Statistical Mechanics of the Human Placenta: A Stationary State of a Near-Equilibrium System in a Linear Regime

All near-equilibrium systems under linear regime evolve to stationary states in which there is constant entropy production rate. In an open chemical system that exchanges matter and energy with the exterior, we can identify both the energy and entropy flows associated with the exchange of matter and energy. This can be achieved by applying statistical mechanics (SM), which links the microscopic properties of a system to its bulk properties. In the case of contractile tissues such as human placenta, Huxley’s equations offer a phenomenological formalism for applying SM. SM was investigated in human placental stem villi (PSV) (n = 40). PSV were stimulated by means of KCl exposure (n = 20) and tetanic electrical stimulation (n = 20). This made it possible to determine statistical entropy (S), internal energy (E), affinity (A), thermodynamic force (A / T) (T: temperature), thermodynamic flow (v) and entropy production rate (A / T x v). We found that PSV operated near equilibrium, i.e., A ≺≺ 2500 J/mol and in a stationary linear regime, i.e., (A / T) varied linearly with v. As v was dramatically low, entropy production rate which quantified irreversibility of chemical processes appeared to be the lowest ever observed in any contractile system.     

A thermodynamic theory of evolution

As a closed thermodynamic system subject to an essentially constant free energy gradient, the biosphere must evolve toward a stationary state of maximum structuring and minimum dissipation with respect to this applied gradient. Since biological evolution occurs opportunistically through chance and selection, rather than as a direct response to the free energy gradient, the conformance of this phase of evolution with thermodynamics requires that natural selection, and the particular adaptive strategies employed by species of organisms, be related to the principles of increasing structuring and decreasing dissipation. In this paper, some general features of this relationship are proposed.     

Ecosystem growth and development

One of the most important features of biosystems is how they are able to maintain local order (low entropy) within their system boundaries. At the ecosystem scale, this organization can be observed in the thermodynamic parameters that describe it, such that these parameters can be used to track ecosystem growth and development during succession. Thermodynamically, ecosystem growth is the increase of energy throughflow and stored biomass, and ecosystem development is the internal reorganization of these energy mass stores, which affect transfers, transformations, and time lags within the system. Several proposed hypotheses describe thermodynamically the orientation or natural tendency that ecosystems follow during succession, and here, we consider five: minimize specific entropy production, maximize dissipation, maximize exergy storage (includes biomass and information), maximize energy throughflow, and maximize retention time. These thermodynamic orientors were previously all shown to occur to some degree during succession, and here we present a refinement by observing them during different stages of succession. We view ecosystem succession as a series of four growth and development stages: boundary, structural, network, and informational. We demonstrate how each of these ecological thermodynamic orientors behaves during the different growth and development stages, and show that while all apply during some stages only maximizing energy throughflow and maximizing exergy storage are applicable during all four stages. Therefore, we conclude that the movement away from thermodynamic equilibrium, and the subsequent increase in organization during ecosystem growth and development, is a result of system components and configurations that maximize the flux of useful energy and the amount of stored exergy. Empirical data and theoretical models support these conclusions.     

生态学研究中的分析与能值分析理论

与能值是研究生态系统自组织过程的两个重要的目标函数。分析与能值分析理论在 2 0世纪 70年代开始应用于生态学研究 ,它们有各自的理论起点 ,在应用上从不同的角度表现生态系统功能 ,两者的互补关系受到了生态学家的关注 ,并在实际应用中取得了有益的研究成果。从与能值各自的理论基础与研究成果出发 ,概述了两者在描述生态系统功能上的互补关系 ,并分析了其在生态学理论研究及实际应用上的重要意义     

喀左县农业生态系统能流的研究

本文根据辽宁省西部一个典型具(喀左县)农业生态系统的调查,分析该系统八十年代初期基本特征,进而提出改善该农业生态系统的措施。 整个系统由七个组分(或亚系统)组成(农田、牲畜、果园、人工林、人工草地、天然灌丛草地、当地居民)。作者根据有关统计数据和调查资料估算出该系统1981—1983年期间年平均流量,其中包括流入和流出能量以及系统内各组分之间的能流量。最后讨论了调整畜牧业结构,提高工业能量、生物质能量利用率和林分改造等问题。     

