4,747 research outputs found
Environmental Superstatistics
A thermodynamic device placed outdoors, or a local ecosystem, is subject to a
variety of different temperatures given by short-tem (daily) and long-term
(seasonal) variations. In the long term a superstatistical description makes
sense, with a suitable distribution function f(beta) of inverse temperature
beta over which ordinary statistical mechanics is averaged. We show that
f(beta) is very different at different geographic locations, and typically
exhibits a double-peak structure for long-term data. For some of our data sets
we also find a systematic drift due to global warming. For a simple
superstatistical model system we show that the response to global warming is
stronger if temperature fluctuations are taken into account.Comment: 37 figures. Significantly extended version, to appear in Physica A.
Added new material in section 6 quantifying the stronger response to global
warming if temperature fluctuations are taken into account. Concluding
section 7 and several new references adde
Extreme event statistics of daily rainfall: Dynamical systems approach
We analyse the probability densities of daily rainfall amounts at a variety
of locations on the Earth. The observed distributions of the amount of rainfall
fit well to a q-exponential distribution with exponent q close to q=1.3. We
discuss possible reasons for the emergence of this power law. On the contrary,
the waiting time distribution between rainy days is observed to follow a
near-exponential distribution. A careful investigation shows that a
q-exponential with q=1.05 yields actually the best fit of the data. A Poisson
process where the rate fluctuates slightly in a superstatistical way is
discussed as a possible model for this. We discuss the extreme value statistics
for extreme daily rainfall, which can potentially lead to flooding. This is
described by Frechet distributions as the corresponding distributions of the
amount of daily rainfall decay with a power law. On the other hand, looking at
extreme event statistics of waiting times between rainy days (leading to
droughts for very long dry periods) we obtain from the observed
near-exponential decay of waiting times an extreme event statistics close to
Gumbel distributions. We discuss superstatistical dynamical systems as simple
models in this context.Comment: 10 pages, 15 figures. Replaced by final version published in J.Phys.
Entropies for severely contracted configuration space
We demonstrate that dual entropy expressions of the Tsallis type apply
naturally to statistical-mechanical systems that experience an exceptional
contraction of their configuration space. The entropic index
describes the contraction process, while the dual index defines the contraction dimension at which extensivity is
restored. We study this circumstance along the three routes to chaos in
low-dimensional nonlinear maps where the attractors at the transitions, between
regular and chaotic behavior, drive phase-space contraction for ensembles of
trajectories. We illustrate this circumstance for properties of systems that
find descriptions in terms of nonlinear maps. These are size-rank functions,
urbanization and similar processes, and settings where frequency locking takes
place
Incidence of -statistics in rank distributions
We show that size-rank distributions with power-law decay (often only over a
limited extent) observed in a vast number of instances in a widespread family
of systems obey Tsallis statistics. The theoretical framework for these
distributions is analogous to that of a nonlinear iterated map near a tangent
bifurcation for which the Lyapunov exponent is negligible or vanishes. The
relevant statistical-mechanical expressions associated with these distributions
are derived from a maximum entropy principle with the use of two different
constraints, and the resulting duality of entropy indexes is seen to portray
physically relevant information. While the value of the index fixes
the distribution's power-law exponent, that for the dual index
ensures the extensivity of the deformed entropy.Comment: Santa Fe Institute working paper:
http://www.santafe.edu/media/workingpapers/14-07-024.pdf. see:
http://www.pnas.org/content/early/2014/09/03/1412093111.full.pdf+htm
Distribution of some elements in Veronica scutellata L. from Bolu,Turkey: soil-plant interactions
Veronica scutellata L. occurs in moist and wet habitats, such as ponds, marshes and other wetlands. This study was conducted on this species to examine its mineral element uptake status in terms of interactions between soil and plant. Experimental materials were taken from the Southern coast of Black Sea at coordinates 40º36’N and 31º16’E at an altitude of 1400 m above sea level from Bolu – Turkey; using standard methods and plant (root, stem and leaf parts) and soil mineral element measurements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, Ni and Zn) were done. During the study, ICP-OES was employed for the measurement of mineral elements. It was observed that considerable amounts of B, Ca, K, Mg, Mn, Na and Zn are accumulated by the plant
Fewer but poorer: Benevolent partiality in prosocial preferences
A prosocial action typically provides a more sizable benefit when directed at those who have less as opposed to those who have more. However, not all prosocial acts have a direct bearing on socioeconomic disadvantage, nor does disadvantage necessarily imply a greater need for the prosocial outcome. Of interest here, welfare impact may depend on the number of beneficiaries but not on their socioeconomic status. Across four preregistered studies of life-saving decisions, we demonstrate that when allocating resources, many people are benevolently partial. That is, they choose to help the disadvantaged even when this transparently implies sacrificing lives. We suggest that people construct prosocial aid as an opportunity to correct morally aversive inequalities, thusmaking relativelymore disadvantaged recipients amore justifiable target of help. Benevolent partiality is reduced when people reflect beforehand on what aspects they will prioritize in their donation decision
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