Habitability of the Goldilocks Planet Gliese 581g: Results from Geodynamic Models

Aims: In 2010, detailed observations have been published that seem to indicate another super-Earth planet in the system of Gliese 581 located in the midst of the stellar climatological habitable zone. The mass of the planet, known as Gl 581g, has been estimated to be between 3.1 and 4.3 Earth masses. In this study, we investigate the habitability of Gl 581g based on a previously used concept that explores its long-term possibility of photosynthetic biomass production, which has already been used to gauge the principal possibility of life regarding the super-Earths Gl 581c and Gl 581d. Methods: A thermal evolution model for super-Earths is used to calculate the sources and sinks of atmospheric carbon dioxide. The habitable zone is determined by the limits of photosynthetic biological productivity on the planetary surface. Models with different ratios of land / ocean coverage are pursued. Results: The maximum time span for habitable conditions is attained for water worlds at a position of about 0.14+/-0.015 AU, which deviates by just a few percent (depending on the adopted stellar luminosity) from the actual position of Gl 581g, an estimate that does however not reflect systematic uncertainties inherent in our model. Therefore, in the framework of our model an almost perfect Goldilock position is realized. The existence of habitability is found to critically depend on the relative planetary continental area, lending a considerable advantage to the possibility of life if Gl 581g's ocean coverage is relatively high. Conclusions: Our results are a further step toward identifying the possibility of life beyond the Solar System, especially concerning super-Earth planets, which appear to be more abundant than previously surmised.Comment: 5 pages, 3 figures, 1 table; in pres

The habitability of super-Earths in Gliese 581

Aims: The planetary system around the M star Gliese 581 consists of a hot Neptune (Gl 581b) and two super-Earths (Gl 581c and Gl 581d). The habitability of this system with respect to the super-Earths is investigated following a concept that studies the long-term possibility of photosynthetic biomass production on a dynamically active planet. Methods: A thermal evolution model for a super-Earth is used to calculate the sources and sinks of atmospheric carbon dioxide. The habitable zone is determined by the limits of biological productivity on the planetary surface. Models with different ratios of land / ocean coverage are investigated. Results: The super-Earth Gl 581c is clearly outside the habitable zone, since it is too close to the star. In contrast, Gl 581d is a tidally locked habitable super-Earth near the outer edge of the habitable zone. Despite the adverse conditions on this planet, at least some primitive forms of life may be able to exist on its surface.Therefore, Gl 581d is an interesting target for the planned TPF/Darwin missions to search for biomarkers in planetary atmospheres.Comment: 6 pages, 4 figures, 2 table

The Makeenko-Migdal equation for Yang-Mills theory on compact surfaces

We prove the Makeenko-Migdal equation for two-dimensional Euclidean Yang-Mills theory on an arbitrary compact surface, possibly with boundary. In particular, we show that two of the proofs given by the first, third, and fourth authors for the plane case extend essentially without change to compact surfaces.Comment: Final version, minor typographical corrections. To appear in Comm. Math. Phy

Atomic data from the Iron Project.XLIII. Transition probabilities for Fe V

An extensive set of dipole-allowed, intercombination, and forbidden transition probabilities for Fe V is presented. The Breit-Pauli R-matrix (BPRM) method is used to calculate 1.46 x 10^6 oscillator strengths for the allowed and intercombination E1 transitions among 3,865 fine-structure levels dominated by configuration complexes with n <= 10 and l <= 9. These data are complemented by an atomic structure configuration interaction (CI) calculation using the SUPERSTRUCTURE program for 362 relativistic quadrupole (E2) and magnetic dipole (M1) transitions among 65 low-lying levels dominated by the 3d^4 and 3d^ 4s configurations. Procedures have been developed for the identification of the large number of fine-structure levels and transitions obtained through the BPRM calculations. The target ion Fe VI is represented by an eigenfunction expansion of 19 fine-structure levels of 3d^3 and a set of correlation configurations. Fe V bound levels are obtained with angular and spin symmetries SL\pi and J\pi of the (e + Fe VI) system such that 2S+1 = 5,3,1, L <= 10, J <= 8 of even and odd parities. The completeness of the calculated dataset is verified in terms of all possible bound levels belonging to relevant LS terms and transitions in correspondence with the LS terms. The fine-structure averaged relativistic values are compared with previous Opacity Project LS coupling data and other works. The 362 forbidden transition probabilities considerably extend the available data for the E2 and M1 transtions, and are in good agreement with those computed by Garstang for the 3d^4 transitions.Comment: 19 pages, 1 figure. This paper marks the beginning of a large-scale effort of ab initio atomic calculations that should eventually lead to re-calculation of accurate iron opacities. Astron. Astrophys. Suppl. Ser. (in press

