1,599 research outputs found
Collisional invariants for the phonon Boltzmann equation
For the phonon Boltzmann equation with only pair collisions we characterize
the set of all collisional invariants under some mild conditions on the
dispersion relation
Approach to equilibrium for the phonon Boltzmann equation
We study the asymptotics of solutions of the Boltzmann equation describing
the kinetic limit of a lattice of classical interacting anharmonic oscillators.
We prove that, if the initial condition is a small perturbation of an
equilibrium state, and vanishes at infinity, the dynamics tends diffusively to
equilibrium. The solution is the sum of a local equilibrium state, associated
to conserved quantities that diffuse to zero, and fast variables that are
slaved to the slow ones. This slaving implies the Fourier law, which relates
the induced currents to the gradients of the conserved quantities.Comment: 23 page
Phosphorus and nitrogen cycling in forest soils depending on long-term nitrogen inputs
Foliar phosphorus (P) contents have been decreasing in a range of temperate forests in Europe and North America during the last decades, and one reason for this might be atmospheric nitrogen (N) deposition (1,2,3). Therefore, we studied the effect of N inputs on P and N cycling in long-term N fertilization experiments in temperate forests. The aim of the study was to test how increased N inputs affect P and N cycling in forest soils. We sampled the organic layer of three N fertilization experiments in the USA (Harvard Forest, Cary Institute and Bear Brook), that are between 17 and 25 years old. Net N and P mineralization rates were determined along with microbial biomass, enzyme activities and soil C, N and P stoichiometry. Total C and N concentrations in the organic layer (Oe+Oa horizon) increased significantly due to long-term fertilization in Harvard Forest and the same trend was observed in the two other experiments that are based on lower N fertilization rates. Contrariwise, total P concentrations in the organic layer decreased on average by 15% due to N fertilization, while C:P ratios increased by 60%. Phosphatase activity was elevated in the N fertilized soils in all experiments by a factor of 2 to 5, and the ratio of chitinase:phosphatase activity was on average decreased by 30%, indicating that specifically phosphatase production was upregulated. The results imply that trees and/or microorganisms invested more N in the production of phosphatases in the N fertilized soils than in the non-fertilized controls. Net P mineralization did not change consistently with N inputs, indicating that mineralized P was quickly taken up by the plants in most of the N fertilized soils. In contrast, net N mineralization increased in all experiments in response to N fertilization, while microbial biomass C was only little affected by N fertilization In conclusion, the experiments indicate that high inputs of N in temperate forest ecosystems lead to increased P demand and hence to increased phosphatase activity. Moreover, the decreased P concentration and the elevated C:P ratio of the organic layer indicate that P is preferentially mineralized and taken up by plants. Our results support the hypothesis that increased atmospheric N inputs are the reason for an emerging P limitation in temperate forests
Complementarity relation for irreversible process derived from stochastic energetics
When the process of a system in contact with a heat bath is described by
classical Langevin equation, the method of stochastic energetics [K. Sekimoto,
J. Phys. Soc. Jpn. vol. 66 (1997) p.1234] enables to derive the form of
Helmholtz free energy and the dissipation function of the system. We prove that
the irreversible heat Q_irr and the time lapse $Delta t} of an isothermal
process obey the complementarity relation, Q_irr {Delta t} >= k_B T S_min,
where S_min depends on the initial and the final values of the control
parameters, but it does not depend on the pathway between these values.Comment: 3 pages. LaTeX with 6 style macro
A hyperbolic conservation law and particle systems
In these notes we consider two particle systems: the totally asymmetric simple
exclusion process and the totally asymmetric zero-range process. We introduce the
notion of hydrodynamic limit and describe the partial differential equation that governs
the evolution of the conserved quantity – the density of particles p(t,.). This equation is
a hyperbolic conservation law of type ətp(p, u) + vF(p(t, u)) = 0, where the flux F is a
concave function. Taking these systems evolving on the Euler time scale tN, a central
limit theorem for the empirical measure holds and the temporal evolution of the limit
density field is deterministic. By taking the system in a reference frame with constant
velocity, the limit density field does not evolve in time. In order to have a non-trivial
limit, time needs to be speeded up and for time scales smaller than tN 4=3, there is still
no temporal evolution. As a consequence, the current across a characteristic vanishes
up to this longer time scale.Fundação para a Ciência e a Tecnologia (FCT) - bolsa SFRH/BPD/39991/2007Fundação Calouste Gulbenkian - projecto "Hydrodynamic limit of particle systems
Recently fixed carbon fuels microbial activity several meters below the soil surface
This data file (Scheibe_2022.xlsx) contains radiocarbon data of bulk soil carbon and CO2 respired in incubations from soil profiles in three climate zones (arid, mediterranean, and humid) of the Costal Cordillera of Chile down to a depth of six meters. Variable descriptions are provided in Template Info File. The data are part of a study, which investigates how soil microbial carbon cycling affects soil formation especially in the critical zone by understanding the carbon source of microbial activity in deep soil. The study was conducted within the framework of the Deep EarthShape priority program funded by the German Science Foundation (DFG-SPP 1803)
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