Classification of chromatographic data using multidimensional polynomials

Summary A pattern recognition methodology has been developed for analysis of chromatographic data. The method uses a new class of multidimensional orthogonal polynomials developed by Cohen in conjunction with a supervised learning technique. The method is applicable to any chromatographic data for which classification into two or more categories is desired. The algorithm analyzes both elution times and peak areas. An application is shown for the analysis of organic acids in ascitic fluid obtained from patients with liver disorders. Classification of these patients for presence or absence of bacterial infection shows over ninety percent correct classification.     

Decompositions of metastable [C6H12O]+ ions with the oxygen on the third carbon: Ring-size preferences in [CnH2nO]+˙ ions

The isomerizations preceding the metastable decompositions in the mass spectrometer of a number of [C₆H₁₂O]⁺˙ ions with the oxygen on the third carbon are characterized utilizing deuterium labeling. Hydrogens are transferred in these ions by three-, five- and six-membered ring rearrangements, with propensities determined by features of the individual reactions. Three-membered ring hydrogen transfers between α and β-carbons are preferred to all five-membered ring hydrogen transfers. However, six-membered ring hydrogen transfers take place to the apparent exclusion of three-membered ring hydrogen transfers to enol carbons when the products are of comparable stability. The low-energy [C₆H₁₂O]⁺˙ isomerizations characterized are predictable from the behavior of their lower homologs. It is concluded that the determinants of these reactions are the same as those of other highly reactive organic intermediates.     

Transient flow near a rotating disk

Summary The solution of the time dependent flow due to the impulsive starting of a single infinite disk from rest is obtained numerically for the entire history of the transient. The primary tangential velocity exhibits a single overshoot of its steady value while the growth of the secondary flows is monotonic. The overshoot is seen to be a direct consequence of the lag in the development of the secondary flows. An analytical solution is obtained for a related linearized problem: The angular velocity of an infinite disk, initially rotating with an infinite environment, is perturbed. The oscillatory decays to the steady state, which occur in both unbounded and bounded linearized analyses, are discussed in relation to the overshoot in the impulsively started disk problem.     

Sigmoids as precursors of solar eruptions

Coronal mass ejections (CMEs) appear to originate preferentially in regions of the Sun's corona that are sigmoidal, i.e., have sinuous S or reverse-S shapes. Yohkoh solar X-ray images have been studied before and after a modest number of Earth-directed (halo) CMEs. These images tend to show sigmoidal shapes before the eruptions and arcades, cusps, and transient coronal holes after. Using such structures as proxies, it has been shown that there is a relationship between sigmoidal shape and tendency to erupt. Regions in the Sun's corona appear sigmoidal because their magnetic fields are twisted. Some of this twist may originate deep inside the Sun. However, it is significantly modulated by the Coriolis force and turbulent convection as this flux buoys up through the Sun's convection zone. As the result of these phenomena, and perhaps subsequent magnetic reconnection, magnetic flux ropes form. These flux ropes manifest themselves as sigmoids in the corona. Although there are fundamental reasons to expect such flux ropes to be unstable, the physics is not as simple as might first appear, and there exist various explanations for instability. Many gaps need to be filled in before the relationship between sigmoids and CMEs is well enough understood to be a useful predictive tool     

Phosphorbestimmungsmethoden

Ohne Zusammenfassung     

HOW DOES THE WAY IN WHICH INDIVIDUAL STUDENTS BEHAVE AFFECT THE SHARED CONSTRUCTION OF MEANING?

Audio taped discussions between three students have been examined to shed light on the way in which the behaviour of individual students may affect the shared construction of meaning with graphical calculators. These discussions revealed a complex pattern of interaction between the students. Each student was responsible for defining his or her own role within the discourse and these roles appeared to change as the discussion progressed. With reference to the framework offered by Winbourne and Watson (1998), it is proposed that local communities of practice have been established and that the individual student's positioning within the community of practice determines their success as a learner and contributes towards the creation of shared knowledge.