The emergence of environmental homeostasis in complex ecosystems

The Earth, with its core-driven magnetic field, convective mantle, mobile lid tectonics, oceans of liquid water, dynamic climate and abundant life is arguably the most complex system in the known universe. This system has exhibited stability in the sense of, bar a number of notable exceptions, surface temperature remaining within the bounds required for liquid water and so a significant biosphere. Explanations for this range from anthropic principles in which the Earth was essentially lucky, to homeostatic Gaia in which the abiotic and biotic components of the Earth system self-organise into homeostatic states that are robust to a wide range of external perturbations. Here we present results from a conceptual model that demonstrates the emergence of homeostasis as a consequence of the feedback loop operating between life and its environment. Formulating the model in terms of Gaussian processes allows the development of novel computational methods in order to provide solutions. We find that the stability of this system will typically increase then remain constant with an increase in biological diversity and that the number of attractors within the phase space exponentially increases with the number of environmental variables while the probability of the system being in an attractor that lies within prescribed boundaries decreases approximately linearly. We argue that the cybernetic concept of rein control provides insights into how this model system, and potentially any system that is comprised of biological to environmental feedback loops, self-organises into homeostatic states

Tipping points in complex coupled life-environment systems

Simple models of complex phenomena provide powerful insights and suggest low-level mechanistic descriptions. The Earth system arises from the interaction of subsystems with multi-scale temporal and spatial variability; from the microbial to continental scales, operating over the course of days to geological time. System-level homeostasis has been demonstrated in a number of conceptual, artificial life, models which share the advantage of a thorough and transparent analysis. We reintroduce a general model for a coupled life-environment model, concentrating on a minimal set of assumptions, and explore the consequences of interaction between simple life elements and their shared, multidimensional environment. In particular stability, criticality and transitions are of great relevance to understanding the history, and future of the Earth system. The model is shown to share salient features with other abstract systems such as Ashby's Homeostat and Watson and Lovelock's Daisyworld. Our generic description is free to explore high-dimensional, complex environments, and in doing so we show that even a small increase in the environmental complexity gives rise to very complex attractor landscapes which require a much richer conception of critical transitions and hysteresi

"Almost-stable" matchings in the Hospitals / Residents problem with Couples

The Hospitals / Residents problem with Couples (hrc) models the allocation of intending junior doctors to hospitals where couples are allowed to submit joint preference lists over pairs of (typically geographically close) hospitals. It is known that a stable matching need not exist, so we consider min bp hrc, the problem of finding a matching that admits the minimum number of blocking pairs (i.e., is “as stable as possible”). We show that this problem is NP-hard and difficult to approximate even in the highly restricted case that each couple finds only one hospital pair acceptable. However if we further assume that the preference list of each single resident and hospital is of length at most 2, we give a polynomial-time algorithm for this case. We then present the first Integer Programming (IP) and Constraint Programming (CP) models for min bp hrc. Finally, we discuss an empirical evaluation of these models applied to randomly-generated instances of min bp hrc. We find that on average, the CP model is about 1.15 times faster than the IP model, and when presolving is applied to the CP model, it is on average 8.14 times faster. We further observe that the number of blocking pairs admitted by a solution is very small, i.e., usually at most 1, and never more than 2, for the (28,000) instances considered

Les effets pervers d’une bonne idée : la démocratie directe en Californie

La démocratie directe a vu le jour en Californie au début du XXe siècle dans la foulée du mouvement progressiste, issu d’un profond désabusement face aux institutions du gouvernement représentatif. En ce sens, elle peut apparaître à plusieurs comme une solution aux problèmes du même genre qui se posent au Québec et au Canada de nos jours. Cependant, l’initiative populaire et le référendum californiens ont engendré des effets inattendus qui, selon plusieurs observateurs, sont à l’opposé de ceux que recherchaient leurs promoteurs. Le débat qu’ils suscitent oblige tout participant à clarifier ses valeurs.Direct democracy appeared in California at the beginning of the century in the wake of widespread disillusionment with representative democracy and the Progressive movement. It might provide an answer to similar problems encountered in Quebec and Canada today. However, the initiative and the referendum in California have had such important, unintended consequences that many observers declare them to have changed into the opposite of what their creators intended. The debate these institutions evoke requires a clarification of its underlying values

