Coupled Groups of g-Modes in a Sun with Mixed Core

Groups of linear g-modes can sum to create long-lived nonlinear oscillations in small "hot volumes" very deep in the Sun that help drive the modes. In these volumes (dimensions -10 Mm), the time average rate of He-3 burning doubles as temperature fluctuations exceed 10% and rises by an order of magnitude for fluctuations of 25%. To be consistent with locally large motions, we impose a mixed shell on an otherwise standard solar model before computing g-mode solutions. Mixing in the assumed shell r = (0.10+/-0.03) R(sub sun) is rapid ( 3. A formalism is presented for summing the g-modes and estimating growth rates under the approximation that modes are strictly linear except in a hot volume which holds only a few percent of mode kinetic energy. Finally over the range 2 less than or equal to l less than or equal to 30, we summed all zonal harmonics, m, for a given l and computed the relative angular orientations that would release the most nuclear energy. This should be close to the physically preferred angular state of such a family and a few examples were displayed

Reurbanisation in Postsocialist Europe - A Comparative View of Eastern Germany, Poland, and the Czech Republic

Since the 1990s, reurbanisation has become an increasingly frequent trajectory for urban development. Many formerly shrinking cities have been able to stabilise their population or even see new growth. Especially prominent in regions like Germany and the UK, but also observed across the whole continent, a lively debate on reurbanisation has developed as a reality of today’s, and a potential trajectory for tomorrow’s, cities in Europe. Postsocialist Europe has not so far been central in the reurbanisation debate, either empirically or theoretically. Subsequently, the postsocialist experience is missing in the discourse and the existing body of evidence. There is, however, some evidence that Czech and Polish cities are also seeing signs of new inner-city growth and a trend towards core city stabilisation. Against this background, the paper scrutinises the issues of reurbanisation and new growth after the shrinking of postsocialist cities. The paper uses the approach of a contrastive comparison between cities in eastern Germany, where reurbanisation has developed as the predominant trajectory for many large cities, and for cities in Poland and the Czech Republic, where this trend is considerably less prominent. It analyses the development of reurbanisation in these cities and their urban regions over the last few decades, its characteristics and the determinants triggering or impeding it. The paper includes data on a national scale as well as from relevant case studies of cities and their urban regions. It argues, among other things, that there is no "postsocialist model" with regard to influencing factors for reurbanisation. Eastern Germany, due to its specific postsocialist situation and transformation trajectory, can be viewed as an "outlier" or "hybrid" which exhibits characteristics typical of postsocialist and western welfare contexts and which is seeing especially dynamic reurbanisation after a phase of extreme shrinkage. Although there are clear signs of inner-city reurbanisation in Polish and Czech cities as well, it seems relatively unlikely that this process will reach the same high levels as in East German cities within the coming years

Reurbanisation in Postsocialist Europe – A Comparative View of Eastern Germany, Poland, and the Czech Republic

Since the 1990s, reurbanisation has become an increasingly frequent trajectory for urban development. Many formerly shrinking cities have been able to stabilise their population or even see new growth. Especially prominent in regions like Germany and the UK, but also observed across the whole continent, a lively debate on reurbanisation has developed as a reality of today’s, and a potential trajectory for tomorrow’s, cities in Europe.Postsocialist Europe has not so far been central in the reurbanisation debate, either empirically or theoretically. Subsequently, the postsocialist experience is missing in the discourse and the existing body of evidence. There is, however, some evidence that Czech and Polish cities are also seeing signs of new inner-city growth and a trend towards core city stabilisation.Against this background, the paper scrutinises the issues of reurbanisation and new growth after the shrinking of postsocialist cities. The paper uses the approach of a contrastive comparison between cities in eastern Germany, where reurbanisation has developed as the predominant trajectory for many large cities, and for cities in Poland and the Czech Republic, where this trend is considerably less prominent. It analyses the development of reurbanisation in these cities and their urban regions over the last few decades, its characteristics and the determinants triggering or impeding it. The paper includes data on a national scale as well as from relevant case studies of cities and their urban regions.It argues, among other things, that there is no “postsocialist model” with regard to influencing factors for reurbanisation. Eastern Germany, due to its specific postsocialist situation and transformation trajectory, can be viewed as an “outlier” or “hybrid” which exhibits characteristics typical of postsocialist and western welfare contexts and which is seeing especially dynamic reurbanisation after a phase of extreme shrinkage. Although there are clear signs of inner-city reurbanisation in Polish and Czech cities as well, it seems relatively unlikely that this process will reach the same high levels as in East German cities within the coming years. * This article belongs to a special issue on reurbanisation

