Search results for "NUMB"
showing 10 items of 3956 documents
A theoretical plate model accounting for slow kinetics in chromatographic elution.
2011
The chromatographic elution has been studied from different perspectives. However, in spite of the simplicity and evident deficiencies of the plate model proposed by Martin and Synge, it has served as a basis for the characterization of columns up-to-date. This approach envisions the chromatographic column as an arbitrary number of theoretical plates, each of them consisting of identical repeating portions of mobile phase and stationary phase. Solutes partition between both phases, reaching the equilibrium. Mobile phase transference between the theoretical plates is assumed to be infinitesimally stepwise (or continuous), giving rise to the mixing of the solutions in adjacent plates. This yi…
Extraktionschromatographische trennung der freien uroporphyrinisomere i und iii und deren simultane quantitative bestimmung
1968
Abstract Separation and simultaneous quantitative determination of the free uroporphyrin isomers I and III by means of extraction chromatography Separation and quantitative determination of the uroporphyrin isomers I and III in the acid from can be performed simultaneously in the partition system tri-n-butylphosphate/I N hydrochloric acid using columns with a large number of theoretical plates (N) = 300-450). The eluent is passed through a flow cuvette and the transmission is recorded continuously. The transmission peaks of the isomers are digitized and transformed into extinction values. By integrating the extinction peaks, the amount of the uroporphyrins can be evaluated from the correspo…
Extraktionschromatographische trennung der freien porphyrine auf tri-n-butylphosphat-s?ulen im pH-gradienten
1969
Abstract The method described allows the separation of the free porphyrins on a tri-n-butyl phosphate (TBP) column by elution with a pH gradient. The prophyrins are eluted from the column at discrete pH values (xD) according to the number of carboxyl groups in the side chains. Separation of isomers could not be observed under the conditions used. The xD values indicate the centre of the pH-interval, in which the dissociation of the carboxyl groups occurs. This finding could be confirmed by spectro-photometric measurements. By combining the method proposed with the method of separation by extraction chromatography in the TBP/IN HCl partition system and the thin-layer technique in the 2,6-lut…
Densities, Viscosities, and Refractive Indices of Some Binary Liquid Systems of Methanol + Isomers of Hexanol at 298.15 K
1996
Viscosities, densities, and refractive indices of eight binary liquid systems containing ethanol + some isomers of hexanol have been determined at 298.15 K. The excess property values were fitted to the Redlich-Kister equation to estimate the binary coefficients and the standard deviations.
New insights on the thermal analysis of low moisture composite foods.
2014
Abstract Low moisture baked products were investigated with a view to characterising the effect of both formulation and humidity on their physical stability. At the end of the baking process, the samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with differential scanning calorimetry and their glass transitions were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat flow. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a pl…
Separation of U(VI) and Th(IV) from Some Rare Earths by Thin Layer Chromatography with Di‐(2‐Ethylhexyl)‐Dithiophosphoric Acid on Silica Gel
2005
Abstract Separation of U(VI) and Th(IV) from some rare earths by TLC has been studied using silica gel H and silica gel H impregnated with ammonium nitrate as the stationary phase. The solvent mixture ethyl‐methyl‐ketone–tetrahydrofuran (6∶3, v/v) containing di-(2‐ethylhexyl)-dithiophosphoric acid was used as the mobile phase. When silica gel H impregnated with 2.5 M NH4NO3 was used as stationary phase, the resolution was much improved and the separation of rare earths from each other was also achieved. The tetrad‐effect was observed in variation of R*m versus the atomic number of rare earths.
Variability of isozyme pattern, chromosome number, and latex colour and components in the closely related Papaver duhium L. and P. lecoqii Lamotte in…
1995
Summary The variability of nine different isozyme systems, chromosome number, colour of fresh and dried latex and presence or absence of meconic acid was investigated in altogether 45 populations of Papaver dubium and P. lecoqii mainly from C Europe. It was found that P. dubium is hexaploid with 2n = 42 chromosomes, has brown dried latex, and contains meconic acid. P. lecoqii is tetraploid with 2n = 28 chromosomes, has red dried latex, and lacks meconic acid. The two taxa can also be distinguished by differences in three of the nine isozymes analysed, and are almost completely monomorphic for their respective isozyme pattern. It is concluded that the two taxa, which cannot be reliably disti…
Is <i>Limonium cavanillesii</i> Erben (Plumbaginaceae) really an extant species?
1999
A new triploid apomictic species (Limonium perplexum) is described from a single coastal locality of E Spain. The new species has been previously confused with L cavanillesii Erben, which is only known from few herbarium specimens and it is believed to be extinct. Overall morphology, chromosome number, and the pollen/stigma combination suggest that L perplexum belongs to the L. duriusculum complex. Based on morphological grounds it is suggested that L. cavanillesii Erben could have been originated through a crossing between L perplexum and L dufourii .
<i>Limonium marisolii</i> L. Llorens (Plumbaginaceae) revisited
1998
A new triploid agamic species, L. leonardi-llorensii , is described from coastal populations of South-West Mallorca. The new species is closely related, on morphological grounds, to the endemic L. marisolii L. Llorens, from which it could be distinguished by several morphological characters (leaves without papillae, longer calyx, more flowers per spikelet) and by a different chromosome number ( 2n = 26, L. leonardi-llorensii ; 2n = 27, L. marisolii ). The relationships between both species are discussed, and it is suggested that both taxa might share some common evolutionary history despite their divergent chromosome number. The origin of L. marisolii from L. leonardi-llorensii through chro…
The taxonomic status of <i>Scilla beirana</i> Samp. (<i>Hyacinthaceae</i>)
1998
ALMEIDA DA SILVA, R.M., F.B. CALDAS & J.A. ROSSELLO (1998). The taxonomic status of Scilla beirana Samp. (Hyacinthaceae). Anales Jard. Bot. Madrid 56(2): 253-260. Populations of Scilla beirana Samp. were sampled in NW Portugal and compared with its relatives S. ramburei Boiss, and S. peruviana L. Leaf and scape anatomy, morphology, chromosome number and idiogram were identical in S. beirana and S. ramburei, but differed from S. peruviana. Diagnostic characters previously used to discriminate S. beirana (width of leaves and flower number) showed continuous, but not clinal, variation, and failed to provide a clear-cut basis for identification and no other morphological attributes were found t…