Analytical quality control by solid sampling GFAAS in the production of animal tissue reference materials: lead and cadmium in bovine liver reference materials

Summary The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of bovine liver reference material is described. Analytical quality assurance was achieved by using a wet digestion decomposition procedure and GFAAS (WD-GFAAS) as well as three different methods of SS-GFAAS. It will be shown, that SS-GFAAS is an adequate and efficacious method of analytical quality control in the production of reference materials. Details are given about the preliminary steps of sample selection and preparation, applying SS-GFAAS both as a screening method and for the detection of contamination during the production of the reference materials. The element contents of the four bovine liver materials measured after decomposition with nitric acid in the open system by GFAAS and also by Flame-AAS, using the slotted tube atom trap, are compared statistically with the results obtained by SS-GFAAS. In solid sampling analyses three different systems were applied: a solid sampling ZAA-spectrometer with platform-boat, a D₂AA-spectrometer with solid sampling graphite tube and platform-drawer and an autoprobe-D₂AA-spectrometer with solid sampling autoprobe and graphite tube.     

Triphenylphosphan-Nickel(0)-Komplexe mit Isocyanid-Liganden — [(RNC)nNi(PPh3)4–n] (n = 1–3)

Triphenylphosphane Nickel(0) Complexes with Isocyanide Ligands — [(RNC)_nNi(PPh₃)_4–n] (n = 1–3) Synthesis and properties of the isocyanide triphenylphosphane nickel(0) complexes [(RNC)Ni(PPh₃)₃], [(RNC)₂Ni(PPh₃)₂] and [(RNC)₃Ni(PPh₃)] (R = ^tBu, Cy, PhCH₂, p-TosCH₂) are described. I.r. and ³¹P n.m.r. spectra were recorded and the X-ray crystal structure of [(PhCH₂NC)₂Ni(PPh₃)₂] was determined.     

Über die Uranylverbindungen des Natrium-cyklohexyldithiocarbaminats

Zusammenfassung Na-cyklohexyldithiocarbaminat reagiert im p_H-Bereich 6,6 bis 7,2 mit Uranylsalzen unter Bildung eines in Wasser mit gelber Farbe lösliehen Komplexes, der bei p_H 6,6 ein Absorptionsmaximum bei 392 bis 394 nm besitzt. Die wäßrige Lösung wird durch Zusatz von Alkalilauge bis zum p_H 8 bis 9 momentan entfärbt.Es wird ein Kaliumdoppelsalz KUO₂(S₂HCNC₆H₁₁)₃ · 3 H₂O beschrieben; ferner wird über die Umwandlung des Calciumdoppelsalzes beim Kochen mit NaOH berichtet.

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Summary Sodium cyolohexyldithiooarbamate reacts, in the p_H range 6.6 to 7.2, with uranium salts to yield a complex which gives a yellow aqueous solution. The absorption maximum is at 392–394 nm at p_H 6.6. The aqueous solution loses its color immediately when caustic alkali is added to raise the p_H to 8 or 9.A potassium double salt, KUO₂(S₂HCNC₆H₁₁)₃ · 3 H₂O is described. A report is also given of the transformation of the calcium double salt on boiling with NaOH.

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Résumé Le dithiocarbamate de cyclohexylsodium réagit dans le domaine de p_H 6,6 à 7,2 sur les sels d'uranyle avec formation d'un complexe coloré en jaune, soluble dans l'eau, qui possède à p_H 6,6 un maximum d'absorption pour 392–394 nm. Par addition de lessive alcaline jusqu'à p_H 8 à 9 on décolore momentanément la solution aqueuse.On décrit un sel double de potassium KUO₂(S₂HCNC₆H₁₁)₃ · 3 H₂O; on rend compte, de plus, de la transposition du sel double de calcium par chauffage avec la soude.

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Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich.     

Ohmic and step noise from a single trapping center hybridized with a Fermi sea

We show that single electron tunneling devices such as the Cooper-pair box or double quantum dot can be sensitive to the zero-point fluctuation of a single trapping center hybridized with a Fermi sea. If the trap energy level is close to the Fermi sea and has linewidth gamma > k(B)T, its noise spectrum has an Ohmic Johnson-Nyquist form, whereas for gamma < k(B)T the noise has a Lorentzian form expected from the semiclassical limit. Trap levels above the Fermi level are shown to lead to steps in the noise spectrum that can be used to probe their energetics, allowing the identification of individual trapping centers coupled to the device.     

Layer-resolved magnetic moments in Ni/Pt multilayers

The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically "dead" Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.     

Absence of intrinsic ferromagnetic interactions of isolated and paired Co dopant atoms in Zn1-xCoxO with high structural perfection

We report element specific structural and magnetic investigations on Zn(1-x)Co(x)O epitaxial films using synchrotron radiation. Co dopants exclusively occupy Zn sites as revealed by x-ray linear dichroism having an unprecedented degree of structural perfection. Comparative magnetic field dependent measurements by x-ray magnetic circular dichroism and conventional magnetometry consistently show purely paramagnetic behavior for isolated Co dopant atoms with a magnetic moment of 4.8 (mu B). However, the total magnetization is reduced by approximately 30%, demonstrating that Co-O-Co pairs are antiferromagnetically coupled. We find no sign of intrinsic ferromagnetic interactions for isolated or paired Co dopant atoms in Co:ZnO films.     

Spectral properties for a class of continuous state branching processes with immigration

We explicitly construct nontrivial invariant probability measures for a class of continuous state branching processes with immigration. The class of these measures include random Gamma measures and path space measures of Lévy subordinators as particular examples. Using the explicit construction we study long-time behaviour and hypercontractivity of the transition semigroups in corresponding L²-spaces.     

Metallic state in cubic FeGe beyond its quantum phase transition

We report on results of electrical resistivity and structural investigations on the cubic modification of FeGe under high pressure. The long-wavelength helical order (T(C) = 280 K) is suppressed at a critical pressure p(c) approximately 19 GPa. An anomaly at T(X)(p) and strong deviations from a Fermi-liquid behavior in a wide pressure range above p(c) suggest that the suppression of T(C) disagrees with the standard notion of a quantum critical phase transition. The metallic ground state persisting at high pressure can be described by band-structure calculations if zero-point motion is included. The shortest FeGe interatomic distance display discontinuous changes in the pressure dependence close to the T(C)(p) phase line.