Increased uncertainty in projections of precipitation and evaporation due to wet‐get‐wetter/dry‐get‐drier biases

The research was supported by the Israel Science Foundation Grant 1022/21.A key implication of the well known wet‐get‐wetter/dry‐get‐drier (WGW) scaling is that model biases in the representation of precipitation and evaporation in the present climate lead to spurious projected changes under global warming. Here we estimate the extent of such spurious changes in projections by 60 models participating in phases 5 and 6 of the Coupled Model Intercomparison Project. Utilizing known thermodynamic constraints on evaporation, we show that the WGW scaling can be applied to precipitation and evaporation separately (specific WGW scaling), which we use to correct for spurious projected changes in precipitation and evaporation over tropical oceans. The spurious changes in precipitation can be of comparable amplitude to projected changes, but are generally small for evaporation. The spurious changes may increase the uncertainty in projections of tropical precipitation and evaporation by up to 30% and 15% respectively.Publisher PDFPeer reviewe

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Summer Precipitation Predicts Spatial Distributions of Semiaquatic Mammals

Citation: Ahlers, A. A., Cotner, L. A., Wolff, P. J., Mitchell, M. A., Heske, E. J., & Schooley, R. L. (2015). Summer Precipitation Predicts Spatial Distributions of Semiaquatic Mammals. Plos One, 10(8), 14. doi:10.1371/journal.pone.0135036Climate change is predicted to increase the frequency of droughts and intensity of seasonal precipitation in many regions. Semiaquatic mammals should be vulnerable to this increased variability in precipitation, especially in human-modified landscapes where dispersal to suitable habitat or temporary refugia may be limited. Using six years of presence-absence data (2007-2012) spanning years of record-breaking drought and flood conditions, we evaluated regional occupancy dynamics of American mink (Neovison vison) and muskrats (Ondatra zibethicus) in a highly altered agroecosystem in Illinois, USA. We used noninvasive sign surveys and a multiseason occupancy modeling approach to estimate annual occupancy rates for both species and related these rates to summer precipitation. We also tracked radiomarked individuals to assess mortality risk for both species when moving in terrestrial areas. Annual model-averaged estimates of occupancy for mink and muskrat were correlated positively to summer precipitation. Mink and muskrats were widespread during a year (2008) with above-average precipitation. However, estimates of site occupancy declined substantially for mink (0.56) and especially muskrats (0.09) during the severe drought of 2012. Mink are generalist predators that probably use terrestrial habitat during droughts. However, mink had substantially greater risk of mortality away from streams. In comparison, muskrats are more restricted to aquatic habitats and likely suffered high mortality during the drought. Our patterns are striking, but a more mechanistic understanding is needed of how semiaquatic species in human-modified ecosystems will respond ecologically in situ to extreme weather events predicted by climate-change models

Discovery of a Companion Candidate in the HD169142 Transition Disk and the Possibility of Multiple Planet Formation

We present L' and J-band high-contrast observations of HD169142, obtained with the VLT/NACO AGPM vector vortex coronagraph and the Gemini Planet Imager, respectively. A source located at 0".156+/-0".032 north of the host star (PA=7.4+/-11.3 degrees) appears in the final reduced L' image. At the distance of the star (~145 pc), this angular separation corresponds to a physical separation of 22.7+/-4.7 AU, locating the source within the recently resolved inner cavity of the transition disk. The source has a brightness of L'=12.2+/-0.5 mag, whereas it is not detected in the J band (J>13.8 mag). If its L' brightness arose solely from the photosphere of a companion and given the J-L' color constraints, it would correspond to a 28-32 MJupiter object at the age of the star, according to the COND models. Ongoing accretion activity of the star suggests, however, that gas is left in the inner disk cavity from which the companion could also be accreting. In this case the object could be lower in mass and its luminosity enhanced by the accretion process and by a circumplanetary disk. A lower mass object is more consistent with the observed cavity width. Finally, the observations enable us to place an upper limit on the L'-band flux of a second companion candidate orbiting in the disk annular gap at ~50 AU, as suggested by millimeter observations. If the second companion is also confirmed, HD169142 might be forming a planetary system, with at least two companions opening gaps and possibly interacting with each other.Comment: Accepted to ApJL, see also Biller et al. 201

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