The construction of Electromagnetism

Abstract We examine the construction of electromagnetism in its current form, and in an alternative form, from a point of view that combines a minimal realism with strict rational demands. We begin by discussing the requests of reason when constructing a theory and next, we follow the historical development as presented in the record of original publications, the underlying epistemology (often explained by the authors) and the mathematical constructions. The historical construction develops along socio-political disputes (mainly, the reunification of Germany and the second industrial revolution), epistemic disputes (at least two demarcations of science in conflict) and several theories of electromagnetism. Such disputes resulted in the militant adoption of the ether by some, a position that expanded in parallel with the expansion of Prussia. This way of thinking was facilitated by the earlier adoption of a standpoint that required, as a condition for understanding, the use of physical hypothesis in the form of analogies; an attitude that is antithetic to Newton's “hypotheses non fingo”. While the material ether was finally abandoned, the epistemology survived in the form of “substantialism” and a metaphysical ether: the space. The militants of the ether attributed certainties regarding the ether to Faraday and Maxwell, when they only expressed doubts and curiosity. Thus, the official story is not the real history. This was achieved by the operation of detaching Maxwell's electromagnetism from its construction and introducing a new game of formulae and interpretations. Large and important parts of Maxwell work are today not known, as for example, the rules for the transformation of the electromagnetic potentials between moving systems. When experiments showed that all the theories based in the material ether were incorrect, a new interpretation was offered: Special Relativity (SR). At the end of the transformation period a pragmatic view of science, well adapted to the industrial society, had emerged, as well as a new protagonist: the theoretical physicist. The rival theory of delayed action at distance initiated under the influence of Gauss was forgotten in the midst of the intellectual warfare. The theory is indistinguishable in formulae from Maxwell's and its earlier versions are the departing point of Maxwell for the construction of his equations. We show in a mathematical appendix that such (relational) theory can incorporate Lorentz' contributions as well as Maxwell's transformations and C. Neumann's action, without resource to the ether. Demarcation criteria was further changed at the end of the period making room for habits and intuitions. When these intuited criteria are examined by critical reason (seeking for the fundaments) they can be sharpened with the use of the Non Arbitrariness Principle, which throws light over the arbitrariness in the construction of SR. Under a fully rational view SR is not acceptable, it requires to adopt a less demanding epistemology that detaches the concept from the conception, such as Einstein's own view in this respect, inherited from Hertz. In conclusion: we have shown in this relevant exercise how the reality we accept depends on earlier, irrational, decisions that are not offered for examination but rather are inherited from the culture

A mathematically assisted reconstruction of the initial focus of the yellow fever outbreak in Buenos Aires (1871)

We discuss the historic mortality record corresponding to the initial focus of the yellow fever epidemic outbreak registered in Buenos Aires during the year 1871 as compared to simulations of a stochastic population dynamics model. This model incorporates the biology of the urban vector of yellow fever, the mosquito Aedes aegypti, the stages of the disease in the human being as well as the spatial extension of the epidemic outbreak. After introducing the historical context and the restrictions it puts on initial conditions and ecological parameters, we discuss the general features of the simulation and the dependence on initial conditions and available sites for breeding the vector. We discuss the sensitivity, to the free parameters, of statistical estimators such as: final death toll, day of the year when the outbreak reached half the total mortality and the normalized daily mortality, showing some striking regularities. The model is precise and accurate enough to discuss the truthfulness of the presently accepted historic discussions of the epidemic causes, showing that there are more likely scenarios for the historic facts.Comment: 25 pages, 12 figure

Algas epífitas indicadoras de calidad del agua en arroyos vinculados a la Laguna de Los Padres

Fil: Esquiús, K.S.. Laboratorio de Limnología, Departamento de Biología, FCEyN, UNMdPFil: Escalante, Alicia H.. Laboratorio de Limnología, Departamento de Biología, FCEyN, UNMdPFil: Solari, Lía Cristina. Instituto de Limnología Dr. R. Ringuelet, (ILPLA), CONICET-UNLP. Florencio Varela, Argentin

