Search results for "Thermodynamic"

Future CMB cosmological constraints in a dark coupled universe

2010

Cosmic microwave background satellite missions as the ongoing Planck experiment are expected to provide the strongest constraints on a wide set of cosmological parameters. Those constraints, however, could be weakened when the assumption of a cosmological constant as the dark energy component is removed. Here we show that it will indeed be the case when there exists a coupling among the dark energy and the dark matter fluids. In particular, the expected errors on key parameters as the cold dark matter density and the angular diameter distance at decoupling are significantly larger when a dark coupling is introduced. We show that it will be the case also for future satellite missions as EPIC…

Evaporation of Near-Extremal Reissner-Nordström Black Holes

2000

The formation of near-extremal Reissner-Nordstrom black holes in the S-wave approximation can be described, near the event horizon, by an effective solvable model. The corresponding one-loop quantum theory remains solvable and allows to follow analytically the evaporation process which is shown to require an infinite amount of time.

Atmospheric aging of small-scale wood combustion emissions (model MECHA 1.0) – is it possible to distinguish causal effects from non-causal ass…

2020

Abstract. Primary emissions of wood combustion are complex mixtures of hundreds or even over a thousand compounds, which pass through a series of chemical reactions and physical transformation processes in the atmosphere (aging). This aging process depends on atmospheric conditions, such as concentration of atmospheric oxidizing agents (OH radical, ozone and nitrate radicals), humidity and solar radiation, and is known to strongly affect the characteristics of atmospheric aerosols. However, there are only few models that are able to represent the aging of emissions during its lifetime in the atmosphere. In this work, we implemented a model (Model for aging of Emissions in environmental CHAm…

Simulation of organics in the atmosphere: evaluation of EMACv2.54 with the Mainz Organic Mechanism (MOM) coupled to the ORACLE (v1.0) submodel

2021

Abstract. An updated and expanded representation of organics in the chemistry general circulation model EMAC (ECHAM5/MESSy for Atmospheric Chemistry) has been evaluated. First, the comprehensive Mainz Organic Mechanism (MOM) in the submodel MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere) was activated with explicit degradation of organic species up to five carbon atoms and a simplified mechanism for larger molecules. Second, the ORACLE submodel (version 1.0) considers now condensation on aerosols for all organics in the mechanism. Parameterizations for aerosol yields are used only for the lumped species that are not included in the explicit mechanism. The simultaneous…

2016

Abstract. Particle concentration measurements with underwing probes on aircraft are impacted by air compression upstream of the instrument body as a function of flight velocity. In particular, for fast-flying aircraft the necessity arises to account for compression of the air sample volume. Hence, a correction procedure is needed to invert measured particle number concentrations to ambient conditions that is commonly applicable to different instruments to gain comparable results. In the compression region where the detection of particles occurs (i.e. under factual measurement conditions), pressure and temperature of the air sample are increased compared to ambient (undisturbed) conditions i…

Electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition.

2005

International audience; The electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350–1018°C. Large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure. The samples were analyzed by electron microprobe. The relative proportions of the phases as a function of temperature were determined. Depending on temperature, the phase assemblies included quenched silicate liquid, ±plagioclase, ±pyroxene, ±Fe-Ti oxides. The crystal content varied from 0 to 80 wt %. In response to partial crystallization, the residual liquid changed composition from basalt, t…

Lagrangian simulations of stable isotopes in water vapor: An evaluation of nonequilibrium fractionation in the Craig-Gordon model

2009

[1] The Craig-Gordon model is the basis for the parameterization of water isotope fractionation during evaporation from the ocean in many atmospheric isotope models. Its exact formulation (e.g., with respect to the nonequilibrium fractionation factor k) is mainly based on theoretical considerations and not very well constrained by observations. This study addresses this issue by combining a recently developed Lagrangian moisture source analysis with a Craig-Gordon fractionation parameterization for the identified evaporation events in order to model isotope ratios in water vapor. This technique is applied to 45 measurement days of isotopes in water vapor at Rehovot (Israel) during the years…

A reexamination of the equilibrium conditions in the theory of water drop nucleation

1975

The thermodynamic equations necessary to describe the conditions for equilibrium between a highly curved surface of a liquid and its vapour are re-examined. The complete equilibrium behaviour is reduced to one single differential equation for each component in an arbitrary c -component system. It is shown that this general formulation can be specialized to describe the conditions for equilibrium between water vapour and a pure water drop, the drop carrying an electric charge, containing a water soluble substance and/or containing a water insoluble nucleus. In the light of the present formulation, some incorrect physical statements of treatments by various authors reported in literature are …

Comparative study on immersion freezing utilizing single-droplet levitation methods

2021

Immersion freezing experiments were performed utilizing two distinct single-droplet levitation methods. In the Mainz vertical wind tunnel, supercooled droplets of 700 µm diameter were freely floated in a vertical airstream at constant temperatures ranging from −5 to −30 ∘C, where heterogeneous freezing takes place. These investigations under isothermal conditions allow the application of the stochastic approach to analyze and interpret the results in terms of the freezing or nucleation rate. In the Mainz acoustic levitator, 2 mm diameter drops were levitated while their temperature was continuously cooling from +20 to −28 ∘C by adapting to the ambient temperature. Therefore, in this case th…

New investigations on homogeneous ice nucleation: the effects of water activity and water saturation formulations

2022

Laboratory measurements at the AIDA cloud chamber and airborne in-situ observations suggest that the homogeneous freezing thresholds at low temperatures are possibly higher than expected from the so-called “Koop-line”. This finding is of importance, because the ice onset relative humidity affects the cirrus cloud coverage and, at the very low temperatures of the tropical tropopause layer, together with the number of ice crystals also the transport of water vapor into the stratosphere. Both, the appearance of cirrus clouds and the amount of stratospheric water feed back to the radiative budget of the atmosphere. In order to explore the enhanced ice onset humidities, we re-examine…