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Träfflista för sökning "WFRF:(Marten A) ;srt2:(2005-2009)"

Sökning: WFRF:(Marten A) > (2005-2009)

  • Resultat 1-8 av 8
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2.
  • Abrikosov, Igor, et al. (författare)
  • Magnetism in systems with reduced dimensionality and chemical disorder : the local environment effects
  • 2006
  • Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier. - 0304-8853 .- 1873-4766. ; 300:1, s. 211-215
  • Tidskriftsartikel (refereegranskat)abstract
    • We study influence of the local chemical environment, the so-called local environment effects, on the electronic structure and properties of magnetic systems with reduced dimensionality and chemical disorder, and show that they play a crucial role in a vicinity of magnetic instability. As a model, we consider Fe–Ni Invar. We present results obtained from ab initio calculations of the electronic structure, magnetic moments, and exchange interactions in random fcc Fe–Ni alloy, for a single monolayer alloy film on a Cu (0 0 1) substrate as well as in the bulk. We analyze the difference between the film and the bulk magnetization, which is found to be most pronounced for dilute alloys. We also analyze a sensitivity of the individual magnetic moments and effective exchange parameters to the local chemical environment of the atoms.
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3.
  • Alling, Björn, 1980-, et al. (författare)
  • Comparison of thermodynamic properties of cubic Cr 1-x Al x N and Ti 1-x Al x N from first-principles calculations
  • 2007
  • Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 102:044314
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to investigate the stability of the cubic phase of Cr1−xAlxN at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti1−xAlxN and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr- and Ti-containing systems. Cr1−xAlxN turns out to be more stable against spinodal decomposition than Ti1−xAlxN, especially for AlN-rich samples which are of interest in cutting tools applications.
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4.
  • Hjernquist, Marten B., et al. (författare)
  • Sex allocation in response to local resource competition over breeding territories
  • 2009
  • Ingår i: Behavioral Ecology. - 1045-2249 .- 1465-7279. ; 20:2, s. 335-339
  • Tidskriftsartikel (refereegranskat)abstract
    • Sex allocation according to local resource competition suggests that investment and offspring sex ratio should be biased toward the dispersing sex to limit the competition among the natal philopatric sex. Conversely, when competition over resources is low, parents should allocate more resources toward the philopatric sex. In this study, this reciprocal scenario of sex allocation is tested. More specifically, the effect of breeding territory availability on primary sex ratio is studied in the collared flycatcher, a migratory passerine bird, where males are the natal philopatric sex. As predicted, primary sex ratios were biased toward males in areas where available territories were abundant (estimated from population growth). No relationship between sex ratio adjustment and adult phenotypes as well as date of first egg was found. We discuss potential explanation for the male-biased broods in areas with many vacant territories and low levels of competition. We suggest that sex ratio adjustment in relation to breeding territory quality and availability could be relatively common in birds.
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7.
  • Rockström, Johan, et al. (författare)
  • A safe operating space for humanity
  • 2009
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 461:7263, s. 472-475
  • Tidskriftsartikel (refereegranskat)
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8.
  • Rockström, Johan, et al. (författare)
  • Planetary Boundaries : Exploring the Safe Operating Space for Humanity
  • 2009
  • Ingår i: Ecology & Society. - 1708-3087. ; 14:2, s. 32-
  • Tidskriftsartikel (refereegranskat)abstract
    • Anthropogenic pressures on the Earth System have reached a scale where abrupt global environmental change can no longer be excluded. We propose a new approach to global sustainability in which we define planetary boundaries within which we expect that humanity can operate safely. Transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental- to planetary-scale systems. We have identified nine planetary boundaries and, drawing upon current scientific understanding, we propose quantifications for seven of them. These seven are climate change (CO2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m(-2) in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite >= 80% of pre-industrial levels); stratospheric ozone (<5% reduction in O-3 concentration from pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N-2 to 35 Tg N yr(-1)) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (<4000 km(3) yr(-1) of consumptive use of runoff resources); land system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for which we have not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading. We estimate that humanity has already transgressed three planetary boundaries: for climate change, rate of biodiversity loss, and changes to the global nitrogen cycle. Planetary boundaries are interdependent, because transgressing one may both shift the position of other boundaries or cause them to be transgressed. The social impacts of transgressing boundaries will be a function of the social-ecological resilience of the affected societies. Our proposed boundaries are rough, first estimates only, surrounded by large uncertainties and knowledge gaps. Filling these gaps will require major advancements in Earth System and resilience science. The proposed concept of "planetary boundaries" lays the groundwork for shifting our approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externalities, toward the estimation of the safe space for human development. Planetary boundaries define, as it were, the boundaries of the "planetary playing field" for humanity if we want to be sure of avoiding major human-induced environmental change on a global scale.
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