181 research outputs found
Evaluating the new ORDHIDEE-GM (Grassland Management) model to tropical area in Brazil.
The elevation on greenhouse gases (GEE) concentration is causing significant changes to the climate, with important economical and social consequences. In Brazil, cattle is under the spotlight both due the magnitude of GEE flow and because of its potential to mitigate emissions, particularly when considering the capacity of carbon sequestration in soils under pastures. On the other hand, cattle may suffer significant impacts with climate change. Forage species, animal breeds and productive systems, previously adapted, may be vulnerable under future scenarios, mainly due to thermal and hydric stress, resulting from adverse climate
Evaluating the new ORDHIDEE-GM (Grassland Management) model to tropical area in Brazil.
The elevation on greenhouse gases (GEE) concentration is causing significant changes to the climate, with important economical and social consequences. In Brazil, cattle is under the spotlight both due the magnitude of GEE flow and because of its potential to mitigate emissions, particularly when considering the capacity of carbon sequestration in soils under pastures. On the other hand, cattle may suffer significant impacts with climate change. Forage species, animal breeds and productive systems, previously adapted, may be vulnerable under future scenarios, mainly due to thermal and hydric stress, resulting from adverse climate
On War: The Dynamics of Vicious Civilizations
The dynamics of ``vicious'', continuously growing civilizations (domains),
which engage in ``war'' whenever two domains meet, is investigated. In the war
event, the smaller domain is annihilated, while the larger domain is reduced in
size by a fraction \e of the casualties of the loser. Here \e quantifies
the fairness of the war, with \e=1 corresponding to a fair war with equal
casualties on both side, and \e=0 corresponding to a completely unfair war
where the winner suffers no casualties. In the heterogeneous version of the
model, evolution begins from a specified initial distribution of domains, while
in the homogeneous system, there is a continuous and spatially uniform input of
point domains, in addition to the growth and warfare. For the heterogeneous
case, the rate equations are derived and solved, and comparisons with numerical
simulations are made. An exact solution is also derived for the case of equal
size domains in one dimension. The heterogeneous system is found to coarsen,
with the typical cluster size growing linearly in time and the number
density of domains decreases as . For the homogeneous system, two
different long-time behaviors arise as a function of \e. When 1/2<\e\leq 1
(relatively fair wars), a steady state arises which is characterized by
egalitarian competition between domains of comparable size. In the limiting
case of \e=1, rate equations which simultaneously account for the
distribution of domains and that of the intervening gaps are derived and
solved. The steady state is characterized by domains whose age is typically
much larger than their size. When 0\leq\e<1/2 (unfair wars), a few
``superpowers'' ultimately dominate. Simulations indicate that this coarsening
process is characterized by power-law temporal behavior, with non-universalComment: 43 pages, plain TeX, 12 figures included, gzipped and uuencode
Rectification and Phase Locking for Particles on Two Dimensional Periodic Substrates
We show that a novel rectification phenomena is possible for overdamped
particles interacting with a 2D periodic substrate and driven with a
longitudinal DC drive and a circular AC drive. As a function of DC amplitude,
the longitudinal velocity increases in a series of quantized steps with
transverse rectification occuring near these transitions. We present a simple
model that captures the quantization and rectification behaviors.Comment: 4 pages, 4 postscript figure
Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag
We study the electrophoretic separation of polyelectrolytes of varying
lengths by means of end-labeled free-solution electrophoresis (ELFSE). A
coarse-grained molecular dynamics simulation model, using full electrostatic
interactions and a mesoscopic Lattice Boltzmann fluid to account for
hydrodynamic interactions, is used to characterize the drag coefficients of
different label types: linear and branched polymeric labels, as well as
transiently bound micelles.
It is specifically shown that the label's drag coefficient is determined by
its hydrodynamic size, and that the drag per label monomer is largest for
linear labels. However, the addition of side chains to a linear label offers
the possibility to increase the hydrodynamic size, and therefore the label
efficiency, without having to increase the linear length of the label, thereby
simplifying synthesis. The third class of labels investigated, transiently
bound micelles, seems very promising for the usage in ELFSE, as they provide a
significant higher hydrodynamic drag than the other label types.
The results are compared to theoretical predictions, and we investigate how
the efficiency of the ELFSE method can be improved by using smartly designed
drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule
The global carbon budget 1959-2011
Accurate assessments of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the climate policy process, and project future climate change. Present-day analysis requires the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. Here we describe datasets and a methodology developed by the global carbon cycle science community to quantify all major components of the global carbon budget, including their uncertainties. We discuss changes compared to previous estimates, consistency within and among components, and methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics, while emissions from Land-Use Change (ELUC), including deforestation, are based on combined evidence from land cover change data, fire activity in regions undergoing deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. Finally, the global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms. For the last decade available (2002–2011), EFF was 8.3 ± 0.4 PgC yr−1, ELUC 1.0 ± 0.5 PgC yr−1, GATM 4.3 ± 0.1PgC yr−1, SOCEAN 2.5 ± 0.5 PgC yr−1, and SLAND 2.6 ± 0.8 PgC yr−1. For year 2011 alone, EFF was 9.5 ± 0.5 PgC yr−1, 3.0 percent above 2010, reflecting a continued trend in these emissions; ELUC was 0.9 ± 0.5 PgC yr−1, approximately constant throughout the decade; GATM was 3.6 ± 0.2 PgC yr−1, SOCEAN was 2.7 ± 0.5 PgC yr−1, and SLAND was 4.1 ± 0.9 PgC yr−1. GATM was low in 2011 compared to the 2002–2011 average because of a high uptake by the land probably in response to natural climate variability associated to La Niña conditions in the Pacific Ocean. The global atmospheric CO2 concentration reached 391.31 ± 0.13 ppm at the end of year 2011. We estimate that EFF will have increased by 2.6% (1.9–3.5%) in 2012 based on projections of gross world product and recent changes in the carbon intensity of the economy. All uncertainties are reported as ±1 sigma (68% confidence assuming Gaussian error distributions that the real value lies within the given interval), reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. This paper is intended to provide a baseline to keep track of annual carbon budgets in the future
Direct and seasonal legacy effects of the 2018 heat wave and drought on European ecosystem productivity
In summer 2018, central and northern Europe were stricken by extreme drought and heat (DH2018). The DH2018 differed from previous events in being preceded by extreme spring warming and brightening, but moderate rainfall deficits, yet registering the fastest transition between wet winter conditions and extreme summer drought. Using 11 vegetation models, we show that spring conditions promoted increased vegetation growth, which, in turn, contributed to fast soil moisture depletion, amplifying the summer drought. We find regional asymmetries in summer ecosystem carbon fluxes: increased (reduced) sink in the northern (southern) areas affected by drought. These asymmetries can be explained by distinct legacy effects of spring growth and of water-use efficiency dynamics mediated by vegetation composition, rather than by distinct ecosystem responses to summer heat/drought. The asymmetries in carbon and water exchanges during spring and summer 2018 suggest that future land-management strategies could influence patterns of summer heat waves and droughts under long-term warming
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