Surface analysis of steel sheets with GDOS and EPMA

Summary In the field of steel sheet characterization, chemical surface analysis plays a very important role. Surface composition effects the surface properties of the final product. At Voest-Alpine Stahl Linz the analysis techniques GDOS and EPMA are routinely used to characterize the steel sheet surface. Some fundamental experiments are here described for the optimization of GDOS depth resolution. In the documentation for a semiquantitative approach for steel sheet analysis, investigations and experience about minimum detection limits are presented. Self developed methods for concentration mapping and thickness mapping are described in the field of electron probe microanalysis; Also an EPMA depth profiling method is highlighted. Finally practical examples demonstrate the wide application range of the analysis methods.     

Conformational effects on circular dichroism in the photoelectron angular distribution.

The B-spline density-functional method has been applied to the conformers of the (1R, 2R)-1,2-dibromo-1,2-dichloro-1,2-difluoroethane molecule. The cross section, asymmetry, and dichroic parameters relative to core and valence orbitals, which do not change their nature along the conformational curve, have been systematically studied. While the cross section and the asymmetry parameter are weakly affected, the dichroic parameter appears to be rather sensitive to the particular conformer of the molecule, suggesting that this dynamical property could be a useful tool for conformational analysis. The computational method has also been applied to methyl rotation in methyloxirane. Unexpected and dramatic sensitivity of the dichroic-parameter profile to the methyl rotation, both in the core and valence states, has been found. Boltzmann averaging over the conformers reproduces quite closely the profiles previously obtained for the minimum-energy conformation, which is in good agreement with the experimental results.     

Enzymatic resolution of (±)-5-phenyl-4,5-dihydroisoxazole-3-carboxylic acid ethyl ester and its transformations into polyfunctionalised amino acids and dipeptides

Enantiomerically pure (5R)-(?)-5-phenyl-4,5-dihydroisoxazole-3-carboxylic acid ethyl ester was obtained via enzymatic resolution of the corresponding racemic mixture using a lipase from hog pancreas (PPL). The following reduction of the ester group to the corresponding alcohol and the oxidation of the latter led to (5R)-(?)-5-phenyl-4,5-dihydroisoxazole-3-carbaldehyde, and the reaction between this and Schöllkopf’s reagent, (2R)-(+)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine, gave mixtures of adducts with a good syn/anti ratio. The steric configurations of the major diastereoisomer were assigned on the basis of spectroscopic data and X-ray analysis. The subsequent controlled hydrolysis of the pyrazine ring led to β-(5-phenyl-4,5-dihydroisoxazol-3-yl)-serine methyl esters and the corresponding dipeptides with (R)-valine. Finally, reductive cleavage of the 4,5-dihydroisoxazole ring under hydrolytic conditions made it possible to obtain the corresponding polyfunctionalised dipeptides.     

Total neutron cross sections and the nuclear Ramsauer effect (II). En = 0.5–42 MeV

Investigation at fourteen energies from 0.5 to 42 MeV and A 27 shows that a simple expression describes the σ_T(A,E) surface in the energy and mass number region mentioned above. For E 10 MeV the expression can be interpreted by the nuclear Ramsauer effect, while for E < 10 MeV a better approximation for the black-nucleus formula seems to be useful. The constant amplitude of oscillations suggests a weak volume absorption and a strong surface absorption.     

Synthesis of phenyl-substituted 2H-3,4-dihydro-3-aminomethyl-1,4-benzoxazines. Intermediates for 1H-2,3,3a,4-tetrahydroimidazo[5,1-c][1,4]benzoxazin-1-one derivatives. Part II

The synthesis of 2H-3, 4-dihydro-3-aminomethyl-1, 4-benzoxazines substituted by one phenyl group in the 2, 3 or α-position is reported. The two diastereoisomers of the 2-phenyl-derivative were independently synthesized from ethyl trans-3-phenylglycidate by a stereospecific route. A previous attempt at the synthesis of these same compounds gave rise to an unexpected aliphatic-aromatic ketone rearrangement.     

Baker's yeast mediated preparation of carbohydrate-like chiral synthons

Baker's yeast mediated reduction of the α-acetoxy ketones (1)–(3) proceeds with high enantio- and stereoselectivity to give the $\text{anti}$ carbinols (4)–(6), easily converted into the masked chiral deoxy sugars (12)–(14), from which {=D}- and {=L}-deoxysugars have been obtained.     

Fine structure in the mass number dependence of rms charge radii

A comprehensive study of experimental rms charge radii shows that the deviation from the rough $\text{A}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ dependence follows simple trends. For the isotopic sequence of an element, the values of rms radii, normalized by an approximate $\text{A}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ law and plotted as a function of neutron number, lie on or close to straight lines. The slopes of these lines vary systematically as a function of atomic number. There are discontinuities in the values of the slopes for elements that contain N = 20, 28, 50, 82, 88, 90 and 126 neutrons as well as between Z = 8 and 10; a significant change can be found also for the region Z = 76 (N ≈ 114). These changes can be explained qualitatively by the shell model and by the effect of deformation. An “odd-even staggering” of the order of 6 × 10^?4 has also been observed.