A critical assessment of scientific retroduction

We analyse Peirce's original idea concerning abduction from the perspective of a critical philosophy, the same philosophy in Peirce's background. Peirce's realism is directly related to reason and experience and has ties with the idea of abstraction. We show how the philosophical environment of science abruptly changed, specially for physics, in the last period of the XIX century and the initial period of the XX century, when science was divided in disciplines and set free from the control of philosophy. The phenotype of the physicist changed from abstract into imaginative thinker. Further, abstraction was linked to metaphysics and attacked as such. Elements of phantasy and dogmatism entered the scene in place of abstraction alongside ideas taken from the observable world. We provide evidence that the scientists of the newer kind had problems understanding those of the older school. As a consequence of the problems arisen in conciliating the idea of science grounded in experience and reason with the science actually practised, the former conceptualisation was abandoned. Abduction was then expelled from science. In the late part of the XX century and the early part of our century abduction re-emerged but without its scientific attributes. Influenced by a constructivist, Piagetian, perspective of science, we propose and discuss a small number of conditions that we identify as characteristics of rational abduction: rules for the rational construction of theories. We show how a classical example of belief that satisfies today's most common definition of abduction does not match the standards of scientific retroduction. We further show how the same rules indicate the detachment of Special Relativity from the observable world, a fact actually known to Einstein. Finally, the same rules indicate the initial point in the path to re-conciliate Electromagnetism with the classical view of spatial relations, a matter not possible for the imaginative scientist but not extremely difficult for the abstract scientist. We close arguing that there is an urgent need to develop a critical epistemology, and to give room in science for the abstract scientist

Dental Health and Mortality in People With End-Stage Kidney Disease Treated With Hemodialysis: A Multinational Cohort Study

Background Dental disease is more extensive in adults with chronic kidney disease, but whether dental health and behaviors are associated with survival in the setting of hemodialysis is unknown. Study Design Prospective multinational cohort. Setting & Participants 4,205 adults treated with long-term hemodialysis, 2010 to 2012 (Oral Diseases in Hemodialysis [ORAL-D] Study). Predictors Dental health as assessed by a standardized dental examination using World Health Organization guidelines and personal oral care, including edentulousness; decayed, missing, and filled teeth index; teeth brushing and flossing; and dental health consultation. Outcomes All-cause and cardiovascular mortality at 12 months after dental assessment. Measurements Multivariable-adjusted Cox proportional hazards regression models fitted with shared frailty to account for clustering of mortality risk within countries. Results During a mean follow-up of 22.1 months, 942 deaths occurred, including 477 cardiovascular deaths. Edentulousness (adjusted HR, 1.29; 95% CI, 1.10-1.51) and decayed, missing, or filled teeth score ≥ 14 (adjusted HR, 1.70; 95% CI, 1.33-2.17) were associated with early all-cause mortality, while dental flossing, using mouthwash, brushing teeth daily, spending at least 2 minutes on oral hygiene daily, changing a toothbrush at least every 3 months, and visiting a dentist within the past 6 months (adjusted HRs of 0.52 [95% CI, 0.32-0.85], 0.79 [95% CI, 0.64-0.97], 0.76 [95% CI, 0.58-0.99], 0.84 [95% CI, 0.71-0.99], 0.79 [95% CI, 0.65-0.95], and 0.79 [95% CI, 0.65-0.96], respectively) were associated with better survival. Results for cardiovascular mortality were similar. Limitations Convenience sample of clinics. Conclusions In adults treated with hemodialysis, poorer dental health was associated with early death, whereas preventive dental health practices were associated with longer survival

Braids on the poincaré section: A laser example

Fil:Solari, H.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Natiello, M.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Vázquez, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

