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2153 KiB

Open AccessArticle

Amines in the Earth’s Atmosphere: A Density Functional Theory Study of the Thermochemistry of Pre-Nucleation Clusters

by Alexey B. Nadykto, Fangqun Yu, Marina V. Jakovleva, Jason Herb and Yisheng Xu

Entropy 2011, 13(2), 554-569; https://doi.org/10.3390/e13020554 - 21 Feb 2011

Cited by 150 | Viewed by 13526

Abstract

The impact of organic species which are present in the Earth’s atmosphere on the burst of new particles is critically important for the understanding of the molecular nature of atmospheric nucleation phenomena. Amines have recently been proposedas possible stabilizers of binary pre-nucleation [...] Read more.

The impact of organic species which are present in the Earth’s atmosphere on the burst of new particles is critically important for the understanding of the molecular nature of atmospheric nucleation phenomena. Amines have recently been proposedas possible stabilizers of binary pre-nucleation clusters. In order to advance the understanding of atmospheric nucleation phenomena, a quantum-chemical study of hydrogen-bonded complexes of binary sulfuric acid-water clusters with methyl-, dimethyl- and trimethylamines representing common atmospheric organic species, vegetation products and laboratory impurities has been carried out. The thermochemical stability of the sulfuric acid-amines-water complexes was found to be higher than that of the sulfuric acid-ammonia-water complexes, in qualitative agreement with the previous studies. However, the enhancement in stability due to amines appears to not be large enough to overcome the difference in typical atmospheric concentrations of ammonia and amines. Further research is needed in order to address the existing uncertainties and to reach a final conclusion about the importance of amines for the atmospheric nucleation. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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115 KiB

Open AccessArticle

Lagrange Equations Coupled to a Thermal Equation: Mechanics as Consequence of Thermodynamics

by Christian Gruber and Sylvain D. Brechet

Entropy 2011, 13(2), 367-378; https://doi.org/10.3390/e13020367 - 31 Jan 2011

Cited by 11 | Viewed by 7591

Abstract

Following the analytic approach to thermodynamics developed by Stückelberg, we study the evolution equations of a closed thermodynamic system consisting of point particles in a fluid. We obtain a system of coupled differential equations describing the mechanical and the thermal evolution of the [...] Read more.

Following the analytic approach to thermodynamics developed by Stückelberg, we study the evolution equations of a closed thermodynamic system consisting of point particles in a fluid. We obtain a system of coupled differential equations describing the mechanical and the thermal evolution of the system. The coupling between these evolution equations is due to the action of a viscous friction term. Finally, we apply our coupled evolution equations to study the thermodynamics of an isolated system consisting of identical point particles interacting through a harmonic potential. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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227 KiB

Open AccessArticle

Analysis of Stability and Bifurcation in Nonlinear Mechanics with Dissipation

by Claude Stolz

Entropy 2011, 13(2), 332-366; https://doi.org/10.3390/e13020332 - 31 Jan 2011

Cited by 3 | Viewed by 6185

Abstract

The analysis of stability and bifurcation is studied in nonlinear mechanics with dissipative mechanisms: plasticity, damage, fracture. The description is based on introduction of a set of internal variables. This framework allows a systematic description of the material behaviour via two potentials: the [...] Read more.

The analysis of stability and bifurcation is studied in nonlinear mechanics with dissipative mechanisms: plasticity, damage, fracture. The description is based on introduction of a set of internal variables. This framework allows a systematic description of the material behaviour via two potentials: the free energy and the potential of dissipation. In the framework of standard generalized materials the internal state evolution is governed by a variational inequality which depends on the mechanism of dissipation. This inequality is obtained through energetic considerations in an unified description based upon energy and driving forces associated to the dissipative process. This formulation provides criterion for existence and uniqueness of the system evolution. Examples are presented for plasticity, fracture and for damaged materials. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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158 KiB

Open AccessArticle

Spin-Currents and Spin-Pumping Forces for Spintronics

by Jean-Eric Wegrowe and Henri-Jean Drouhin

Entropy 2011, 13(2), 316-331; https://doi.org/10.3390/e13020316 - 28 Jan 2011

Cited by 15 | Viewed by 7705

Abstract

A general definition of the Spintronics concept of spin-pumping is proposed as generalized forces conjugated to the spin degrees of freedom in the framework of the theory of mesoscopic non-equilibrium thermodynamics. It is shown that at least three different kinds of spin-pumping forces [...] Read more.

