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K Marthinsen

Publications and source records attributed to K Marthinsen.

6 recordsLinked to original sources
PubMed2005

A study of charge density in copper.

Quantitative convergent-beam electron diffraction (QCBED) experiments allow absolute scale measurements of low-order structure factors with very high accuracy. In this paper, eight low-order structure factors for copper measured by QCBED have been combined with the higher-order gamma-ray structure factors in order to obtain a larger highly accurate experimental data set. The gamma-ray values were relativistically corrected and rescaled. The new data set was then used for studying the charge distribution in copper. Charge deformation maps have been produced and both a maximum-entropy and a multipole analysis have been applied to the data. The result is compared to density functional theory calculations. An almost spherical charge depletion is found around the atomic sites showing typical metal bonding in copper.

Journal Article↗
PubMed2000

Removal of IgG from normal plasma and plasma from untreated patients with active Crohn's disease--effect on levels of contact factors.

Protein G columns were used to remove IgG from human plasma, and the effect on levels of factor XII, factor XI and prekallikrein was studied in functional tests. IgG was detected in PAGE immunoblot experiments with Fc-specific antibodies. Removal of the bulk of IgG in a procedure based on a low plasma dilution (1+2.5) allowed the passage of an IgG fraction along with the contact factors. This fraction was found to be present in higher amounts in plasma from patients with Crohn's disease (n=5) than in control plasma (n=12). In a previous study, PAGE immunoblot experiments showed that part of the prekallikrein was removed along with IgG when a higher plasma dilution (1+10.8) was used (Scand J Clin Lab Invest 1999; 59: 55-64). This observation was supported by results in the present work based on parallel assays with the peptide substrates S-2302 and Bz-Pro-Phe-Arg-pNA. The prekallikrein fraction removed was present in a functional state differing from the main part of prekallikrein by yielding kallikrein with a significantly increased activity against the substrate S-2366. This prekallikrein fraction was present in higher amounts in patient plasma than in control plasma. Part of the corresponding amidase activity was blocked by lima bean trypsin inhibitor, suggesting its presence in association with factor XI. The results also indicated that prekallikrein activator activity was connected with this fraction. With the high dilution procedure an extensive removal of IgG from the patient plasma was obtained compared to the control plasma.

Adult↗
PubMed1999

Use of quantitative convergent-beam electron diffraction in materials science.

Methods for quantitative convergent-beam electron diffraction are outlined and some results of our applications of convergent-beam electron diffraction are shown, with emphasis on quantitative analysis of crystal structures in materials science. Examples of thickness measurements and determination of lattice parameters are presented. Measurements of low-order structure factors to obtain information on bonding charge-density distributions are reviewed, with examples from TiAl intermetallics. For non-centrosymmetric crystals, a method to determine three-phase structure invariants is given. Determination of polarity is also discussed.

Alloys↗
PubMed1999

Three-phase structure invariants and structure factors determined with the quantitative convergent-beam electron diffraction method.

Quantitative convergent-beam electron diffraction is used to determine structure factors and three-phase structure invariants. The refinements are based on centre-disc intensities only. An algorithm for param-eter-sensitive pixel sampling of experimental intensities is implemented in the refinement procedure to increase sensitivity and computer speed. Typical three-beam effects are illustrated for the centrosymmetric case. The modified refinement method is applied to determine amplitudes and three-phase structure invariants in noncentrosymmetric InP. The accuracy of the results is shown to depend on the choice of the initial parameters in the refinement. Even unrealistic starting assumptions and incorrect temperature factor lead to stable results for the structure invariant. The examples show that the accuracy varies from 1 to 10 degrees in the electron three-phase invariants determined and from 0.5 to 5% for the amplitudes. Individual phases could not be determined in the present case owing to spatial intensity correlations between phase-sensitive pixels. However, for the three-phase structure invariant, stable solutions were found.

Journal Article↗
PubMed1990

Functional correlation between kallikrein and factor XII activated in human plasma.

Plasma kallikrein and FXIIa were assayed in acetone-treated human citrated plasma (CPLa) with the chromogenic peptide Bz-Ile-Glu-Gly-Arg-pNA (S-2222) as substrate. In end point assays with short incubation periods (1-10 min.) nearly all kallikrein present could be blocked by a low concentration of soybean trypsin inhibitor (STI). In 30 min. assays the main part of the kallikrein was recovered in a functional state not inhibited by STI, and at the same time the level of FXIIa (as amidase activity blocked by corn inhibitor, C.I.) was reduced to about 2/3 of the initial value. The formation of an association between FXIIa and kallikrein is suggested. In fractions from gel filtration of CPLa kallikrein was assayed as S-2302 amidase, high molecular weight kininogen (HK) was measured in rocket immunoassays, and HK and FXII were studied in PAGE immunoblot experiments. Kallikrein appeared as one peak together with HK (gel mol. wt. 300 KD), about 40% of HK was free (220 KD), and no FXII was observed in the kallikrein or HK peaks, but in two areas corresponding to 78-79 KD and 39-42 KD. When experiments, however, were carried out with plasma acetone-activated and gel filtered in the presence of benzamidine (5 mM), part of the amidase activity present in kallikrein peak fractions was blocked by C.I. This observation supports the above suggestion of an association between FXIIa and kallikrein.

Adult↗