La ciencia administrada

An understanding and use of science subordinate to the production process extends worldwide, starting from USAaround the end of World War II. This strategy determines the advance of a management process for research and training on the scientific field, operated by the National administrations and, through them, by the productive apparatus. Such subordination of scientific activity to productive use promotes the extinction of critical thinking in favor of a purely instrumental thinking and thus the suffocation of criticism and creativity in favor of the exploitation of existing science: normal science. In training, a shift takes place, from training designed to cultivate rationality and critical examination, valuing knowledge as a good in itself, to a training designed to promote the uncritical acceptance of normal science, its use and "enhancement" in a merely professional way, valuing knowledge only insofar as it is useful from a commercial or a security point of view. This shift is reproduced in an almost coercive manner by the methods of evaluation and the publishing policies that punish critic and creative researchers while systematically rewarding repetition, technical use and instrumental subordination to the parameters of normal science. This managing mechanism tends to enhance the reproduction of its traits and to push towards extinction those traits that fail to match its goals.A partir del fin de la Segunda Guerra Mundial se extiende, partiendo de los EEUU, una comprensión y uso de la ciencia subordinadas al proceso de producción. Esto determina el avance, sobre el campo científico, de un proceso de administración de la investigación y de la formación por parte del Estado y, a través de él, del aparato productivo. Esa subordinación de la actividad científica a la utilidad productiva promueve la extinción del pensamiento crítico en favor de un pensamiento puramente instrumental. Y con ello el sofocamiento de la crítica y la creación en favor de la explotación de la ciencia existente: la ciencia normal. En la formación, se pasa de una formación destina-da a cultivar la racionalidad y el examen crítico, valorando el conocimiento como un bien en sí mismo, a una formación destinada a promover la aceptación acrítica de la ciencia normal y su uso y “acrecentamiento” meramente profesionales, valorando el cono-cimiento sólo en la medida en que es útil desde el punto de vista mercantil o de segu-ridad. Todo ello, reproducido de modo casi coactivo por los métodos de evaluación y las políticas de publicación, que castigan a los investigadores críticos y creativos y premian sistemáticamente la repetición, el uso técnico y la subordinación instrumental a los paráme-tros de la ciencia normal. Estos mecanismos tienden a ampliar la reproducción de estos rasgos y a empujar a la extinción aquellos que no se ajustan a sus objetivos

Pulse bifurcation and transition to spatiotemporal chaos in an excitable reaction-diffusion model

We address the stability of solitary pulses as well as some other traveling structures near the onset of spatiotemporal chaos in a two-species reaction-diffusion model describing the oxidation of CO on a Pt(1 1 0) surface in one spatial dimension. First, the boundary of the existence region of stable pulses is explored by means of numerical integration of the reaction-diffusion equations. The partial differential equations (PDEs) of the model are next reduced to a set of ordinary differential equations (ODEs) by the introduction of a moving frame and a detailed analysis of traveling wave solutions and their bifurcations is presented. The results are then compared to findings in numerical simulations and stability computations in the full PDE. The solutions of the ODE are organized around a codimension-2 global bifurcation from which two branches of homoclinic orbits corresponding to solitary pulse solutions in the PDE originate. This bifurcation mediates a change in the dynamics of the excitable medium, as seen in numerical simulations, from a regime dominated by stable pulses and wavetrains traveling with constant shape and speed to spatiotemporally chaotic dynamics. We also find a branch of heteroclinic orbits corresponding to fronts in the PDE. Even though these fronts are found to be unstable for the PDE, their spatial signature is frequently observed locally as part of the spatiotemporally chaotic profiles obtained by direct numerical simulation

Topological analysis of chaotic time series data from the Belousov-Zhabotinskii reaction

Summary. We have applied topological methods to analyze chaotic time series data from the Belousov-Zhabotinskii reaction. First, the periodic orbits shadowed by the data set were identified. Next, a three-dimensional embedding without selfintersections was constructed from the data set. The topological structure of that flow was visualized by constructing a branched manifold such that every periodic orbit in the flow could be held by the branched manifold. The branched manifold, or induced template, was computed using the three lowest-period orbits. The organization of the higher-period orbits predicted by this induced template was compared with the organization of the orbits reconstructed from the data set with excellent results. The consequences of the presence of certain knots found in the data are discussed