Plutonium-Xenon systematics of Angrites

Introduction: Angrites are igneous meteorites that crystallized very early in the solar system, ~10 Ma after CAIs, as also implied by the presence of now extinct short-lived radionuclides such as 53Mn, 146Sm and 244Pu [1]. Fission Xe was used to calculate 244Pu-136Xeretention ages of eucrites, relative to that of Angra dos Reis (AdoR) [2]. AdoR has an absolute Pb-Pb age of 4557.8 Ma [see 1 for ref.]. Most eucrites, being as old as angrites, experienced various parent body processes leading to ages ranging from ~20 Ma before, to ~100 Ma after AdoR [2]. Angrites, however, remained largely unaltered after differentiation. Here, we examine whether Xe isotopic characteristics allow determining an age sequence for angrites

The trapped heavy noble gases in recently found Martian meteorites

The composition of the trapped Ar, Kr, and Xe in the Martian meteorites Los Angeles, Say Al Uhaymir 005/008, and 094 is discussed and found to be consistent with a mixture of Martian mantle and atmosphere noble gases and terrestrial contamination

The pre-atmospheric size of Martian meteorites

The pre-atmospheric size of martian meteorites was calculated based on 80Kr produced by epithermal secondary cosmic-ray produced neutrons of 30-300 eV energy. For seven meteorites we obtained minimum radii of 22-27 cm, corresponding to 150-270 kg

Solar noble gases in the Angrite parent body – Evidence from volcanic volatiles trapped in D'Orbigny glass

We compare the noble gases in D'Orbigny glass and bulk. The glass was formed after the bulk silicates and contains interior solar noble gases that may originate from early volcanic activity on the angrite parent body, trapped upon fast cooling

The ingredients of the “Subsolar” noble gas component

On the basis of several experiments on separates of the EH5 chondrite St. Mark–s, we will argue that the 'subsolar' noble gas component is a mixture of solar-like, Q- and terrestrial noble gases

Characterization of the noble gases and CRE age of the D'Orbigny angrite

Introduction: The D’Orbigny angrite, a 16.55 kg stone, was found 1979 in Argentina [1]. Mineralogy and chemistry of this meteorite were characterized in detail [2-6]. A Pb-U-Th age of 4.559 Ga was obtained for pyroxenes by Jagoutz et al. [7]. Here we report results on the noble gas isotopic composition and, in particular, on the cosmic-ray exposure (CRE) age of D’Orbigny

I-Xe analysis of a magnetic separate from Lodranite GRA95209

I-Xe dating of a magnetic mineral separate from lodranite GRA95209 suggests that peak temperatures (and therefore melt migration) occurred early, at least a few million years before closure of the I-Xe system in phosphates from Acapulco

A simple method for estimating a cow's breeding value from her own lactations and her sire's progeny test

International audienc

Analyses of six homologous proteins of Protochlamydia amoebophila UWE25 encoded by large GC-rich genes (lgr): a model of evolution and concatenation of leucine-rich repeats

BACKGROUND: Along the chromosome of the obligate intracellular bacteria Protochlamydia amoebophila UWE25, we recently described a genomic island Pam100G. It contains a tra unit likely involved in conjugative DNA transfer and lgrE, a 5.6-kb gene similar to five others of P. amoebophila: lgrA to lgrD, lgrF. We describe here the structure, regulation and evolution of these proteins termed LGRs since encoded by "Large G+C-Rich" genes. RESULTS: No homologs to the whole protein sequence of LGRs were found in other organisms. Phylogenetic analyses suggest that serial duplications producing the six LGRs occurred relatively recently and nucleotide usage analyses show that lgrB, lgrE and lgrF were relocated on the chromosome. The C-terminal part of LGRs is homologous to Leucine-Rich Repeats domains (LRRs). Defined by a cumulative alignment score, the 5 to 18 concatenated octacosapeptidic (28-meric) LRRs of LGRs present all a predicted alpha-helix conformation. Their closest homologs are the 28-residue RI-like LRRs of mammalian NODs and the 24-meres of some Ralstonia and Legionella proteins. Interestingly, lgrE, which is present on Pam100G like the tra operon, exhibits Pfam domains related to DNA metabolism. CONCLUSION: Comparison of the LRRs, enable us to propose a parsimonious evolutionary scenario of these domains driven by adjacent concatenations of LRRs. Our model established on bacterial LRRs can be challenged in eucaryotic proteins carrying less conserved LRRs, such as NOD proteins and Toll-like receptors

Alpine vascular plant species richness: the importance of daily maximum temperature and pH

Species richness in the alpine zone varies dramatically when communities are compared. We explored (i) which stress and disturbance factors were highly correlated with species richness, (ii) whether the intermediate stress hypothesis (ISH) and the intermediate disturbance hypothesis (IDH) can be applied to alpine ecosystems, and (iii) whether standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone. Species numbers and standing crop were determined in 14 alpine plant communities in the Swiss Alps. To quantify the stress and disturbance factors in each community, air temperature, relative air humidity, wind speed, global radiation, UV-B radiation, length of the growing season, soil suction, pH, main soil nutrients, waterlogging, soil movement, number of avalanches, level of denudation, winter dieback, herbivory, wind damage, and days with frost were measured or observed. The present study revealed that 82% of the variance in␣vascular species richness among sites could be explained by just two abiotic factors, daily maximum temperature and soil pH. Daily maximum temperature and pH affect species richness both directly and via their effects on other environmental variables. Some stress and disturbance factors were related to species richness in a monotonic way, others in an unimodal way. Monotonic relationships suggest that the harsher the environment is, the fewer species can survive in such habitats. In cases of unimodal relationships (ISH and IDH) species richness decreases at both ends of the gradients due to the harsh environment and/or the interaction of other environmental factors. Competition and disturbance seemed only to play a secondary role in the form of fine-tuning species richness in specific communities. Thus, we concluded that neither the ISH nor the IDH can be considered useful conceptual models for the alpine zone. Furthermore, we found that standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone, even though there is no direct causalit