potential activity on NA+,K+-atpase
Alberto Cerri Paola Mauri Marina Mauro Piero Melloni 《Journal of heterocyclic chemistry》1993,30(6):1581-1591
The synthesis of 1-(4-substituted)benzyl-6-hydroxyisoquinolines, to be evaluated in the displacement of the specific 3H-ouabain binding to Na+,K+-ATPase, is described. The key step involved a cyclization to the isoquinoline ring under Pictet-Gams conditions which was best performed with the 6-hydroxy group protected as the benzyl ether. When an unsaturated ester group was present in position 4 of the 1-benzyl group, this was best introduced before the cyclization step, since the IIeck reaction on 1-(4-bromobenzyl)-6-hydroxyisoquinoline ( 8 ) with acrylic acid derivatives was not successful in all cases. 相似文献
77.
Journal of Algebraic Combinatorics - Let $$\Gamma $$ denote a finite, simple and connected graph. Fix a vertex x of $$\Gamma $$ and let $$T=T(x)$$ denote the Terwilliger algebra of $$\Gamma $$ with... 相似文献
78.
Aringhieri Roberto Bigharaz Sara Duma Davide Guastalla Alberto 《Central European Journal of Operations Research》2022,30(1):189-211
Central European Journal of Operations Research - Disaster management generally includes the post-disaster stage, which consists of the actions taken in response to the disaster damages. These... 相似文献
79.
Hereditarily finite sets and hypersets are characterized both as algorithmic data structures and by means of a first-order axiomatization which, despite being rather weak, suffices to make the following two problems decidable:
- (1) Establishing whether a conjunction r of formulae of the form: ? y1 ?? ym((y1?W1& ?&ym ?Wm) ←q), with q quantifier-free and involving only the relators =, ? and propositional connectives, and each yi distinct from all wj's, is satisfiable.
- (2) Establishing whether a formula of the form ? y q, q quantifier-free, is satisfiable.
80.
A comparative electrochemical study of 2,4-dinitrophenol (DNP), albumin and DNP-albumin has been carried out at a hanging mercury drop electrode, in order to use DNP as a universal label in immunoelectrical assays. Several electrochemical techniques have been used. Differential pulse voltammetry has proved to be the most suitable. Wide dynamic linear ranges (more than three orders of magnitude for DNP-albumin) and low detection limits have been achieved (5 x 10(-10)M, 2 x 10(-10)M, 3 x 10(-12)M for DNP, albumin and DNP-albumin, respectively). Good reproducibility has been obtained in all cases (R.S.D. < 2.2%). 相似文献