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61.
Debeljak Z Srecnik G Madić T Petrović M Knezević N Medić-Sarić M 《Journal of chromatography. A》2005,1062(1):79-86
Instead of usual rationale for chromatographic fingerprint based sample identification which relies upon visual inspection or principal component analysis of raw or aligned chromatograms novel nonparametric statistical measure of fingerprint set homogeneity is proposed. Randomization test is applied for significance analysis of fingerprint set homogeneity while average maximum crosscorrelation is used as a merit function. Chromatogram sets generated by random selection from standard and unknown sample chromatogram collections are compared with respect to merit function values with set of chromatograms that represents standard and/or unknown sample. In that instance fingerprint homogeneity significance is represented by the fraction of random chromatogram sets that have higher merit values than the standard and/or unknown sample sets. A set of peptide maps corresponding to different haemoglobin variants has been selected for evaluation of proposed test. This approach is compared to chromatogram alignment based on correlation optimized warping coupled with principal component or cluster analysis. Proposed method is simple i.e. straightforward sample identification procedure which reliability has been evaluated here. Impact of this approach on peptide mapping validation and system suitability analysis is discussed. 相似文献
62.
Precise conductance measurements have been performed for lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, sodium perchlorate, and sodium tetraphenylborate in 2-methoxyethanol–water mixtures at four different mole fractions, i.e., 0.056, 0.136, 0.262, and 0.486 of 2-methoxyethanol (69.73 D 26.55) at 25°C in the concentration range 0.0004–0.0642 mol-dm–3. The limiting molar conductivity °, the association constant K
A, and the association distance R for the solvent mixtures have been evaluated from the conductance concentration data using the 1978 Fuoss conductance equation. The single-ion conductances have been estimated using the reference electrolyte tetrabutylam-monium tetraphynylborate(Bu4NBPh4). The analysis of the data indicates that for most salts ion association is appreciable in the solvent mixtures with a mole fraction of the cosolvent of 0.262 or higher. The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvent media. 相似文献
63.
Some new tetradentate ligands with a NNOS coordination sphere were prepared and their corresponding nickel(II) complexes were synthesized and characterized by elemental analysis, IR, 1H NMR, UV–Vis and mass spectrophotometry. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at a constant ionic strength of 0.1 M (NaClO4) at 25 °C in DMF solvent. The trend of the complex formation for nickel is as follows: 相似文献
64.
Elshani S Chun S Amiri-Eliasi B Bartsch RA 《Chemical communications (Cambridge, England)》2005,(2):279-281
New lipophilic acyclic polyethers with two N-(X)sulfonyl carbamoyl groups of "tunable" acidity exhibit remarkable selectivity for Ba2+ over other alkaline earth metal ions in competitive solvent extraction and transport across polymer inclusion membranes. 相似文献
65.
Bijan?SahaEmail author G.?N.?Shikin 《International Journal of Theoretical Physics》2005,44(9):1459-1494
We consider a system of minimally coupled nonlinear spinor and scalar fields within the scope of a plane-symmetric gravitational
field. The gravitational field plays crucial role in the formation of soliton-like solutions, i.e., solutions with limited
total energy, spin, and charge. The change of the sign of the scalar field energy density of the system in question realizes
physically if and only if the scalar charge does not exceed some critical value. In case of spinor field no such restriction
on its parameter occurs. The choice of spinor field nonlinearity leads to the elimination of scalar field contribution to
the metric functions, but leaves its contribution to the total energy unaltered. The spinor field is more sensitive to the
gravitational field than the scalar field. 相似文献
66.
