Rowena Ball

An environment far from equilibrium is thought to be a necessary condition for the origin and persistence of life. In this context we report open-flow simulations of a non-enzymic proto-metabolic system, in which hydrogen peroxide acts both as oxidant and driver of thermochemical cycling. We find that a Gaussian perturbed input produces a non-Boltzmann output fluctuation distribution around the mean oscillation maximum. Our main result is that net biosynthesis can occur under fluctuating cyclical but not steady drive. Consequently we may revise the necessary condition to "dynamically far from equilibrium".

In a major extension of previous work, we model the putative hydrothermal rock pore setting for the origin of life on Earth as a series of coupled continuous flow units (the toy train). Perfusing through this train are reactants that set up thermochemical and pH oscillations, and an activated nucleotide that produces monomer and dimer monophosphates. The dynamical equations that model this system are thermally self-consistent. In an innovative step that breaks some new ground, we build stochasticity of the inputs into the model. The computational results infer various constraints and conditions on, and insights into, chemical evolution and the origin of life and its physical setting: long, interconnected porous structures with longitudinal non-uniformity would have been favourable, and the ubiquitous pH dependences of biology may have been established in the prebiotic era. We demonstrate the important role of Gaussian fluctuations of the inputs in driving polymerization, evolution and diversification. In particular, we find that the probability distribution of the resulting output fluctuations is left-skewed and right-weighted (the loaded dice), which could favour chemical evolution towards a living RNA world. We tentatively name this distribution 'Goldilocks'. These results also vindicate the general approach of constructing and running a simple model to learn important new information about a complex system.

This paper presents and tests a previously unrecognised mechanism for driving a replicating molecular system on the prebiotic earth. It is proposed that cell-free RNA replication in the primordial soup may have been driven by self-sustained oscillatory thermochemical reactions. To test this hypothesis a well-characterised hydrogen peroxide oscillator was chosen as the driver and complementary RNA strands with known association and melting kinetics were used as the substrate. An open flow system model for the self-consistent, coupled evolution of the temperature and concentrations in a simple autocatalytic scheme is solved numerically, and it is shown that thermochemical cycling drives replication of the RNA strands. For the (justifiably realistic) values of parameters chosen for the simulated example system, the mean amount of replicant produced at steady state is 6.56 times the input amount, given a constant supply of substrate species. The spontaneous onset of sustained thermochemical oscillations via slowly drifting parameters is demonstrated, and a scheme is given for prebiotic production of complementary RNA strands on rock surfaces.

Article 27 of the Universal Declaration of Human Rights (1948) states that everyone has the right to freely share in scientific advancement and its benefits, and Article 15 of the International Covenant on Economic, Social and Cultural Rights (1966) recognizes the right of everyone to enjoy the benefits of scientific progress and its applications. Benefits include access to scientific and technological knowledge and opportunities for all to contribute to the scientific enterprise. I would add to these recognition of the scientific heritage of Indigenous peoples.
Yet in Australia, Indigenous people are under-represented in science education and research and in STEM (Science Technology Mathematics and Engineering) related careers, to an extent that could amount to a violation of human rights under Articles 27 and 15. In this article I deconstruct some of the myths and attitudes that may contribute to the perpetuation of this situation, and outline a way forward.

ABSTRACT The Hasegawa-Wakatani system of equations may be used to predict and study the behavior of plasma flow. Stability analysis of the flow requires results over prolonged time series, which places a great strain on computational resources. Results can only be achieved for a wide choice of parameters by using numerical methods that allow long time steps and do not pollute the results with numerical instabilities. The report presents an analysis of several linear multistep methods and concludes that much of the understanding of the stability of linear systems also applies to the study of nonlinear problems such as the Hasegawa-Wakatani system of equations. In particular, methods such as the backward differentiation formulas should be used with the stiff systems generated by the discrete formulation of the Hasegawa-Wakatani system of equations.

ABSTRACT A simple model for the thermal decomposition of amorphous cellulose is proposed that rationalizes the effect of water in promoting the charring process at the expense of volatilization. Simulations of mass-loss histories and product evolution are shown to be consistent with various experimental observations in the literature. Under char-promoting conditions where heat transfer is limited, anomalous thermal effects are predicted which indicate that char formation may not always be desirable in fire-inhibiting treatments of or strategies for cellulosic materials.