La gestion du personnel dans les ministères du gouvernement du Québec

Cette étude porte sur la situation et les pratiques des services de personnel dans les ministères du gouvernement du Québec en 1972 telles que décrites par les responsables eux-mêmes.The point of departure of this study in the observation that personnel management in government departments receives much less study than do the activities of central management and control agencies. In Quebec, the history of recent: reforms had dealt above all with the creation of the Civil Service Commission (1965), the Civil Service Department (1969) and the Treasury Board (1970). The Treasury Board acts for the Executive Council (Cabinet) in matters dealing with organization, establishment, working conditions and general administrative policy. The Civil Service Department has two main functions, to negociate contracts with civil servants' associations and to elaborate and coordinate government personnel policy. The Civil Service Commission has the usual role of guardian of the merit system ; it also has responsibility for the classification plan.The working hypothesis of this study is that government departments retain all personnel management tasks which have not been assumed by central management and control agencies. In order to try to test this hypothesis a questionnaire was sent, in the summer of 1972, to the directors of personnel in all Quebec government departments except the Civil Service Department. In all, written replies covering some fifteen departments were received, as well as some verbal comments in the course of interviews. The results give the impressions of the directors of personnel in the departments concerned. No additional research has yet been con-ducted to test these impressions against actual practice. This would be desirable for it is likely that both the central agencies and the department personnel officers have some impressions which are not supported by the facts.In terms of overall impressions it was found that the Treasury Board and the Department of Finance were viewed by the great majority as countrol agencies. The Civil Service Department and the Civil Service Commission were viewed as agencies of both control and service, a reputation which is somewhat surprising in the case of the Commission.Over the entire range of personnel activities, the personnel directors report considerable initiative which falls to them. The classification framework is prepared by the Civil Service Commission but the classifying of positions is mainly done by the departments. Likewise, the departments must do their own planning for manpower requirements subject to Treasury Board approval. In competitions fornew appointments or for promotions, they provide the majority of the members of examining boards, under Civil Service Commission supervision. The Commission delegates a varying amount of authority to the departments in these matters but it always verifies the application of the law and the classification requirements. Each department alos must develop its own training programme within the general policy established by the Civil Service Department. Over the entire field of staffing procedures and practices, it appears that most departments do not as yet have thorough evaluation procedures to verify the degree of success or failure of these procedures and practices.With respect to labour relations, the departments are mainly involved with the application, not the negociation, of collective bargaining agreements. The main control of this application comes through the grievance procedure. If a grievance cannot be settled within a department, it then goes to arbitration. At this stage the employer's side is represented by the General Directorate of the Civil Service Department (DGRT) ; the personnel service of the department where the grievance originated acts as adviser to the DGRT.On the subject of occasional and contractual employees, all departments are governed by the regulations issued by the Civil Service Commission (in the case of occasional employees) or by the Treasury Board (in the case of contractual employees). The departments have considerable freedom in these cases because there are no permanent positions involved, no Civil Service Commission competitions and no fixed rules about wages etc., other than the going rates for similar jobs.In conclusion, the replies to the questionnaires support the hypothesis of a considerable residue of departmental responsibility in personnel administration. In fact, the growth of central agency activity requires increased activity and competency at the departmental level. The Quebec Government has recognized the importance of the departmental directors of personnel by the creation of the Advisory Committee of Personnel Managers, which reports to all three central agencies.Another conclusion to the study is that the Civil Service Department, while it has established itself as a service agency in the eyes of the other departments, does not appear to have overcome the problem of the dispersal of decision centers as it was supposed to do. One reason for this is the coexistence of the merit system, with the powers it entails for the Civil Service Commission, and the collective bargaining system, with its own structures for policy making and the arbitration of grievances