Emissionsspektrometrische Analyse von Roheisen

Zusammenfassung Die spektrometrische Analyse von weiß erstarrtem Roheisen (auf C, Si, Mn, P, S, Cu) ist mit der gleichen Anregung und in der gleichen Funkzeit wie diejenige von Stahl möglich. Eine spezielle Kalibriertechnik mit Stahlproben garantiert ein ausreichend reproduzierbares und richtiges Resultat in relativ kurzer Zeit (20 sec).

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Emission-spectrometrical analysis of pig iron

The conditions of pig iron analysis by using a direct reading spectrometer for routine determination of C, Si, Mn, P, S and Cu, the influence of sampling and a new calibration technique of the instrument are described. The whole time needed for complete spectrometrical analysis is about 20 sec.

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Wir sind Herrn T. Nientiedt für zahlreiche Anregungen und Diskussionen zu Dank verpflichtet.     

Trimethylsilylverbindungen der Vb-Elemente. VI. Synthese,Molekül- und Kristallstruktur des Tetrakis(trimethylsilyl)distibans im Vergleich mit Tetraphenyldistiban

Trimethylsilyl Derivatives of Vb-Elements. VI. Synthesis, Molecular and Crystal Structure of Tetrakis(trimethylsilyl)distibine Compared with Tetraphenyldistibine Tetrakis(trimethylsilyl)distibine already isolated by Breunig et al. [9] from cleavage reactions of tris(trimethylsilyl)stibine may also be obtained in high yields from lithium bis(trimethylsilyl)antimonide · 2THF and 1,2-dibromoethane in n-pentane. This compound intensely red in the solid state, but only slightly yellow in solution or in the melt crystallizes in the monoclinic space group P2₁/c with a = 680.6(1); b = 1672.8(2); c = 1190.0(1) pm; β = 119.01(5)°; Z = 2 at +20°C. An X-ray structure determination (R = 0.017) shows the bis(trimethylsilyl)-stibino groups to be arranged in a transoid position. Characteristic bond lengths and angles are: Sb? Sb 286.7(1); Sb? Si 259.4 pm; Si? Sb? Si 94.46(3); Sb? Sb? Si 98.68(3) and 94.43(3)°. As in similiar 2,2′,5,5′-tetramethyldistibolyl published recently by Ashe III et al. [8] this crystal structure, too, is characterized by a nearly linear sequence of Sb? Sb groups. Compared with the sum of van-der-Waals radii the intermolecular Sb-Sb contact in such a chain is shortened from 440 to 399 pm. This probably allows electronic interactions of unknown type responsible for the colour of the crystals. In keeping with this assumption an analogous formation of chains is not found in solid, only yellow tetraphenyldistibine 5 the structure of which has already been studied by Rehder et al. [44].     

Eine neue Untersuchungstechnik in der Metallanalyse

A method, named “cold oxidation” was developed, by which structures of isotropic looking pyrocarbon coatings of nuclear fuel particles can be made visible. It is based on a dry oxidation of the pyrocarbon at room temperature by highly excited oxygen. The amorphous parts of the pyrocarbon coatings burn off more quickly than the pyrocarbon itself and thereby a relief-like coating structure appears. It could be shown that a connection exists between the structure of the pyrocarbon coatings after “cold oxidation” and their behaviour under fast neutron irradiation.     

Cytotoxicity and Antiproliferative Effect of Hypericin and Derivatives after Photosensitization

The toxicity on three human tumor cell lines (A431, HeLa and MCF7) of five phenanthroperylenequinones (hypericin and derivatives) and two perylenequinones (cercosporin and calphostin C) was investigated after photosensitization (4 J/cm²). Furthermore, the antiproliferative effect on HeLa cells was studied for the phenanthroperylenequinones. Hypericin, 2,5-dibromohypericin, 2,5,9,12-tetrabromohypericin and perylenequinones displayed a potent cytotoxic and antiproliferative effect in the nanomolar range. Hypericin dicarboxylic acid exhibited no photoactivity. In general, the antiproliferative activity correlated well with the photocytotoxicity. However, the nonphotocytotoxic compound hexamethylhypericin showed potent antiproliferative activity in the nanomolar range, probably exerting its action by protein kinase C inhibition. Without light irradiation, no cytotoxic and antiproliferative effect was observed for any photocytotoxic phenanthroperylenequinone compound. Furthermore, confocal laser microscopy revealed that the subcellular localization in A431 cells was similar for the photoactive compounds; the photosensitizers were mainly concentrated in the perinuclear region, probably corresponding with the Golgi apparatus and the endoplasmic reticulum. In addition, the accumulation of the photosensitizers in HeLa cells was investigated. All compounds except hypericin dicarboxylic acid were found to concentrate to a large extent in the cells. The compound 2,5,9,12-tetrabromohypericin seemed intrinsically more effective than hypericin since the intracellular concentration of the bromoderivative was a magnitude of order lower than that of hypericin although both compounds showed similar photobiological activity.     

The electrochemistry of strapped and capped porphyrin monomers,mono- and doubly-linked dimers,and their Zn and Mg complexes

The interaction between two “spatially close” porphyrins plays important roles in biochemical functions. The present study focuses on the effects of distortion, steric hindrance, distance and orientation exerted by a variety of porphyrin monomers (strapped and capped) and dimers (mono- and doubly-linked) on their redox properties as well as the stability of positively charged intermediates derived from them. Cyclic voltammograms have been conducted in aprotic media on both free bases and their metal complexes (Zn and Mg). The effect of the nature of supporting electrolyte on the anodic peak potentials and wave separation has been studied in the case of conjugated directly-linked bis-zinc and bis-magnesium porphyrins.     

Hyperfine structure of the 625 nm band in the a 3Πu ← X 1 Σg transitions of Na2

Hyperfine structures of transitions in the a ³Π_u ← X¹Σ_g system of Na₂ have been accurately measured by Doppler-free laser excitation spectroscopy in a collimated molecular beam. The hyperfine patterns are quantitatively explained and the reduced matrix elements of the magnetic dipole hf interaction determined from a least-squares fit to the measured line positions.