Transient kinetics of thermodynamic buffering

The transient response of mitochondrial ATP production towards perturbations was studied by analyzing the trajectories leading from arbitrary initial conditions of the adenine nucleotide pool to the final steady state. These trajectories were calculated from differential equations based on linear relations between flows and thermodynamic forces of the adenylate kinase system including oxidative phosphorylation. The motion of the system along the trajectories consists of two phases: (1) a rapid phase leading from initial states to a common relaxation curve; and (2) a slow phase leading along the relaxation curve to the final steady state. The first phase corresponds to a motion close to the loci of constant adenylic energy charge. In line with this observation is the finding that the energy charge is a constant of motion of the adenylate kinase reaction. The second phase corresponds to a motion along a relaxation curve characterized by minimal Lyapunov exponents in the concentration space of the adenine nucleotides. Thus, both phases of the transient kinetics can be approximated in terms of thermodynamic functions to a high degree of precision. Incubations with isolated rat liver mitochondria were in excellent agreement with the theoretical predictions. In summary, these studies show that the adenylate kinase system not only optimizes the efficiency of oxidative phosphorylation through thermodynamic buffering but, in addition, also deeply influences the transient response of the whole system.     

Gaia again

The ideas of the Gaia hypothesis from the 1960s are today largely included in global ecology and Earth system sciences. The interdependence between biosphere, oceans, atmosphere and geosphere is well-established by data from global monitoring. Nevertheless the theory underlying the holistic view of the homeostatic Earth has remained obscure. Here the foundations of Gaia theory are examined from the recent formulation of the 2nd law of thermodynamics as an equation of motion. According to the principle of increasing entropy, all natural processes, inanimate just as animate, consume free energy, the thermodynamic driving force. All species, abiotic just as biotic are viewed as mechanisms of energy transduction for the global system to evolve toward a stationary state in its surroundings. The maximum entropy state displays homeostasis by being stable against internal fluctuations. When surrounding conditions change or when new mechanisms emerge, the global system readjusts its flows of energy to level newly appeared gradients. Thus, the propositions of Gaia theory and holistic understanding of the global system are recognized as consequences of thermodynamic imperatives.     

Thermodynamic view on decision-making process: emotions as a potential power vector of realization of the choice

This research is devoted to possible mechanisms of decision-making in frames of thermodynamic principles. It is also shown that the decision-making system in reply to emotion includes vector component which seems to be often a necessary condition to transfer system from one state to another. The phases of decision-making system can be described as supposed to be nonequilibrium and irreversible to which thermodynamics laws are applied. The mathematical model of a decision choice, proceeding from principles of the nonlinear dynamics considering instability of movement and bifurcation is offered. The thermodynamic component of decision-making process on the basis of vector transfer of energy induced by emotion at the given time is surveyed. It is proposed a three-modular model of decision making based on principles of thermodynamics. Here it is suggested that at entropy impact due to effect of emotion, on the closed system—the human brain,—initially arises chaos, then after fluctuations of possible alternatives which were going on—reactions of brain zones in reply to external influence, an order is forming and there is choice of alternatives, according to primary entrance conditions and a state of the closed system. Entropy calculation of a choice expectation of negative and positive emotion shows judgment possibility of existence of “the law of emotion conservation” in accordance with several experimental data.     

A thermodynamical study of the clockwork hypothesis proposed by E. Schrödinger

In the present study, the 'clockwork' hypothesis proposed by Schr?dinger was examined from the viewpoint of thermodynamics. Firstly, noticing a unidirectional transfer of entropy in a heat engine, the logic was briefly explained about a close relation between this entropy transfer and an irreversible cycle performed by a working body. Next, paying attention to two fundamental differences between a heat engine and a biological system, we considered an isolated system Asigma consisting of three one-component systems (Ai, A, Ao) and noted a case that the same molecules as the component ones flowed quasistatically into Ai from the outside. Then, the unidirectional flows of the molecules, energy and entropy, which were induced by the above inflow in Asigma, were formulated on the basis of the equilibrium thermodynamics for an open system. Furthermore, it was clarified that the fundamental equation for these flows is the Schr?dinger inequality and that the necessary-sufficient condition for this inequality is the existence of an irreversible cycle performed by A. Here A corresponds to a working body in a heat engine. It was, thus, concluded that the 'clockwork' hypothesis by Schr?dinger is considered to be reasonable for a biological system composed of various irreversible subsystems.     

