2,616 research outputs found

    Are the Earth and the Moon compositionally alike? Inferences on lunar composition and implications for lunar origin and evolution from geophysical modeling

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    The main objective of the present study is to discuss in detail the results obtained from an inversion of the Apollo lunar seismic data set, lunar mass, and moment of inertia. We inverted directly for lunar chemical composition and temperature using the model system CaO-FeO-MgO-Al2O3-SiO2. Using Gibbs free energy minimization, stable mineral phases at the temperatures and pressures of interest, their modes and physical properties are calculated. We determine the compositional range of the oxide elements, thermal state, Mg#, mineralogy and physical structure of the lunar interior, as well as constraining core size and density. The results indicate a lunar mantle mineralogy that is dominated by olivine and orthopyroxene ( 80 vol%), with the remainder being composed of clinopyroxene and an aluminous phase (plagioclase, spinel, and garnet present in the depth ranges 0–150 km, 150–200 km, and >200 km, respectively). This model is broadly consistent with constraints on mantle mineralogy derived from the experimental and observational study of the phase lationships and trace element compositions of lunar mare basalts and picritic glasses. In particular, by melting a typical model mantle composition using the pMELTS algorithm, we found that a range of batch melts generated from these models have features in common with low Ti mare basalts and picritic glasses. Our results also indicate a bulk lunar composition and Mg# different to that of the Earth’s upper mantle, represented by the pyrolite composition. This difference is reflected in a lower bulk lunar Mg# ( 0.83). Results also indicate a small iron-like core with a radius around 340 km.The Carlsberg Foundation, NER

    Joint inversion of seismic and gravity data for lunar composition and thermal state

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    We invert the Apollo lunar seismic data set, together with lunar mass and moment of inertia, directly for the chemical composition and thermal state of the Moon. The lunar mantle and crust are modelled in the chemical system CaO-FeO-MgO-Al2O3-SiO2. The stable minerals, their seismic properties, and the bulk density are computed by Gibbs free energy minimization. Voigt-Reuss-Hill averaging is then used to compute seismic-wave velocity profiles, from which traveltimes are estimated, while mass and moment of inertia are obtained by integration of the density profile. Given this scheme, the data are jointly inverted using a Markov chain Monte Carlo algorithm, from which a range of compositions and temperatures fitting data within uncertainties are obtained. The analysis constrains the range of compositions, thermal states, mineralogy and physical structure of the lunar interior that are consistent with data. Additionally, the analysis provides estimates for the size and density of the lunar core. The inferred lunar compositions have lower Mg#s (∌83) than the Earth's mantle (∌89), suggesting that the Moon was derived from material other than the Earth's mantle. This supports giant impact simulations of lunar origin that show that more than 80 per cent of the material making up the Moon is derived from the impacto

    Quantum Non-Equilibrium Steady States Induced by Repeated Interactions

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    We study the steady state of a finite XX chain coupled at its boundaries to quantum reservoirs made of free spins that interact one after the other with the chain. The two-point correlations are calculated exactly and it is shown that the steady state is completely characterized by the magnetization profile and the associated current. Except at the boundary sites, the magnetization is given by the average of the reservoirs' magnetizations. The steady state current, proportional to the difference in the reservoirs' magnetizations, shows a non-monotonous behavior with respect to the system-reservoir coupling strength, with an optimal current state for a finite value of the coupling. Moreover, we show that the steady state can be described by a generalized Gibbs state.Comment: to appear in Phys. Rev. Let

    Charged Higgs phenomenology in the flipped two Higgs doublet model

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    We study the phenomenology of the charged Higgs boson in the "flipped" two Higgs doublet model, in which one doublet gives mass to up-type quarks and charged leptons and the other gives mass to down-type quarks. We present the charged Higgs branching ratios and summarize the indirect constraints. We extrapolate existing LEP searches for H+H- and Tevatron searches for t tbar with t --> H+ b into the flipped model and extract constraints on MH+ and the parameter tan(beta). We finish by reviewing existing LHC charged Higgs searches and suggest that the LHC reach in this model could be extended for charged Higgs masses below the tb threshold by considering t tbar with t --> H+ b and H+ --> q qbar, as has been used in Tevatron searches.Comment: 23 pages, 7 figures. V2: added refs on H+W- associated productio

    Comparability of surrogate and self-reported information on melanoma risk factors.

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    Surrogate reports by patients about their relatives, and vice versa, are potentially of great use in studies of the genetic and environmental causes of the familial aggregation of cancer. To assess the quality of such information in a family study of melanoma aetiology in Queensland, Australia, the authors compared surrogate reports with self-reports of standard melanoma risk factors obtained by mailed self-administered questionnaire. There was moderate agreement between surrogate reports provided by the cases and relatives' self-reports for questions on ability to tan (polychoric correlation coefficient (pc) = 0.60), skin colour (pc = 0.57), average propensity to burn (pc = 0.56), and hair colour at age 21 (kappa coefficient = 0.55), although relatives in the extreme risk factor categories were misclassified by surrogates at least half of the time. Agreement was lower for questions on degree of moliness (pc = 0.45), tendency to acute sunburn (pc = 0.42), and number of episodes of painful sunburn (pc = 0.23). The quality of relatives' surrogate reports about cases was similar to that of cases' surrogate reports about relatives. Cases who reported a family history of melanoma provided better surrogate information than did cases who indicated no family history, and female cases provided better surrogate reports than did males. Cases were better able to report for their parents and children than for their siblings. The authors conclude that when the use of surrogate reports of melanoma risk factors is unavoidable, results should be interpreted cautiously in the light of potentially high rates of misclassification. In particular, surrogate reports appear to be a comparatively poor measure of self-assessment of number of moles, the strongest known phenotypic indicator of melanoma risk, and may bias comparisons between families with and without a history of melanoma

    Charged particle composition in the inner heliosphere during the rise to maximum of Solar Cycle 23

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    Flux distributions and abundances relative to oxygen of interplanetary ions (Z>1)(Z>1) are statistically studied and compared for measurements made at 1 and at ∌5 AU on the ACE and the Ulysses spacecraft near the ecliptic plane. Over the nearly two year interval studied, the distributions of the relative abundances and the fluxes of particles at the two locations are found to be approximately log normal. The statistical distributions of the relative abundances are found to be similar at the two helioradii. On a statistical basis, the fluxes at Ulysses times the distance of the measurements appear to be proportional to the fluxes at ACE. This radial dependence of the fluxes is consistent with the interpretation that, statistically, the ion parallel diffusion coefficient is large. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87340/2/169_1.pd

    Cognition as Embodied Morphological Computation

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    Cognitive science is considered to be the study of mind (consciousness and thought) and intelligence in humans. Under such definition variety of unsolved/unsolvable problems appear. This article argues for a broad understanding of cognition based on empirical results from i.a. natural sciences, self-organization, artificial intelligence and artificial life, network science and neuroscience, that apart from the high level mental activities in humans, includes sub-symbolic and sub-conscious processes, such as emotions, recognizes cognition in other living beings as well as extended and distributed/social cognition. The new idea of cognition as complex multiscale phenomenon evolved in living organisms based on bodily structures that process information, linking cognitivists and EEEE (embodied, embedded, enactive, extended) cognition approaches with the idea of morphological computation (info-computational self-organisation) in cognizing agents, emerging in evolution through interactions of a (living/cognizing) agent with the environment
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