scholarly journals A Note on the Consequences of a Hot Mitochondrion: Some Recent Developments and Open Questions

2020 ◽  
Keyword(s):  
Functional Dependence ◽  
Heat Engine ◽  
Thermodynamic Efficiency ◽  
Gradient Term ◽  
Chemical Gradient ◽  
Temperature Dependent ◽  
Open Questions ◽  
Mode Of Operation ◽  
Recent Developments ◽  
Electrical Gradient

Background: Chrétien and co-workers (PLOS Biology. 2018;16(1):e2003992) recently suggested that the mitochondrion might possibly be hotter than its surrounding (by as much as 10°C). Objectives: To examine the validity of this claim and review the possible implications and repercussion of such a claim – if true – on some aspects of mitochondrial biochemistry and biophysics. Results: Both the chemical gradient and the electrical gradient Gibbs energy terms in the central equation of chemiosmotic theory are temperature dependent, the first explicitly and the second implicitly. A hotter mitochondrion – as claimed – would imply a 3% correction in the chemical gradient term, but we cannot estimate the corresponding effect on the electrical term at this time since the functional dependence of the voltage on the temperature is not known to the best of the authors’ knowledge. Further, if this claim is true and to the extent claimed (10°C), this may imply some heat-engine character for mitochondrial thermodynamic operation albeit this may only represent 4% at most. Conclusions: Doubts and criticisms regarding the suggestion of a hotter mitochondrion have been raised and are briefly discussed. These doubts are contrasted with some data and considerations that support the claim of a hotter mitochondrion. It is concluded that the mitochondrion is probably hotter than its environment but not to the extent claimed by Chrétien et al. and that the thermodynamic efficiency and the mode of operation of the mitochondrion as an electrochemical battery are very slightly perturbed by even the maximum claimed revision of the temperature of its operation.

scholarly journals Learning the best nanoscale heat engines through evolving network topology

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuto Ashida ◽  
Takahiro Sagawa
Keyword(s):  
Network Topology ◽  
Heat Engine ◽  
Search Space ◽  
Single Electron ◽  
Thermodynamic Efficiency ◽  
Full Potential ◽  
Thermal Systems ◽  
Nanoscale Systems ◽  
Heat Engines ◽  
Many Body Interactions

AbstractThe quest to identify the best heat engine has been at the center of science and technology. Considerable studies have so far revealed the potentials of nanoscale thermal machines to yield an enhanced thermodynamic efficiency in noninteracting regimes. However, the full benefit of many-body interactions is yet to be investigated; identifying the optimal interaction is a hard problem due to combinatorial explosion of the search space, which makes brute-force searches infeasible. We tackle this problem with developing a framework for reinforcement learning of network topology in interacting thermal systems. We find that the maximum possible values of the figure of merit and the power factor can be significantly enhanced by electron-electron interactions under nondegenerate single-electron levels with which, in the absence of interactions, the thermoelectric performance is quite low in general. This allows for an alternative strategy to design the best heat engines by optimizing interactions instead of single-electron levels. The versatility of the developed framework allows one to identify full potential of a broad range of nanoscale systems in terms of multiple objectives.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

scholarly journals Recent developments on the Stieltjes transform of generalized functions

1987 ◽  
Vol 10 (4) ◽  
pp. 641-670 ◽  
Author(s):  
Ram Sankar Pathak ◽  
Lokenath Debnath
Keyword(s):  
Final Section ◽  
Generalized Functions ◽  
Stieltjes Transform ◽  
Poisson Transform ◽  
Open Questions ◽  
The Laplace Transform ◽  
Recent Developments ◽  
The Subject ◽  
Abelian Theorems ◽  
Stieltjes Transforms

This paper is concerned with recent developments on the Stieltjes transform of generalized functions. Sections 1 and 2 give a very brief introduction to the subject and the Stieltjes transform of ordinary functions with an emphasis to the inversion theorems. The Stieltjes transform of generalized functions is described in section 3 with a special attention to the inversion theorems of this transform. Sections 4 and 5 deal with the adjoint and kernel methods used for the development of the Stieltjes transform of generalized functions. The real and complex inversion theorems are discussed in sections 6 and 7. The Poisson transform of generalized functions, the iteration of the Laplace transform and the iterated Stieltjes transfrom are included in sections 8, 9 and 10. The Stieltjes transforms of different orders and the fractional order integration and further generalizations of the Stieltjes transform are discussed in sections 11 and 12. Sections 13, 14 and 15 are devoted to Abelian theorems, initial-value and final-value results. Some applications of the Stieltjes transforms are discussed in section 16. The final section deals with some open questions and unsolved problems. Many important and recent references are listed at the end.