Entropy and the conceit of biodiversity management

Many conservation biologists and ecologists consider invasive species to be one of the greatest threats to biodiversity because their spread across biogeographical boundaries may endanger unique and localized expressions of biodiversity (whether species or communities). Consequently, they imagine a future, the ‘Homogocene’, in which a small set of species dominates ecosystems around the world, and they promote policies and practices to lessen the spread of these species. Here, we consider some thermodynamic dimensions of the efforts to maintain current biogeographical boundaries. We wish to explore an important conceptual analogy between thermodynamically‐closed systems and isolated biogeographical regions in ecology. The conceptual tools developed in the context of thermodynamic systems can be shown to have relevance in a wide variety of systems contexts. The ‘Maxwell's demon’ thought experiment suggests that entropy is best thought of as information‐relative rather than a ‘law of nature’. Adopting this Maxwellian thermodynamic approach to managing complexity can shed new light on the challenges of biodiversity management. To prevent the dispersion of invasive species, people must invest energy on a scale to counteract global trade and concomitant dispersal of species. We show that removing barriers to species interaction through globalization is akin to allowing a previously isolated thermal system to interact with its environment; in both cases, the system will tend towards mixing or ‘equilibrium’, and fighting this tendency is costly. Unless social and economic integration declines, the energetic input required to lessen the spread of invasive species will continue to grow.     

An open system framework for integrating critical zone structure and function

The ??critical zone?? includes the coupled earth surface systems of vegetation, regolith and groundwater that are essential to sustaining life on the planet. The function of this zone is the result of complex interactions among physical, chemical and biological processes and understanding these interactions remains a major challenge to earth system sciences. Here we develop an integrated framework based on thermodynamic theory to characterize the critical zone as a system open to energy and mass fluxes that are forced by radiant, geochemical, and elevational gradients. We derive a statement that demonstrates the relative importance of solar radiation, water, carbon, and physical/chemical denudation mass fluxes to the critical zone energy balance. Within this framework we use rates of effective energy and mass transfer [EEMT; W m^?2] to quantify the relevant flux-gradient relations. Synthesis of existing data demonstrates that variation in energetics associated with primary production and effective precipitation explains substantial variance in critical zone structure and function. Furthermore, we observe threshold behavior in systems that transition to primary production predominance of the energy flux term. The proposed framework provides a first order approximation of non-linearity in critical zone processes that may be coupled with physical and numerical models to constrain landscape evolution.     

Environmental and Socioeconomic Constraints to the Development of Freshwater Fish Aquaculture in China

In this article, we provide an overview, on freshwater fish aquaculture in P.R. China, with special emphasis on pond fish culture. We describe the history, ecology (trophic structure and species reared), and technological aspects (including inputs/outputs, yields, labor productivity, and fossil energy use) of freshwater fish production and analyze its role in relation to the socioeconomic context. We discuss the prospects for intensification of production. In China, freshwater fish aquaculture has always been closely linked to cultivation of crops and animal husbandry, that is, feed inputs are in the form of agricultural wastes. The close integration with the farming system at large results in an efficient use of nutrients, low environmental loading, and little dependence on fossil energy inputs. About 7 to 9 different fish species, mainly herbivores, are kept in the same pond and efforts are made to maintain as much as possible the natural mechanisms of matter regulation and energy flows within the pond ecosystem. However, ecological compatibility is paid for by relatively low productivity, both per hectare of waterbody and per hour of labor input. If the throughput of freshwater fish production per unit of area and labor are to be dramatically increased, the equilibrium of the traditional integrated system will be difficult to maintain.     