Wind Tunnel Experimentation on Stationary Downbursts at WindEEE Dome

In the context of the European Project THUNDERR a scientific collaboration between the Wind Engineering and Structural Dynamics (Windyn) Research Group of the University of Genoa (Italy) and the Wind Engineering, Energy and Environment (WindEEE) Research Institute of Western University (Canada) has been established to study experimentally at the WindEEE Dome facility how the main geometrical and mechanical properties of downbursts are affected by different cloud base outflows of stationary thunderstorms. At present, the analysis of the downbursts simulated experimentally is ongoing and some preliminary elaborations have been obtained concerning the qualitative and quantitative interpretation of the corresponding signals. Classical signal decomposition was applied to experimentally produced downbursts in the WindEEE Dome in order to study transient features of the time series. This study presents the results for two radial positions from downdraft centre and for twenty repetitions per radial position. Several prospects for further research are also discussed

A novel approach to scaling experimentally produced downburst-like impinging jet outflows

Downbursts are intense thunderstorm winds that can be found in most, if not all, regions around the globe. An accurate experimental investigation of downburst winds requires the proper geometric and kinematic scaling between the model downburst (m) created in a wind simulator and the full scale downburst event (p). This study makes a threefold contribution to further understanding of downburst outflows. First, the article introduces a new scaling methodology for downburst outflows based on the signal decomposition techniques of p and m downburst wind records. Second, the study describes a large set of m downbursts produced in the WindEEE Dome simulator at Western University and critically discusses their similarity with a large set of p events detected in the Mediterranean. Third, using the proposed scaling methodology, this paper attempts to partially reconstruct two p downburst events recorded in Genoa and Livorno, Italy. In total, 17 p and 1400 m downburst outflows are investigated herein, which represents the largest database of p and m downbursts combined. The similarity between p and m downbursts is quantitatively demonstrated for both mean and fluctuating components of the flows. The scaling method is verified by accurately predicting the known anemometer height of p events using m downburst measurements

Identification of virulence markers in clinically relevant strains of Acinetobacter genospecies

Nine Acinetobacter strains from patients and hospital environment were analyzed for virulence markers, quorum sensing signal production, and the presence of luxI and luxR genes. The strains had several properties in common: growth in iron limited condition, biofilm formation, and no active protease secretion. Significantly higher catechol production was determined in patient isolates (P < 0.03), but other invasiveness markers, such as lipase secretion, amount of biofilm, cell motility, antibiotic resistance, and hemolysin production, showed large variability. Notably, all members of the so-called A. calcoaceticus-A. baumannii complex, regardless of whether the source was a patient or environmental, secreted medium to long-chain N-acyl homoserine lactones (AHL) and showed blue light inhibition of cell motility. In these strains, a luxI homologue with a homoserine lactone synthase domain and a luxR putative regulator displaying the typical AHL binding domain were identified

Science, dualities and the phenomenological map

We present an epistemological scheme of natural sciences inspired in Peirce's pragmaticist view, stressing the role of the \emph{phenomenological map}, that connects reality and our ideas about it. The scheme has a recognisable mathematical/logical structure which allows to explore some of its consequences. We show that seemingly independent principles as the requirement of reproducibility of experiments and the Principle of sufficient reason are both implied by the scheme, as well as Popper's concept of falsifiability. We show that the scheme has some power in demarcating science by first comparing with an alternative scheme advanced during the first part of the XX century (which we call Popper-Einstein and has its roots in Hertz). Further, the identified differences allow us to focus in the construction of Special Relativity showing that it uses an intuited concept of velocity that does not satisfy the requirements of reality in Peirce. We track the problem to hidden hypothesis in Einstein's work. While the main mathematical observation has been known for more than a century it has not been investigated from an epistemological point of view, probably because the socially dominating epistemology in physics discourages so doing

Nonlinear Interaction of Transversal Modes in a CO2 Laser

We show the possibility of achieving experimentally a Takens-Bogdanov bifurcation for the nonlinear interaction of two transverse modes ($l = \pm 1$) in a $CO_2$ laser. The system has a basic O(2) symmetry which is perturbed by some symmetry-breaking effects that still preserve the $Z_2$ symmetry. The pattern dynamics near this codimension two bifurcation under such symmetries is described. This dynamics changes drastically when the laser properties are modified.Comment: 16 pages, 0 figure