1,051 research outputs found
Interactively modelling land profitability to estimate European agricultural and forest land use under future scenarios of climate, socio-economics and adaptation
Studies of climate change impacts on agricultural land use generally consider sets of climates combined with fixed socio-economic scenarios, making it impossible to compare the impact of specific factors within these scenario sets. Analysis of the impact of specific scenario factors is extremely difficult due to prohibitively long run-times of the complex models. This study produces and combines metamodels of crop and forest yields and farm profit, derived from previously developed very complex models, to enable prediction of European land use under any set of climate and socio-economic data. Land use is predicted based on the profitability of the alternatives on every soil within every 10' grid across the EU. A clustering procedure reduces 23,871 grids with 20+ soils per grid to 6,714 clusters of common soil and climate. Combined these reduce runtime 100 thousand-fold. Profit thresholds define land as intensive agriculture (arable or grassland), extensive agriculture or managed forest, or finally unmanaged forest or abandoned land. The demand for food as a function of population, imports, food preferences and bioenergy, is a production constraint, as is irrigation water available. An iteration adjusts prices to meet these constraints. A range of measures are derived at 10' grid-level such as diversity as well as overall EU production. There are many ways to utilise this ability to do rapidWhat-If analysis of both impact and adaptations. The paper illustrates using two of the 5 different GCMs (CSMK3, HADGEM with contrasting precipitation and temperature) and two of the 4 different socio-economic scenarios ("We are the world", "Should I stay or should I go" which have contrasting demands for land), exploring these using two of the 13 scenario parameters (crop breeding for yield and population) . In the first scenario, population can be increased by a large amount showing that food security is far from vulnerable. In the second scenario increasing crop yield shows that it improves the food security problem
Long-term variability of drought indices in the Czech Lands and effects of external forcings and large-scale climate variability modes
While a considerable number of records document the temporal variability of
droughts for central Europe, the understanding of its underlying causes remains
limited. In this contribution, time series of three drought indices (Standardized Precipitation Index –
SPI; Standardized Precipitation Evapotranspiration Index – SPEI; Palmer Drought Severity Index – PDSI) are analyzed with regard to mid- to long-term drought variability
in the Czech Lands and its potential links to external forcings and internal
climate variability modes over the 1501–2006 period. Employing instrumental
and proxy-based data characterizing the external climate forcings (solar and
volcanic activity, greenhouse gases) in parallel with series representing the
activity of selected climate variability modes (El Niño–Southern
Oscillation – ENSO; Atlantic Multidecadal Oscillation – AMO; Pacific
Decadal Oscillation – PDO; North Atlantic Oscillation – NAO), regression
and wavelet analyses were deployed to identify and quantify the temporal
variability patterns of drought indices and similarity between individual
signals. Aside from a strong connection to the NAO, temperatures in the AMO
and (particularly) PDO regions were disclosed as one of the possible drivers
of inter-decadal variability in the Czech drought regime. Colder and wetter
episodes were found to coincide with increased volcanic activity, especially
in summer, while no clear signature of solar activity was found. In addition
to identification of the links themselves, their temporal stability and
structure of their shared periodicities were investigated. The oscillations
at periods of approximately 60–100 years were found to be potentially
relevant in establishing the teleconnections affecting the long-term
variability of central European droughts.</p
The Grassmannian and the Twistor String: Connecting All Trees in N=4 SYM
We present a new, explicit formula for all tree-level amplitudes in N=4 super
Yang-Mills. The formula is written as a certain contour integral of the
connected prescription of Witten's twistor string, expressed in link variables.