Efficiency of energy conversion in model biological pumps: Optimization by linear nonequilibrium thermodynamic relations

Experimental investigations showed linear relations between flows and forces in some biological energy converters operating far from equilibrium. This observation cannot be understood on the basis of conventional nonequilibrium thermodynamics. Therefore, the efficiencies of a linear and a nonlinear mode of operation of an energy converter (a hypothetical redox-driven H⁺ pump) were compared. This comparison revealed that at physiological values of the forces and degrees of coupling (1) the force ratio permitting optimal efficiency was much higher in the linear than in the nonlinear mode and (2) the linear mode of operation was at least 10⁶-times more efficient that the nonlinear one. These observations suggest that the experimentally observed linear relations between flows and forces, particularly in the case of oxidative phosphorylation, may be due to a feedback regulation maintaining linear thermodynamic relations far from equilibrium. This regulation may have come about as the consequence of an evolutionary drive towards higher efficiency.     

Closed water recirculating system for fish rearing equipped with bioreactor capable of simultaneous nitrification and denitrification.

Five crucian carp, Carassius auratus langsdorfiicarps had been reared in a closed water recirculating system. The system was equipped with the compact bioreactor using the plate gels capable of both nitrification and denitrification in a single unit. Ammonia and nitrite concentrations in the rearing water had been maintained below 0.05 mg-N/L, and nitrate concentration also controlled between 2 and 8 mg-N/L with the bioreactor. As concerns nitrogen budget in the closed system, 95.0% of nitrogen income from feed was lost as nitrogen gas from the closed system. All fish was alive for 91 days without any unusual behavior. Thus, the bioreactor performed both nitrification and denitrification abilities enough to rear the five fish for 91 days. The bioreactor using the plate gels would be effective to simplify the closed system both physically and operationally, since it can remove the ammonia excreted from fish as nitrogen gas by a single step.     

Ecology,thermodynamics and H.T. Odum's conjectures

The central rôle of energy in all life processes has led to the development of numerous hypotheses, conjectures and theories on the relationships between thermodynamics and ecological processes. In this paper we examine the theoretical and empirical support for these developments, and in particular for the widely published set of thermodynamic conjectures developed by H.T. Odum, in which the maximum power principle is put forward as a generic feature of evolution in ecosystems. Although they are widely used, we argue that many of the ecological studies that have adopted the ideas encapsulated in Odum's work have done so without being aware of some of the fundamental problems underlying this approach. We discuss alternative ways in which a general available-work concept could be constructed for use as a numeraire in an energy-centered ecological theory or paradigm. In so doing, we examine what is meant by material accessibility and energy stocks and flows with respect to traditional food web and food chain theories, and relate these to results from the evolutionary dynamics of ecosystems. We conclude that the various forms and uses of energy bound up in essential ecosystem processes present a formidable obstacle to obtaining an operational definition of a general, aggregated available-work concept, a prerequisite for the systems approach of Odum and others. We also show that the prototypical derivations of the maximum power principle, and its interpretation, are contradicted on many scales both by empirical data and models, thereby invalidating the maximum power principle as a general principle of ecological evolution. The conclusions point to the fundamental problem of trying to describe ecosystems in a framework which has a one-dimensional currency.     

A Spatial Analysis of Loop Closing Among Recycling,Remanufacturing, and Waste Treatment Firms in Texas

Industrial ecology has emerged as a key strategy for improving environmental conditions. A central element of industrial ecology is the concept of closing the loop in material use (cycling) by directing used material and products (wastes) back to production processes. This article examines the issue of geographic scale and loop closing for heterogeneous wastes through an analysis of the location and materials flows of a set of recycling, remanufacturing, recycling manufacturing, and waste treatment (RRWT) firms in Texas. The results suggest that there is no preferable scale at which loop closing should be organized. RRWT firms are ubiquitous and operate successfully throughout the settlement hierarchy. The cycling boundaries of RRWT firms are dependent primarily upon how and where their products are redirected to production processes rather than the firm's location in the settlement hierarchy. In other words, loop closing is dominated by the spatial economic logic of the transactions of the firm involved. These results suggest that we cannot assign loop closing to any particular spatial scale a priori nor can we conceive of closing the loop via RRWT firms in terms of monolithic networks bounded in space or place with internal material flows.     