Vegetation fires release some fraction of the carbon in the biomass back to the atmosphere as CO2 and deposit some of the carbon onto the ground as charcoal, or pyrogenic carbon. It is an open, but not unanswerable, question as to whether the formation of pyrogenic carbon can effectively sequester carbon from atmospheric CO2. The purpose of this article is to conceptualise the question in terms of the global Charcoal Challenges, which deal with the scientific and socioeconomic questions associated with increasing the refractory (or long-term) black carbon pool at the expense of the atmospheric carbon pool, and to investigate the formation and decay of charcoal within this paradigm. Three particular Charcoal Challenges are examined: i) the feasibility of lowering atmospheric CO2 by biochar production, ii) the tension between na- ture’s use of fire to distribute carbon between long-term black carbon and short-term atmospheric pools and humans’ need to suppress fire, and iii) the premise that black carbon is a sink for CO2 only if its rate of formation exceeds its rate of decay, otherwise it is a source. It is shown how the thermal decomposition of cellulose, the major constituent of vegetation, during fires acts as a thermokinetic oscillator that regulates the global distribution of carbon between atmospheric and black carbon reservoirs. It is concluded that we cannot yet assume with certainty that the global black carbon reservoir is a carbon sink.

The most costly step in carbon capture from flue gas streams is regeneration of the pure CO2 stream from the sorbent, because of the high temperatures required by conventional systems. This work presents an entropy generation analysis of the new Endex calcium looping method, in which regeneration is driven directly by the heat of carbonation and pressure-swing is used to reduce the temperature of calcination. Entropy generation rates for the important subprocesses in the control volume are computed and visualised over the expedient parameter space. The performance of the system is optimised in two ways: by minimising the total entropy generation rate per mole of CO2 captured, and by maximising the capture efficiency. The tradeoff between these two objectives is highlighted.

In Endex coupling of reactive systems an exothermic reaction is directly coupled to an endothermic reaction. This work demonstrates the potential of Endex storage systems for safe storage of explosive and dangerous substances. Rigorous criteria are derived for which thermal runaway is forbidden in an Endex storage system, which is thus intrinsically safe. For several industrial organic peroxides that undergo exothermic thermal decomposition, endothermic reaction partners are chosen from hydrated metal salts that undergo endothermic dehydrations. Thermokinetic data from the literature are used to test Endex stabilization of these systems numerically. It is found that Endex stabilization is successful for periods of at least one week even when thermokinetic matching is not ideal. Some of the difficulties of Endex stabilization of peroxides thaat undergo multistage decomposition are highlighted.

Endex thermoreactive processes, in which an exothermic reaction is coupled thermokinetically to an endothermic reaction, in principle are more efficient than conventional processes. The purpose of this research is to quantify rigorously and in detail the thermodynamic efficiency advantage of an Endex calcium looping process for CO2 capture from flue gas streams, relative to a comparable conventional process, by entropy generation analysis. The theoretical background of second law analysis is reviewed, control volumes are defined and modelled, and the entropy generation rates are computed of all identified subprocesses. The Endex process is found to have superior relative second law efficiency by a factor of approximately 1.8, achieved mainly by a large reduction in the entropy penalty of regeneration at the expense of a modest increase in the entropy penalty of separation. The subprocesses most worthy (and unworthy) of optimization are identified. Results indicate that the Endex process is a promising candidate for thermal engineering optimization, because entropy generation is distributed relatively evenly across many subprocesses rather than concentrated in one or two.

Article 27 of the UN Universal Declaration of Human Rights (1948) states that everyone has the right freely to share in scientific advancement and its benefits, and Article 15 of the International Covenant on Economic, Social and Cultural Rights (1966) recognizes the right of everyone to enjoy the benefits of scientific progress and its applications. Benefits include access to scientific and technological knowledge and  opportunities for all to contribute to the scientific enterprise. I would add to these recognition of the scientific heritage of Indigenous peoples. Yet in Australia Aboriginal and Torres Strait Islander  peoples are under-represented in science education and research and in STEM (Science Technology Mathematics and Engineering) related careers, to an extent that could amount to a violation of human rights under Articles 27 and 15. In this article I deconstruct some of the myths and attitudes that may contribute to the perpetuation of this situation, and outline a way forward.

This document contains supplementary and supporting materials, including references, for ‘Second law analyses of Endex and conventional calcium looping processes for CO2 capture’, that are enriching but too distracting or lengthy to incorporate in the main article.

