338 research outputs found
Theory and observations: Model simulations of the period 1955-1985
The main objective of the theoretical studies presented here is to apply models of stratospheric chemistry and transport in order to understand the processes that control stratospheric ozone and that are responsible for the observed variations. The model calculations are intended to simulate the observed behavior of atmospheric ozone over the past three decades (1955-1985), for which there exists a substantial record of both ground-based and, more recently, satellite measurements. Ozone concentrations in the atmosphere vary on different time scales and for several different causes. The models described here were designed to simulate the effect on ozone of changes in the concentration of such trace gases as CFC, CH4, N2O, and CO2. Changes from year to year in ultraviolet radiation associated with the solar cycle are also included in the models. A third source of variability explicitly considered is the sporadic introduction of large amounts of NO sub x into the stratosphere during atmospheric nuclear tests
Temperature-dependent quantum pair potentials and their application to dense partially ionized hydrogen plasmas
Extending our previous work \cite{filinov-etal.jpa03ik} we present a detailed
discussion of accuracy and practical applications of finite-temperature
pseudopotentials for two-component Coulomb systems. Different pseudopotentials
are discussed: i) the diagonal Kelbg potential, ii) the off-diagonal Kelbg
potential iii) the {\em improved} diagonal Kelbg potential, iv) an effective
potential obtained with the Feynman-Kleinert variational principle v) the
``exact'' quantum pair potential derived from the two-particle density matrix.
For the {\em improved} diagonal Kelbg potential a simple temperature dependent
fit is derived which accurately reproduces the ``exact'' pair potential in the
whole temperature range. The derived pseudopotentials are then used in path
integral Monte Carlo (PIMC) and molecular dynamics (MD) simulations to obtain
thermodynamical properties of strongly coupled hydrogen. It is demonstrated
that classical MD simulations with spin-dependent interaction potentials for
the electrons allow for an accurate description of the internal energy of
hydrogen in the difficult regime of partial ionization down to the temperatures
of about K. Finally, we point out an interesting relation between the
quantum potentials and effective potentials used in density functional theory.Comment: 18 pages, 11 figure
A descriptive study of adrenal crises in adults with adrenal insufficiency: increased risk with age and in those with bacterial infections
Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas
In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms
Nitrous oxide emissions from multiple combined applications of fertiliser and cattle slurry to grassland
The Tinnitus Retraining Therapy Trial (TRTT): study protocol for a randomized controlled trial
The Cost of Using Global Warming Potentials: Analysing the Trade off Between CO2, CH4 and N2O
Uncertainty estimation for operational ocean forecast products—a multi-model ensemble for the North Sea and the Baltic Sea
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