Linkage reduction allows reconstitution of nucleosomes on DNA microdomains

We have established an experimental system for reconstitution of an individual nucleosome on a closed DNA microdomain (operationally defined as a DNA domain of a size so small as to be unable to establish titratable superhelical turns). The microdomain (185 base-pairs (bp), composed of 128 bp encompassing the central part of the Saccharomyces cerevisiae ADH II promoter plus 57 bp of a polylinker) was obtained by ligation under conditions that produced three circularized forms characterized by different linkage numbers. These linkomers were tested for nucleosome reconstitution with S. cerevisiae histones. It was observed that only microcircles with linkage reduction (delta Lk = 1 or 2) could form a nucleosome, as defined by protection of a 145(+/- 2) bp DNA fragment from micrococcal nuclease, relaxed forms (open or closed circles) could not.     

Exergy‐Based Population Dynamics

This article discusses whether “sustainability” has a physical meaning in applied thermodynamics. If it has, then it should be possible to derive general principles and rules for devising “sustainable systems.” If not, then other sides of the issue retain their relevance, but thermodynamic laws are not appropriate by themselves to decide whether a system or a scenario is sustainable. Here, we make use of a single axiom: that final consumption (material or immaterial) can be quantified solely in terms of equivalent primary exergy flows. On this basis, we develop a system theory that shows that if “simple” systems are based solely on the exploitation of fossil resources, they cannot be thermodynamically “sustainable.” But as renewable resources are brought into the picture and the system complexity grows, there are thresholds below or beyond which the system exhibits an ability to maintain itself (perhaps through fluctuations), in a self‐preserving (i.e., a sustainable) state. It appears that both complexity and the degree of nonlinearity of the transfer functions of the systems play a major role and—even for some of the simplest cases—lead to nontrivial solutions in phase space. Therefore, even if the examples presented in the article can be considered rather crude approximations to real, complex systems at best, the results show a trend that is worth further consideration.     

On the logical relationship between natural selection and self-organization

Most evolutionary biologists cherish Darwin's theory of natural selection (NS) as the process of adaptive evolution more than 140 years after publication of his first book on the subject. However, in the past few decades the study of self-organization (SO) in complex dynamical systems has suggested that adaptation may occur through intrinsic reorganization without NS. In this study, we attempt to describe the logical framework that relates the general process of SO to the specific process of NS. We describe NS as a mechanism that coordinates the coevolution of species in an ecosystem to effectively capture, process and dissipate solar energy into the earth's shadow. Finally, we conclude that NS is an emergent process founded on the same thermodynamic imperatives that are thought to underlie all SO. This perspective suggests that the theory of self-organizing systems offers a broader physical context in which to understand the process of NS, rather than contesting it. It even suggests the possibility that there may be a physical basis for understanding the origin of the process of NS. Rather than being merely a fluke of nature, the origin of NS that may be driven by energy flows across gradients.     

The Energetic Metabolism of Societies: Part II: Empirical Examples

Part I of this set of articles proposed methods to account for the energetic metabolism of societies. In this second part, the methods explicated in Part I are used to analyze the energy flows of societies with different "modes of subsistence": hunter-gatherers, a contemporary agricultural society in southeastern Asia, and a contemporary industrial society (Austria). The empirical examples are used to demonstrate differences in the "characteristic metabolism" of different modes of sub-sistence. The energy system of hunter-gatherers can be described as an "uncontrolled solar energy system," based mainly upon harvesting biomass without attending to its reproduction. Hunter-gatherers use only about 0.001% to 0.01% of the net primary production (NPP) of the territory they inhabit. Agricultural societies harness NPP to a much higher extent: Although agriculture often reduces NPP, the amount of biomass that agricultural societies use is much higher (about 20% of potential NPP). Because ecological energy flows are the main source of energy for agricultural societies, NPP strictly limits the energetic metabolism of agricultural societies. Industrial society uses area-independent energy sources (fossil and nuclear energy), which, however, result in new sustainability problems, such as greenhouse gas emissions. By providing methods to account for changes in energy flows, the metabolism approach proves itself to be a useful concept for analyzing society-environment interactions. The article demonstrates the difference between the metabolism approach and conventional energy statistics and discusses the significance of the proposed approach for sustainable development.