Habitability of Super-Earths: Gliese 581c and 581d

The unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses smaller than 10 Earth masses. Unlike the larger exoplanets previously found, these smaller planets are more likely to have a similar chemical and mineralogical composition to the Earth. We present a thermal evolution model for super-Earth planets to identify the sources and sinks of atmospheric carbon dioxide. The photosynthesis-sustaining habitable zone (pHZ) is determined by the limits of biological productivity on the planetary surface. We apply our model to calculate the habitability of the two super-Earths in the Gliese 581 system. The super-Earth Gl 581c is clearly outside the pHZ, while Gl 581d is at the outer edge of the pHZ. Therefore it could at least harbor some primitive forms of life.Comment: 3 pages, 1 figure; submitted to: Exoplanets: Detection, Formation and Dynamics, IAU Symposium 249, eds. Y.-S. Sun, S. Ferraz-Mello, and J.-L. Zhou (Cambridge: Cambridge University Press

Origin and roles of a strong electron-phonon interaction in cuprate oxide superconductors

A strong electron-phonon interaction arises from the modulation of the superexchange interaction by phonons. As is studied in Phys. Rev. B 70, 184514 (2004), Cu-O bond stretching modes can be soft around (pm pi/a, 0) and (0, pm pi/a), with a the lattice constant of CuO_2 planes. In the critical region of SDW, where antiferromagnetic spin fluctuations are developed around nesting wave numbers Q of the Fermi surface, the stretching modes can also be soft around 2Q. Almost symmetric energy dependences of the 2Q component of the density of states, which are observed in the so called stripe and checker-board states, cannot be explained by CDW with 2Q following the complete softening of the 2Q modes, but they can be explained by a second-harmonic effect of SDW with Q. The strong electron-phonon interaction can play no or only a minor role in the occurrence of superconductivity.Comment: 5 pages, 1 fugur

Genetic control of sensory neuron diversification

The somatosensory system of vertebrates transmits information from external and internal environments to the brain. This information relates to various modalities such as touch, temperature, itch and pain. The different modalities require a variety of subtypes of sensory neurons, tuned to detect and transmit specific stimuli. Each of these subtypes expresses a specific set of proteins to serve this highly specialized function and to control the cell type specific gene expression. This thesis explores the development and diversity of sensory neuronal subtypes in the dorsal root ganglion (DRG) of the mouse. In the five studies included in this thesis, we have investigated the roles of several genes in the development and function of sensory neurons. In Paper I, the focus is on a transcription factor, Cux2. We described that its expression is limited to large, early born neurons, which are mainly mechanosensitive, including a lineage of poorly characterized large TrkA+ neurons. We found no evidence that Cux2 would affect neuronal subtype specification, but instead we showed that it contributes to regulation of mechanosensation. Transcription factors themselves are closely regulated in order to be expressed at the right time and place in development. In Paper II we identified that FGF signaling from earlier-born neurons triggers the upregulation of the transcription factor Runx1 early in the development of the thermo-nociceptive lineage. Signaling by soluble factors is also involved in the late stages of maturation of neuronal identity, as we demonstrated in Paper IV for the Ret receptor. We reported that the loss of Ret expression caused a hypersensitivity to several sensory modalities and showed that Ret is necessary for the expression of a large number of ion channels and receptors. One of the Ret-regulated genes was the cold receptor TrpM8. In Paper III we showed that TrpM8 expression was confined to a small population of neurons lacking coexpression with most subtype markers. We also characterized the developmental expression of all members of the TrpM family in the DRG and showed that most of them were expressed with individual temporal patterns. Finally, in Paper V, we characterized the expression pattern of the enzyme Tyrosine hydroxylase (TH), the function of which is unknown in the DRG. TH is central in the catecholamine synthesis pathway, but whether or not that pathway is active in the DRG is uncertain. We showed that neurons expressing TH belong to the Ret+ population and that the expression of TH depends on Runx1 but not Ret. In summary, we have described a number of novel sensory neuron populations as well as genetic mechanisms governing development and diversification of specific populations. These results lead to a better understanding of the somatosensory system and hopefully in extension to better treatments for patients with somatosensory disturbances such as chronic pain conditions

Informe de investigacion 1997

Les activités du Département de recherches de la Gremial de Huleros ont été menées dans les domaines suivants : ressources génétiques, pratiques culturales, phytopathologie et exploitation de l'hévéa. L'acquisition de la plantation Santa Ana Mixpiya a permis d'établir un centre d'expérimentation. Les principaux résultats obtenus en 1997 dans les différentes stations sont présentés dans ce rapport annuel. Des jardins clonaux ont été établis pour l'évaluation du matériel génétique et pour la multiplication du matériel végétal. La collection de matériel génétique s'est également agrandie. L'évaluation des clones a été faite dans des champs à grande et à petite échelle. Les observations ont porté sur leurs caractéristiques morphologiques et leur sensibilité à #Microcyclus ulei#. Pour étudier l'exploitation de l'hévéa, différents systèmes de saignée avec ou sans stimulation ont été étudiés. En phytopathologie, on a expérimenté plusieurs traitements contre l'encoche sèche. Pour la production de plants greffés, on a évalué les caractéristiques agronomiques de semences d'origine différente, ainsi que leur sensibilité à #Microcyclus ulei# afin de les utiliser comme porte-greffes. Des essais de fertilisation (azote, phosphore et potassium) ont été menés sur plusieurs plantations. Tous les protocoles expérimentaux sont donnés en annexes