A very simple deformation of the integrand gives directly the Grassmannian
integrand proposed by Arkani-Hamed et al. together with the explicit contour of
integration. The integral is derived by iteratively adding particles to the
Grassmannian integral, one particle at a time, and makes manifest both parity
and soft limits. The formula is shown to be related to those given by Dolan and
Goddard, and generalizes the results of earlier work for NMHV and N^2MHV to all
N^(k-2)MHV tree amplitudes in N=4 super Yang-Mills.Comment: 26 page
Saturation properties of nuclear matter in a relativistic mean field model constrained by the quark dynamics
We have built an effective Walecka-type hadronic Lagrangian in which the
hadron masses and the density dependence of the coupling constants are deduced
from the quark dynamics using a Nambu-Jona-Lasinio model. In order to stabilize
nuclear matter an eight-quark term has been included. The parameters of this
Nambu-Jona-Lasinio model have been determined using the meson properties in the
vacuum but also in the medium through the omega meson mass in nuclei measured
by the TAPS collaboration. Realistic properties of nuclear matter have been
obtained.Comment: 14 pages, 2 figures, submitted to Nuclear Physics
The kinetic studies of the solvent-promoted aggregation of a steroid-porphyrin derivative
The study of the aggregation of a steroid-functionalised porphyrin derivative shows the
formation of chiral suprastuctures. Kinetic studies indicate that the mechanism of the aggregation strongly
depends on both the nature of the media and on the concentration of the tetrapyrrolic macrocycle
Dileptons and Medium Effects in Heavy-Ion Collisions
We discuss the status of calculating in-medium modifications of vector-meson
spectral functions in hot and dense matter, their application to dilepton
spectra in ultrarelativistic heavy-ion collisions, and possible relations to
chiral symmetry restoration. We emphasize the importance of constraining
in-medium spectral functions by empirical information from scattering data, QCD
sum rules, and lattice QCD. This is a mandatory prerequisite to arrive at
reliable predictions for low-mass dileptons in heavy-ion collisions.Comment: 8 pages latex, 15 figure
Extreme droughts and human responses to them: the Czech Lands in the pre-instrumental period
The Czech Lands are particularly rich in documentary sources that help
elucidate droughts in the pre-instrumental period (12th–18th centuries),
together with descriptions of human responses to them. Although droughts
appear less frequently before 1501, the documentary evidence has enabled the
creation of a series of seasonal and summer half-year drought indices
(Standardized Precipitation Index, SPI; Standardized Precipitation
Evapotranspiration Index, SPEI; Z index) for the Czech Lands for the
1501–2017 period. Based on the calculation of return period for series of
drought indices, extreme droughts were selected for inclusion herein if all
three indices indicated a return period of ≥20 years. For further
analysis, only those from the pre-instrumental period (before 1804) were
used. The extreme droughts selected are characterized by significantly lower
values of drought indices, higher temperatures and lower precipitation totals
compared to other years. The sea-level pressure patterns typically associated
with extreme droughts include significantly higher pressure over Europe and
significantly lower pressure over parts of the Atlantic Ocean. Extreme
droughts with a return period ≥ 50 years are described in detail on the
basis of Czech documentary evidence. A number of selected extreme droughts
are reflected in other central European reconstructions derived from
documentary data or tree rings. Impacts on social life and responses to
extreme droughts are summarized; analysis of fluctuations in grain prices
with respect to drought receives particular attention. Finally, extreme
droughts from the pre-instrumental and instrumental periods are discussed.</p
Early modern human settlement of Europe north of the Alps occurred 43,500 years ago in a cold steppe-type environment.
The first settlement of Europe by modern humans is thought to have occurred between 50,000 and 40,000 calendar years ago (cal B.P.). In Europe, modern human remains of this time period are scarce and often are not associated with archaeology or originate from old excavations with no contextual information. Hence, the behavior of the first modern humans in Europe is still unknown. Aurignacian assemblages--demonstrably made by modern humans--are commonly used as proxies for the presence of fully behaviorally and anatomically modern humans. The site of Willendorf II (Austria) is well known for its Early Upper Paleolithic horizons, which are among the oldest in Europe. However, their age and attribution to the Aurignacian remain an issue of debate. Here, we show that archaeological horizon 3 (AH 3) consists of faunal remains and Early Aurignacian lithic artifacts. By using stratigraphic, paleoenvironmental, and chronological data, AH 3 is ascribed to the onset of Greenland Interstadial 11, around 43,500 cal B.P., and thus is older than any other Aurignacian assemblage. Furthermore, the AH 3 assemblage overlaps with the latest directly radiocarbon-dated Neanderthal remains, suggesting that Neanderthal and modern human presence overlapped in Europe for some millennia, possibly at rather close geographical range. Most importantly, for the first time to our knowledge, we have a high-resolution environmental context for an Early Aurignacian site in Central Europe, demonstrating an early appearance of behaviorally modern humans in a medium-cold steppe-type environment with some boreal trees along valleys around 43,500 cal B.P.We thank the Leakey Foundation (2006–2012), Max Planck Society (2006–2012), University of Vienna (2006–2011), Hugo Obermaier Society (2006), Federal Office for Scientific Affairs of the State of Belgium (projects Sc-004, Sc-09, MO/36/021), and the Hochschuljubiläumsfonds of the City of Vienna (2007) for funding our research. We further acknowledge the support of the Department of Prehistory (Natural History Museum, Vienna, Austria; W. Antl-Weiser), Marktgemeinde Aggsbach (H. Gerstbauer), Museumsverein Willendorf (K. Kappelmüller), and the Satzl and Perzl families.This is the accepted manuscript version of the article. The final version is available from PNAS at http://www.pnas.org/content/early/2014/09/16/1412201111.abstract
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