Stability of Relativistic Matter with Magnetic Fields for Nuclear Charges up to the Critical Value

We give a proof of stability of relativistic matter with magnetic fields all the way up to the critical value of the nuclear charge $Z\alpha=2/\pi$.Comment: LaTeX2e, 12 page

Alveolar weathering basins in granitein Central Portugal: Morphogenesis and typological analysis of weathering forms in levelled landscapes

As bacias de meteorização química de escala média, ou “alvéolos graníticos” quando entendidos no sentido que Alain Godard lhe conferiu, constituem-se como um dos elementos fundamentais na interpretação da morfologia granítica portuguesa, em particular na compreensão da degradação das superfícies aplanadas que são um dos principais traços morfológicos do Portugal Central. Em termos morfológicos, assumem-se como bacias arredondadas, relativamente circunscritas, revestidas por um manto de alteração com espessura variável e com uma dimensão que vai desde as centenas de metros até à dimensão quilométrica.A alveolização é o resultado de um compromisso morfogenético entre fases de alteração química em clima tropical húmido e fases de ablação em clima subtropical seco, pelo que a sua génese se encontra associada a fatores morfoestruturais, enquanto a sua diferenciação se deve, no essencial, a fatores morfoclimáticos. A similaridade das condições de base estruturais nos diferentes sectores do Maciço Hespérico aponta para uma justificação em termos da eficácia dos processos morfogenéticos, em particular da meteorização química, no quadro das diferenças observadas em torno das condições climáticas (atuais e passadas), para a compreensão da manifesta diferença observada entre as formas alveolares do litoral e do interior. A existência de vários tipos de alvéolos – elementares, complexos, corredores de erosão e mistos – mostra que outros fatores, tais como a proximidade do nível de base ou as dimensões das bacias hidrográficas, têm de ser tomados em consideração na compreensão do processo de alveolização no Portugal Central no cenozoico e início do Pleistocénico.</p

An examination of the 4 March 1999 blizzard

© Copyright 2001 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or [email protected]

Phylogenomic test of the hypotheses for the evolutionary origin of eukaryotes

International audienceThe evolutionary origin of eukaryotes is a question of great interest for which many different hypotheses have been proposed. These hypotheses predict distinct patterns of evolutionary relationships for individual genes of the ancestral eukaryotic genome. The availability of numerous completely sequenced genomes covering the three domains of life makes it possible to contrast these predictions with empirical data. We performed a systematic analysis of the phylogenetic relationships of ancestral eukaryotic genes with archaeal and bacterial genes. In contrast with previous studies, we emphasize the critical importance of methods accounting for statistical support, horizontal gene transfer, and gene loss, and we disentangle the processes underlying the phylogenomic pattern we observe. We first recover a clear signal indicating that a fraction of the bacteria-like eukaryotic genes are of alphaproteobacterial origin. Then, we show that the majority of bacteria-related eukaryotic genes actually do not point to a relationship with a specific bacterial taxonomic group. We also provide evidence that eukaryotes branch close to the last archaeal common ancestor. Our results demonstrate that there is no phylogenetic support for hypotheses involving a fusion with a bacterium other than the ancestor of mitochondria. Overall, they leave only two possible interpretations, respectively, based on the early-mitochondria hypotheses, which suppose an early endosymbiosis of an alphaproteobacterium in an archaeal host and on the slow-drip autogenous hypothesis, in which early eukaryotic ancestors were particularly prone to horizontal gene transfers