A general definition of the Spintronics concept of spin-pumping is proposed as generalized forces conjugated to the spin degrees of freedom in the framework of the theory of mesoscopic non-equilibrium thermodynamics. It is shown that at least three different kinds of spin-pumping forces and associated spin-currents can be defined in the most simple spintronics system: the Ferromagnetic/Non-Ferromagnetic metal interface. Furthermore, the generalized force associated with the ferromagnetic collective variable is also introduced on an equal footing to describe the coexistence of the spin of the conduction electrons (paramagnetic spins attached to s-band electrons) and the ferromagnetic-order parameter. The dynamical coupling between these two kinds of magnetic degrees of freedom is presented and interpreted in terms of spin-transfer effects. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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229 KiB

Open AccessArticle

Burning Speed and Entropy Production Calculation of a Transient Expanding Spherical Laminar Flame Using a Thermodynamic Model

by Kian Eisazadeh-Far, Ali Moghaddas, Faranak Rahim and Hameed Metghalchi

Entropy 2010, 12(12), 2485-2496; https://doi.org/10.3390/e12122485 - 21 Dec 2010

Cited by 30 | Viewed by 8238

Abstract

A thermodynamic model has been developed to calculate burning speed and entropy production of transient expending spherical laminar flame in an enclosed vessel. The model also predicts the particle trajectories of both unburned and burned gases in the vessel. The input to this [...] Read more.

A thermodynamic model has been developed to calculate burning speed and entropy production of transient expending spherical laminar flame in an enclosed vessel. The model also predicts the particle trajectories of both unburned and burned gases in the vessel. The input to this model is the dynamic pressure rise due to combustion process. The unburned gases are divided into three regions: The core unburned gases which are compressed isentropically, the vessel walls and electrodes boundary layer gases, and gases in the preheat zone of the flames. The burned gases are in many shells having the same pressure but different temperatures. The model also includes radiation losses from the burned gases to vessel walls. Entropy production due to irreversibility has been calculated by applying entropy balance to the gas mixtures. Burning speed of premixed n-decane air mixture has been reported for temperatures and pressures along an isentrope. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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145 KiB

Open AccessArticle

Reconsideration of Criteria and Modeling in Order to Optimize the Efficiency of Irreversible Thermomechanical Heat Engines

by Michel Feidt

Entropy 2010, 12(12), 2470-2484; https://doi.org/10.3390/e12122470 - 21 Dec 2010

Cited by 9 | Viewed by 7031

Abstract

The purpose of this work is to precise and complete one recently proposed in the literature and relative to a general criterion to maximize the first law efficiency of irreversible heat engines. It is shown that the previous proposal seems to be a [...] Read more.

The purpose of this work is to precise and complete one recently proposed in the literature and relative to a general criterion to maximize the first law efficiency of irreversible heat engines. It is shown that the previous proposal seems to be a particular case. A new proposal has been developed for a Carnot irreversible thermomechanical heat engine at steady state associated to two infinite heat reservoirs (hot source, and cold sink): this constitutes the studied system. The presence of heat leak is accounted for, with the most simple form, as is done generally in the literature. Irreversibility is modeled through , created internal entropy rate in the converter (engine), and , total created entropy rate in the system. Heat transfer laws are represented as general functions of temperatures. These concepts are particularized to the most common heat transfer law (linear one). Consequences of the proposal are examined; some new analytical results are proposed for efficiencies. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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671 KiB

Open AccessArticle

All in Action

by Arto Annila

Entropy 2010, 12(11), 2333-2358; https://doi.org/10.3390/e12112333 - 19 Nov 2010

Cited by 66 | Viewed by 10294

Abstract

The principle of least action provides a holistic worldview in which Nature in its entirety and every detail is described in terms of actions. Each and every action is ultimately composed of one or multiple of the most elementary actions which relates to [...] Read more.

