Datierung von Ostseesedimenten mit 210Pb

The paper reports on the results of²¹⁰Pb measurement in sediment cores from the Baltic Sea. The models used for the interpretation are derived and discussed. In general, the sedimentation parameters calculated with different models are consistent. However, parameters of cores independently taken on same stations partly show clearly differing values. The reasons of this observation has to be analysed by further studies.

An essential problem considered in this paper is the dating of disturbed sediments. The use of such cores for the reconstruction of the input history of chemical indicators requires a deconvolution of data. The response function necessary for this procedure can be derived from ²¹⁰Pb measurements. The results of such a reconstruction considerably differ from those obtained by conventional dating models. The analysis of the measuring uncertainty of the indicator (e.g. lead) in the deconvolution procedure unveals the limits of the method and prevents it from overinterpretation.     

Ein α-Spektrometcr für Untersuchungen mit Umweltnukliden

Es wird ein einfaches α-Spektrometer mit einem Halbleiterdelektor beschrieben, das für die Messung von Umweltnykliden entwickelt wurde. Zur Anpassung an unterschiedliche Meßaufgaben kann die Meßgeometrie durch Variation des Präparat-Detektor-Abslandes und durch Einbau von Blenden verändert werden. Dabei ist eine gewählte Meßgeometrie mit hoher Genauigkeit reproduzierbar. Die Nachweisgrenze des α-Spektrometers beträgt bei einer Meßzeit von 4 · 10⁵ s etwa 2,3 mβq, das entspricht 0,18 μg U bzw, 0,55 μg Th.     

Resonance Raman detection of carotenoid antioxidants in living human tissues

We have used resonance Raman scattering as a novel noninvasive optical technology to measure carotenoid antioxidants in living human tissues of healthy volunteers. By use of blue-green laser excitation, clearly distinguishable carotenoid Raman spectra superimposed on a fluorescence background are obtained. The Raman spectra are obtained within less than a minute, and the required laser light exposure levels are well within safety standards. Our technique can be used for rapid screening of carotenoid levels in large populations and may have applications for assessing antioxidant status and the risk for diseases related to oxidative stress.     

Optical properties and stable,broadly tunable cw laser operation of new FA-type centers in Tl+-doped alkali halides

A new group of complex color centers with F_A-type properties, involving simple center production and high thermal and optical stabilities, has been found in six Tl⁺-doped alkali halides: NaCl, KCl, RbCl, KBr, RbBr and RbI. In its first tested examples, KCl and KBr, broadly tunable cw laser operation over the 1.4 to 1.7 μm range has been obtained, with output powers in the 100 mW range. In contrast to already existing F⁺₂ and F⁺₂-like centers, operating in the same wavelength range, the new F_A(Tl⁺) lasers are optically stable and do not show any bleaching effects under laser operation.     

tert‐Butyldiphenylsilylhydrazin – ein Baustein für Tetrakis‐silylhydrazine,Silylhydrazone und O‐Silylpyrazolone

tert ‐Butyldiphenylsilylhydrazine – Precursors for Tetra(silyl)hydrazines, Silylhydrazones, and O‐Silylpyrazolones tert‐Butylchlorodiphenylsilane reacts with hydrazine in presence of triethylamine to give the mono(silyl)hydrazine Me₃CSiPh₂NHNH₂ ( 1 ). The lithium derivative of 1 ( 1 a ) forms the N,N′‐bis(silyl)hydrazines 2 and 3 in the reaction with chlorosilanes. ( 2 : Me₃CSiPh₂NHNHSiPh₂CMe₃; 3 : Me₃CSiPh₂NHNHSiMe₂CMe₃). The monomeric dilithiumhydrazide 4 , (Me₃CSiPh₂)₂N₂Li₂(THF)₃, is obtained from 2 and the bimolar amount of C₄H₉Li in THF. 4 reacts with an excess of SiF₄ to give the tetra(silyl)hydrazine 5 , Me₃CSiPh₂(SiF₃)N–N(SiF₃)SiPh₂CMe₃. 1 and ketones undergo condensation to silylhydrazones, Me₃CSiPh₂NHN=C(Me)R ( 6 : R = Me; 7 : R = CMe₃), with elimination of H₂O. Only one of the two possible isomers of 7 is formed. Cis/trans isomers ( 8 a , b ) are obtained in the analogous reaction of 1 and ethyl acetoacetate, Me₃CSiPh₂NH–N=CMe–CH₂–COOEt ( 8 a , b ). 8 condenses thermally with elimination of EtOH and formation of the O‐silylpyrazolone 9 , Me₃CSiPh₂O–(C=N–NH–CMe=CH–). The results of the crystal structure analysis of the compounds 2 , 4 , and 7 are reported.     

Experimental study of uranium isotope fractionation of rock material from two aquifers

This paper presents results of a study carried out in order to estimate the uranium isotope fractionation ²³⁴U/²³⁸U in groundwater from laboratory experiments. Matrix rock from borcholes in a Triassic sandstone aquifer and a Pleistocene sand aquifer was leached with 1 N HCl, 0.1 N HCl and deionized water.

Additionally, the uranium isotope composition of the bulk rock (index “R”) and several groundwater samples of corresponding horizons were analysed. The results indicate the relation between the portion of leached uranium (index “L”) and the observed activity ratio ²³⁴U/²³⁸U (AU)

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If this relation can be confirmed by further investigations new possibilities of using uranium isotopes in hydrogeology would be made available

Die Arbeit stellt Ergebnisse einer Studie vor, die zur Abschützung der Uranium-Isotopenfraktionierung ²³⁴U/²³⁸U im Grundwasser aus Laborexperimenten durchgeführt wurde. Matrixgestein von Bohrlöchern in einem Triassischen Sandstein-Grundwasserleiter und einem aus pleislozänen Sanden bestehenden Grundwasserleiter wurde mit 1 N HCl, 0,1 HCl und entionisiertem Wasser gelaugt. Auβerdem wurden die Uranium-Isotopenzusammensetzung des Gesteins (Index “R”) und einige Grundwasserproben zugehöriger Horizonte analysiert. Die Ergebnisse zeigen cine Beziehung zwischen dem Anteil des gelaugten Uraniums (Index “L”) und dem Aktivitätsverhältnis ²³⁴U/²³⁸U (AU)

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Wenn diese Relation durch weitere Untersuchungen bestäligt werden kann, eröffnen sich neue Möglichtkeiten für die Nutzung der Uraniumisotope in der Hydrogeologie.     

32Si in precipitation of Freiberg /GDR/

New results of³²Si measurements in precipitation of Freiberg /GDR/ are presented and discussed with regard to the³²Si initial concentration for groundwater dating.