Endex thermoreactive processes, in which an exothermic reaction is coupled thermokinetically to an endothermic reaction, in principle are more efficient than conventional processes. The purpose of this research is to quantify rigorously and in detail the thermodynamic efficiency advantage of an Endex calcium looping process for CO2 capture from flue gas streams, relative to a comparable conventional process, by entropy generation analysis. The theoretical background of second law analysis is reviewed, control volumes are defined and modelled, and the entropy generation rates are computed of all identified subprocesses. The Endex process is found to have superior relative second law efficiency by a factor of approximately 2.7, achieved mainly by a large reduction in the entropy penalty of regeneration at the expense of a modest increase in the entropy penalty of separation. The subprocesses most worthy (and unworthy) of optimization are identified. Results indicate that the Endex process is a promising candidate for thermal engineering optimization, because entropy generation is distributed relatively evenly across many subprocesses rather than concentrated in one or two.

In an Endex reactor endothermic and exothermic reactions are directly thermally coupled and kinetically matched to achieve intrinsic thermal stability, efficient conversion, autothermal operation, and minimal heat losses. Applied to the problem of in-line carbon dioxide separation from flue gas, Endex principles hold out the promise of effecting a CO2-capture technology of unprecedented economic viability. In this work we describe an Endex Calcium Looping reactor, in which heat released by chemisorption of carbon dioxide onto calcium oxide is used directly to drive the reverse reaction, yielding a pure stream of CO2 for compression and geosequestration. In this initial study we model the proposed reactor as a continuous- flow dynamical system in the well-stirred limit, compute the steady states and analyse their stability properties over the operating parameter space, flag potential design and operational challenges, and sug- gest an optimum regime for effective operation.

Oscillatory thermal instabilities were well-known to chemical engineers from the mid 1950s to around the early 1990s, and a great many theory, modeling and experimental papers were published on the topic in the mainstream chemical engineering literature during that period. Yet since the 1990s there seems to have been a collective amnesia on thermochemical oscillations, and on stability analysis generally, among sectors of the chemical engineering community which deal with reactive thermal hazards and runaway criteria. In this case ignorance is dangerous. This contribution highlights the importance of mathematical stability analysis and corrects certain misconceptions in the current literature regarding thermal stability criteria. Two recently published systems in which stability analysis was ignored are examined, revealing oscillatory instabilities of dangerous amplitude that cannot be detected using classical (Semenov) ignition theory. Some informed conjectures on how this state of affairs arose may point the way to improvements in reactive process safety. It is also suggested that oscillatory thermal instability may be usefully exploited.

We analyse a simplified dynamical model that emulates the overall process of self-assembly of amphiphilic molecules into micelles under non-equilibrium conditions. The study is motivated by a review of experimental evidence in the literature for the occurrence of bistability and ...

... R. Ball RL Dewar Research School of Physical Sciences & Engineering The Australian National University, Canberra ACT 0200 Australia e-mail Rowena.Ball@anu.edu.au, Robert.Dewar@anu. edu.au H. Sugama National Institute For Fusion Science Oroshi-cho, Toki GIFU 509 ...

... Mathematical Sciences Institute, The Australian National University, Canberra 0200 Australia. E-mail Rowena.Ball@anu.edu.au † Institute for Fusion Studies, The University of Texas at Austin, Austin, TX 78712 USA. E-mail horton@physics.utexas.edu. Abstract. ...

Publikationsansicht. 36106271. Endothermal stabilization of chemical reactors (1996). Ball,Rowena. Abstract. Bibliography: p. 169-177. Details der Publikation. Archiv, NDLTD Union Catalog (United States). Keywords, Chemical reactors Mathematical models, Stability. ...

Abstract A case study in bifurcation and stability analysis is presented, in which reduced dy-namical system modelling yields substantial new global and predictive information about the behaviour of a complex system. The first smooth pathway, free of pathological and persistent ...

When I began studying science as an undergraduate, and over the years since as a postgraduate student and postdoctoral researcher, people often commented that the choice of science was an unconventional, and in some sense, pioneering vocation for a woman. This was ...

The classical pitchfork of singularity theory is a twice-degenerate bifurcation that typically occurs in dynamical system models exhibiting Z_2 symmetry. Non-classical pitchfork singularities also occur in many non-symmetric systems, where the total bifurcation environment is usually more complex. In this paper three-dimensional manifolds of critical points, or limit-point shells, are introduced by examining several bifurcation problems that contain a pitchfork as an organizing centre. Comparison of these surfaces shows that notionally equivalent problems can have significant positional differences in their bifurcation behaviour. As a consequence, the parameter range of jump, hysteresis, or phase transition phenomena in dynamical models (and the physical systems they purport to represent) is determined by other singularities that shape the limit-point shell.

Extra, extra, read all about it! February edition of the internationally renowned Gulflander Gazette! Floods past, floods present, and floods of nostalgia! Freight movement on the Normanton-Croydon line! Plus, a special report from our Foreign Correspondent!