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Small volumes of felsic melt, commonly known as oceanic plagiogranites, appear as melt pockets or dikes within the gabbroic section and the sheeted dikes root zone of the oceanic crust. Plagiogranites from the Troodos Ophiolite Complex on Cyprus are among the best exposures of felsic rocks that are embedded in a complete section of obducted oceanic lithosphere. Nevertheless, their exact petrogenesis is still a matter of debate, largely due to limited high-quality trace element and radiogenic isotope data. Previously proposed models for Troodos plagiogranites have included both low-pressure dehydration melting and fractional crystallisation at deeper levels of the oceanic crust. To evaluate both models, oceanic plagiogranites from the Troodos Ophiolite Complex were analysed in this study for their major and trace elements, and for the first time also for Hf–Nd–Sr isotope compositions. The trace element measurements also include for the first time high-precision measurements of high-field-strength element (HFSE) abundances that now permit to better unravel the petrogenesis of the Troodos plagiogranites and their possible mantle sources. In general, the Troodos plagiogranites exhibit a narrow range of Nb/Ta and Zr/Hf that overlap the compositions of mid-ocean ridge basalts (MORB). In line with earlier studies, three compositional groups can be identified: two groups formed by either fractional crystallisation or combined fractional crystallisation and wall rock assimilation, and one group derived from partial melting of slightly altered oceanic crust. The majority of the Troodos plagiogranites (Main Group) are the product of extensive fractional crystallisation of ambient arc-tholeiitic mafic melts. A second group of plagiogranites (Spilia Group) is generated by fractional crystallisation of boninitic precursor melts and the assimilation of arc-tholeiitic crustal material. Variable HFSE concentrations and diagnostic Hf–Nd isotope signatures that are unique to both suites allow discriminating between the two parental melts and fractionation processes. A small group of plagiogranites (Zoopigi Group) is interpreted to derive from partial melting in the conductive layer of active magma chamber lenses (AML). Elevated Nb/Ta, Zr/Hf, and light rare-earth element (LREE) enrichments in these rocks are in support of this model. Collectively, our data suggest that low-pressure fractional crystallisation (also in combination with assimilation of wall rocks) might be the predominant process controlling the formation of felsic rocks on Cyprus, whereas dehydration melting appears to be less important. If compared to Archean tonalitic–trondhjemitic–granodioritic suites (TTGs), compositions of plagiogranites from Cyprus mirror shallow-level processes in thin oceanic crust, which is illustrated by their narrow, MORB-like range of HFSE ratios and their distinct enrichment in heavy rare-earth elements (HREE) that distinguishes them from the Archean TTGs.

Serpentine minerals in Earth's early upper continental crust suppressed atmospheric oxygen levels until the upper crust became granitic.

During the evolution of the Earth, distinct geochemical reservoirs with different Nb/Ta ratios have developed. Archean granitoids of the tonalite–trondhjemite–granodiorite (TTG) suite, which represent the Earth’s early continental crust, show larger Nb/Ta variations than any other Earth reservoir. This implies that significant Nb–Ta fractionation must have occurred during early crust formation, while the underlying mechanism behind is still unclear. Here, we present a new model on how Nb may be fractionated from Ta during partial melting of subducted oceanic crust. Our data show that Nb/Ta ratios in melts derived from rutile- and titanite-bearing eclogite are largely controlled by the modal relative abundances of rutile and titanite in the source. High modal ratios of titanite over rutile generate melts with very high Nb/Ta (>60), whereas low modal titanite/rutile produces melts with much lower Nb/Ta (≤30). Very low Nb/Ta (

Statistical models based on negative binomial and Erlang's distributions have been used to describe the temporal development of the therapeutic effects observed during a clinical study of triacetyl-6-azauridine in psoriasis. The usefulness of such models for the prediction of the time of first appearance of therapeutic or unwanted side-effects during repeated drug administration is discussed.

The antimetabolite 6-azauridine and its triacetate derivative exemplify the problems of developing new drugs for use in man. They showed promising cytostatic properties and very low toxicity in animal experiments. However, they had little effect on human leukemia, although the low toxicity was confirmed in man. They were active against mycosis fungoides and psoriasis. Doses of 6-azauridine well tolerated in all other diseases caused serious early toxic reactions in cases of rheumatoid arthritis. There were other discrepancies between the results of studies in man and animals. — Thein vitro activity against vaccinia virus was confirmed in a controlled clinical trial in smallpox. Promising results were also obtained in patients with ocular herpes simplex. The significance of these results is discussed in terms of the assessment of new drug treatments in man.

In a controlled clinical trial 6-azauridinetriacetate, a drug that inhibits the synthesis of pyrimidine “de novo”, had a therapeutic effect in psoriasis. The general tolerance of the drug is good. However, with the dosage of 150 mg/kg/day the leucocytes and erythrocytes of the peripheral blood may drop after 5–6 weeks, the effect depending on the dosage. 270 mg/kg/day may be administered for several weeks. 400 mg/kg/day have early therapeutic effects but cannot be administered for longer periods because of the side-effects mentioned. Only serious cases of psoriasis should be treated with this drug, as with cytostatics in general.

PEANUTS and cereals may become contaminated with Aspergillus flavus, a mould of which the metabolites (aflatoxins) are potent carcinogens for rat liver1,2. One of these metabolites, aflatoxin B1 is a strong teratogen for the hamster3, but its effect in rats is equivocal4,5. It has been demonstrated that it binds to DNA in vitro and alters RNA metabolism in vivo6.