Sulphur and oxygen isotopic characters of dissolved sulphate in groundwater from the Pleistocene aquifer in the southern Jordan Valley (Jericho area, Palestine)

Sulphate and chloride concentrations in the shallow Pleistocene aquifer systems in the lower Jordan valley area indicate a general trend of increasing salinity eastward and southward. This study was conducted in one of the important sub-basins feeding the Pleo-Pleistocene aquifer in the Jericho area in the southern part of the valley using S and O isotopes of dissolved sulphate. The results show that sulphate has mainly two contributions to the groundwater. One is the surface seepage, which is present as a salty leachate form with the positive delta34Ssulphate values of primary gypsum in Lisan and Samara formations, and the second is the upwelling saline water which was in contact with a deep secondary gypsum, aragonites and salty rocks and rose up under heavy abstraction with depleted 34S in sulphate and relatively high sulphate and chloride content. The latest was clearly shown in the Arab Project wells to the east that is undergoing a continuous heavy abstraction. The isotopic signatures of S and O in these wells to the east show that this depleted 34S and highly concentrated sulphate might also indicate a dissolved sulphate originating from pyrite oxidation that results from the interaction with a pyrite-rich aquifer, which can well up with salty water under heavy abstraction and is oxidised in the upper aerobic shallow aquifer.     

Stereoselective synthesis of highly functionalized thiopeptide thiazole fragments from uronic acid/cysteine condensation products: access to the core dipeptide of the thiazomycins and nocathiacins

We present the stereoselective synthesis of various highly functionalized thiazole dipeptides that are found in thiopeptide antibiotics like thiazomycins and nocathiacins. The condensation of an uronic acid with l-cysteine methyl ester delivers along two different protocols the stereopure thiazolidine lactones or lactams on the multigram scale, respectively. Oxidation of the thiazolidine moiety to the thiazole and tailoring of the sugar chains yield the thiazole dipeptide as present in the core motif of the thiopeptide antibiotics, as well as its epimer and a homolog. The modular assembly of the potent natural products and their analogs relies on the synthetic accessibility of adequately protected building blocks of tailored absolute stereochemistry.     

Measurement of the noise generation at the trailing edge of porous airfoils

Owls are commonly known for their quiet flight, enabled by three adaptions of their wings and plumage: leading edge serrations, trailing edge fringes and a soft and elastic downy upper surface of the feathers. In order to gain a better understanding of the aeroacoustic effects of the third property that is equivalent to an increased permeability of the plumage to air, an experimental survey on a set of airfoils made of different porous materials was carried out. Several airfoils with the same shape and size but made of different porous materials characterized by their flow resistivities and one non-porous reference airfoil were subject to the flow in an aeroacoustic open jet wind tunnel. The flow speed has been varied between approximately 25 and 50 m/s. The geometric angle of attack ranged from −16° to 20° in 4°-steps. The results of the aeroacoustic measurements, made with a 56-microphone array positioned out of flow, and of the measurements of lift and drag are given and discussed.     

On the normalizer of finitely generated subgroups of absolute galois groups of uncountable hilbertian fields of characteristic 0

For a fieldK and a positive integere let N _e (K) be the set of alle-tuplesσ = (σ ₁, …,σ _e)εG(K) ^e that generate a selfnormalizer closed subgroup ofG(K). Chatzidakis proved, that ifK is Hilbertian and countable, then N _e (K) has Haar measure 1. IfK is Hilbertian and uncountable, this need not be the case. Indeed, we prove that ifK ₀ is a field of characteristic 0 that contains all roots of unity,T is a set of cardinality ℵ₁ which is algebraically independent overK ₀ andK =K ₀(T), then neither N _e (K) nor its complement contain a set of positive measure. In particular N _e (K) is a nonmeasurable set. This work was partially supported by an NSF grant #DMS-H603187, while the second author enjoyed the hospitality of Rutgers University.     

Chlorophyll fluorescence biosensor for the detection of herbicides

A biosensor is described for the detection of triazine and phenylurea herbicides in drinking water by kinetic measurements of endogenous chlorophyll fluorescence in isolated chloroplasts from higher plants. The pocket-size device uses a diode laser for simultaneous excitation of sample and reference channels, and photodiodes for detection of the emitted light. The biological material can be supplied as a freeze-dried powder, stable for 21 days at room temperature, for 6 weeks at 4 ( degrees )C or for at least 9 months at -20 ( degrees )C. The detection of 0.1 microg/l of a single herbicide, as required by European Community legislation on drinking water quality, can be achieved without prior extraction of the sample.     

Bestimmung von Sauerstoff in Molybd?n, Wolfram und Rhenium nach dem Wasserstoffreduktionsverfahren

Zusammenfassung Gegenüber dem universell einsetzbaren Hei\extraktionsverfahren besteht der Hauptvorteil des Wasserstoffreduktionsverfahrens in dem geringen apparativen Aufwand. Aus der Umsetzung des bei der Reduktion gebildeten Wassers mit Calciumhydrid resultiert obendrein eine hohe Empfindlichkeit des Wasserstoffreduktionsverfahrens. Dies bedeutet, da\ — im Gegensatz zu den anderen Varianten des Wasserstoff-reduktionsverfahrens — auch für Sauerstoffgehalte unter 0,01% Probenmengen von etwa 1 g ausreichend sind.

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Summary A method is described for the determination of oxygen in molybdenum, tungsten, and rhenium by reduction with hydrogen. The water formed is then reacted with calcium hydride to give hydrogen which is determined by gas volumetry. In contrast to the generally applicable hot-extraction the main advantage of the reduction procedure is the less expensive equipment. Moreover, the reaction of the water with calcium hydride results in a high sensitivity of the method. Sample weights of about 1 g are sufficient, also for oxygen contents below 0.01%.

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Teil der Dissertationsarbeit von K. Friedrich.

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Herrn Prof. Dr. habil. E. Rexer möchten wir für die Förderung der Arbeit danken. Weiterhin sind wir besonders Herrn Dr. rer. nat. G. Ehrlich für anregende Diskussionen zu Dank verpflichtet.