Bijan Etemadi Abdol Abadi David S. Moss Rex A. Palmer 《Journal of chemical crystallography》1984,14(3):269-281
The crystal structure of the versatile folk medicine berberine hydrogen sulfate, (C20H18NO4)+HSO
4
–
, has been determined by the heavy-atom method and refined by blocked full-matrix least-squares refinement. The crystals are triclinic, space groupF¯1,a=20.370(5),b=7.435(2),c=27.427(6) Å,=97.700(9),=116.222(9),=85.456.(8)°,Z=8,D
x
=1.556 g cm–3,D
m
=1.549(5) g cm–3. The structure refined toR=0.070 for 1659 observed reflections withI(hkl)2.5[I(hkl)]. The ring system of the berberine molecule is approximately planar, with both –OCH3 groups twisted slightly out of the plane. Heterocyclic ringB has a half-chair conformation with a pseudo-two-fold axis bisecting the bonds C(9)-C(10) and C(7)-C(8), diagonal to the isoquinoline groupAB. The five-membered ringE has an envelope conformation, the apical atom C(1) being out of plane. 相似文献
67.
LetG be a finite group and #Cent(G) denote the number of centralizers of its elements.G is calledn-centralizer if #Cent(G)=n, and primitiven-centralizer if #Cent(G)=#Cent(G/Z(G))=n. In this paper we investigate the structure of finite groups with at most 21 element centralizers. We prove that such a group is solvable and ifG is a finite group such thatG/Z(G)?A5, then #Cent(G)=22 or 32. Moroever, we prove that A5 is the only finite simple group with 22 centralizers. Therefore we obtain a characterization of A5 in terms of the number of centralizers 相似文献
68.
Bijan Das 《Journal of solution chemistry》2004,33(1):33-45
The ion interaction parameters (Pitzer parameters), (0), (1), and C
for 52 single 1-1 electrolytes in aqueous solutions have been obtained from experimental data in the literature on the thermodynamic properties at 25°C using Pitzer's equations. Out of these 52 electrolytes investigated, the ion interaction parameters for nine of them have been reported earlier, but those analyses were limited to only the low concentration region. The present evaluations, however, include the higher concentration data for these systems. The calculated activity coefficients of lithium methanesulfonate, sodium methanesulfonate, potassium methanesulfonate, p-toluenesulfonic acid, 2,5-dimethylbenzenesulfonic acid, sodium formate, sodium acetate, sodium propionate, and ammonium bromide from this analysis and those from earlier evaluations are compared to the available experimental data. The comparisons show better agreement with experimental data when we use the present set of parameters evaluated with data extending to higher concentrations than those reported earlier. In general, the parameters obtained in this study reproduce quite satisfactorily the experimental thermodynamic properties of the electrolytes studied over the entire concentration range. The implications of these parameters are also discussed in terms of interionic forces. 相似文献
69.
Wavelength tuning characteristics of a fabry-perot semiconductor laser with an external short cavity
Wavelength tuning characteristics of a Fabry-Perot semiconductor laser with an external short cavity are analyzed, in which
the oscillation wavelength can be changed by slightly altering the external cavity length. Analysis is based on rate equations
for an optical power and carrier density. It is shown that the wavelength tuning range is dominated by a change of carrier
density through the effect of carrier-induced refractive index change in the active layer of a laser diode. This depends on
effective coupling coefficients of the optical field iteratively reflected back to the laser diode by the external mirror,
and on reflection coefficients of an anti-reflection coated laser facet and the external mirror which compose the external
cavity. The effective coupling coefficient is also derived using the waveguide theory and Kirchhoff ’s theory. Finally, an
unstable condition which may limit a stable wavelength tuning range is shown by results of a linear stability analysis of
rate equations. 相似文献
70.
In this research the fluid dynamics characteristics of a stellar turbulent jet flow is studied numerically and the results
of three dimensional jet issued from a stellar nozzle are presented. A numerical method based on control volume approach with
collocated grid arrangement is employed. The turbulent stresses are approximated using k–ε and k–ω models with four different inlet conditions. The velocity field is presented and the rate of decay at jet centerline is noted.
Special attention is drawn on the influence of corner angle and number of wings on mixing in stellar cross section jets. Stellar
jets with three; four and five wings and 15–65° corner angles are studied. Also the effect of Reynolds number (based on hydraulic
diameter) as well as the inflow conditions on the evolution of the stellar jet is studied. The Numerical results show that
the jet entrains more with corner angle 65° and five wings number. The jet is close to a converged state for high Reynolds
numbers. Also the influence of the inflow conditions on the jet characteristics is so strong. 相似文献