The principle of least action provides a holistic worldview in which Nature in its entirety and every detail is described in terms of actions. Each and every action is ultimately composed of one or multiple of the most elementary actions which relates to Planck’s constant. Elements of space are closed actions, known as fermions, whereas elements of time are open actions, known as bosons. The actions span an energy landscape, the Universe, which evolves irreversibly according to the 2nd law of thermodynamics by diminishing energy density differences in least time. During evolution densely-curled actions unfold step-by-step when opening up and expelling one or multiple elementary actions to their surrounding sparser space. The energy landscape will process from one symmetry group to another until the equivalence to its dual, i.e., the surrounding density has been attained. The scale-free physical portrayal of nature in terms of actions does not recognize any fundamental difference between fundamental particles and fundamental forces. Instead a plethora of particles and a diaspora of forces are perceived merely as diverse manifestations of a natural selection for various mechanisms and ways to decrease free energy in the least time. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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373 KiB

Open AccessArticle

A Statistical Thermodynamical Interpretation of Metabolism

by Friedrich Srienc and Pornkamol Unrean

Entropy 2010, 12(8), 1921-1935; https://doi.org/10.3390/e12081921 - 17 Aug 2010

Cited by 20 | Viewed by 9147

Abstract

The metabolic network of a cell can be decomposed into discrete elementary modes that contribute, each with a certain probability, to the overall flux through the metabolism. These modes are cell function supporting, fundamental pathways that represent permissible ‘quantum’ states of the metabolism. [...] Read more.

The metabolic network of a cell can be decomposed into discrete elementary modes that contribute, each with a certain probability, to the overall flux through the metabolism. These modes are cell function supporting, fundamental pathways that represent permissible ‘quantum’ states of the metabolism. For the case that cellular regulatory mechanisms for pathway fluxes evolved in an unbiased way, we demonstrate theoretically that the usage probabilities of individual elementary modes are distributed according to Boltzmann’s distribution law such that the rate of entropy production is maximized. Such distribution can be observed experimentally in highly evolved metabolic networks. Therefore, cell function has a natural tendency to operate at a maximum rate of entropy generation using preferentially efficient pathways with small reaction entropies. Ultimately, evolution of metabolic networks appears to be driven by forces that can be quantified by the distance of the current metabolic state from the state of maximum entropy generation that represents the unbiased, most probable selection of fundamental pathway choices. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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86 KiB

Open AccessCommentary

A Comment on Nadytko et al., “Amines in the Earth’s Atmosphere: A Density Functional Theory Study of the Thermochemistry of Pre-Nucleation Clusters”. Entropy 2011, 13, 554–569

by Theo Kurtén

Entropy 2011, 13(4), 915-923; https://doi.org/10.3390/e13040915 - 19 Apr 2011

Cited by 17 | Viewed by 8138

Abstract

Nadykto, Yu, Jakovleva, Herb and Xu have recently reported a DFT study on the structure and formation thermodynamics of sulfuric acid-base-water clusters, with ammonia and a handful of amines as bases [1]. This study partially overlaps with our previous work [2], and a [...] Read more.

Nadykto, Yu, Jakovleva, Herb and Xu have recently reported a DFT study on the structure and formation thermodynamics of sulfuric acid-base-water clusters, with ammonia and a handful of amines as bases [1]. This study partially overlaps with our previous work [2], and a significant part of the discussion in their manuscript concerns differences between their results and ours. This comment is intended to address some issues related to that discussion. Specifically, it is shown that the errors related to basis-set effects in our calculations are very likely much smaller than claimed by Nadykto et al. [1]. Composite calculations including e.g., higher-level electron correlation also agree better with our results. Full article

(This article belongs to the Special Issue Advances in Thermodynamics)

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