scholarly journals Dynamic Mechanism Design: An Introduction

2019 ◽  
Vol 57 (2) ◽  
pp. 235-274 ◽  
Author(s):  
Dirk Bergemann ◽  
Juuso Välimäki
Keyword(s):  
Mechanism Design ◽  
Dynamic Environment ◽  
Limited Liability ◽  
Dynamic Mechanism ◽  
Dynamic Mechanism Design ◽  
Dynamic Mechanisms ◽  
Sequential Screening ◽  
Open Questions ◽  
Recent Developments ◽  
Primary Focus

We provide an introduction to the recent developments of dynamic mechanism design, with a primary focus on the quasilinear case. First, we describe socially optimal (or efficient) dynamic mechanisms. These mechanisms extend the well-known Vickrey– Clark–Groves and D’Aspremont–Gérard–Varet mechanisms to a dynamic environment. Second, we discuss revenue optimal mechanisms. We cover models of sequential screening and revenue-maximizing auctions with dynamically changing bidder types. We also discuss models of information management where the mechanism designer can control (at least partially) the stochastic process governing the agents’ types. Third, we consider models with changing populations of agents over time. After discussing related models with risk-averse agents and limited liability, we conclude with a number of open questions and challenges that remain for the theory of dynamic mechanism design. ( JEL D44, D81, D82)

Ion transport in polymeric ionic liquids: recent developments and open questions

2019 ◽  
Vol 4 (2) ◽  
pp. 280-293 ◽  
Author(s):  
Venkat Ganesan
Keyword(s):  
Ionic Liquids ◽  
Ion Transport ◽  
Charge Transport ◽  
Transport Mechanisms ◽  
Polymeric Ionic Liquids ◽  
Open Questions ◽  
Recent Developments

Recent developments and outstanding questions in the context of charge transport mechanisms in polymeric ionic liquids are highlighted.

Thermo-Mechanical Modeling of a Shape Memory Alloy Heat Engine

2011 ◽  
Author(s):  
Christopher B. Churchill ◽  
John Shaw
Keyword(s):  
Heat Transfer ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Heat Engine ◽  
The United States ◽  
Thermodynamic Efficiency ◽  
Low Grade ◽  
Heat Engines ◽  
Deformation Mechanics ◽  
Sma Spring

Two thirds of the energy generated in the United States is currently lost as waste heat, representing a potentially vast source of green energy. Low Carnot efficiency is an inherent limitation of extracting energy from low-grade thermal sources (temperature gradients near or below 100C), and SMA heat engines could be useful for those applications where low weight and packaging are overriding considerations. Although many shape memory alloy (SMA) heat engines have been proposed to harvest this energy, and a few have been built and demonstrated in past decades, they have not been commercially successful. Some of the barriers to commercialization include their perceived low thermodynamic efficiency, high material cost, low material durability, complexities when using fluid baths, and the lack of robust constitutive models and design tools. Recent advances, however, in SMA longevity, reductions in materials costs (as production volumes have increased), and a better understanding of SMA behavior have stimulated new research on SMA heat engines. The Lightweight Thermal Energy Recovery System (LighTERS) is an ongoing ARPA-E funded collaboration between General Motors, HRL Laboratories, Dynalloy, Inc., and the University of Michigan. In the LighTERS engine (a refinement of the Dr. Johnson engine), a closed loop SMA spring element generates mechanical power by pulling itself between alternating hot and cold air regions. The first known thermo-mechanical model for this type of heat engine was developed in three stages. First, the constitutive and heat transfer relationships of an SMA spring form were characterized experimentally. Second, those relationships were used as inputs in a steady-state model of the heat engine, including both convective heat transfer and large-deformation mechanics. Finally, the model was validated successfully against measurements of a experimental heat engine built at HRL Labs.

scholarly journals Recent developments and open questions in the field of semantic roles

2014 ◽  
Vol 38 (3) ◽  
pp. 437-462 ◽  
Author(s):  
Seppo Kittilä ◽  
Fernando Zúñiga
Keyword(s):  
Previous Literature ◽  
Semantic Roles ◽  
Linguistic Data ◽  
Open Questions ◽  
Recent Developments

This introductory chapter briefly introduces a few milestones in the voluminous previous literature on semantic roles, and charts the territory in which the papers of this volume aim to make a contribution. This territory is characterized by fairly disparate conceptualizations of semantic roles and their status in theories of grammar and the lexicon, as well as by diverse and probably complementary ways of deriving or identifying them based on linguistic data. Particular attention is given to the question of how selected roles appear to relate to each other, and we preliminarily address the issue of how roles, subroles, and role complexes are best thought of in general.

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