‘Das politische Welträtsel’: Ernst Haeckel en het Duitse liberalisme 1859-1900’

Het werk van de evolutionair-morfoloog en wetenschapspopularisator Ernst Haeckel is uiterst omstreden. Zijn sociaaldarwinisme is na de Tweede Wereldoorlog om begrijpelijke redenen in een kwaad daglicht komen te staan. De meest expliciete veroordeling van Haeckel is waarschijnlijk Daniel Gasmans The Scientific Origins of National Socialism in Ernst Haeckel. Inmiddels hebben wetenschapshistorici het eenzijdig negatieve beeld genuanceerd. Volgens de standaardkritiek is het anachronistisch om latere ontwikkelingen terug te projecteren op het werk van Haeckel. Zo ziet Robert Richards in Haeckel geen voorloper van het nazisme, maar een late vertegenwoordiger van een Duitse romantische traditie, die teruggaat op Alexander von Humboldt en Goethe. Met andere woorden Richards is meer geïnteresseerd in de intellectuele achtergronden, dan in de politieke en culturele werking van Haeckels denken

Wetenschapsgeschiedenis op lange termijn: flexibiliteit en fragiliteit van disciplines

  Long-term history of science: on the flexibility and fragility of scientific disciplinesMost scientific disciplines, such as chemistry, biology and physics, are now about two centuries old. Using physics as a case study the present paper aims to account for this longevity. What kept the physics discipline together from the early nineteenth century onwards? Literature on the rise of physics suggests that the discipline was formed around energy, the ether, or other theoretical notions. Yet the twentieth-century revolutions in physics showed that the discipline could prosper without some of its most 'fundamental' concepts. Some scholars conclude that internal factors are therefore irrelevant and disciplinary identity and continuity are purely institutional. Drawing on the work of Thomas Kuhn, Peter Galison and Andrew Warwick, this paper defends a different point of view. Although there is no intellectual core of disciplines, the prolonged existence of disciplines cannot be explained without some degree of internal continuity. If there is a revolution of a theoretical level, there may still be continuity on the level of experimental practices (and vice versa). It is this flexibility that accounts for the fact that disciplines may adapt to different circumstances. In addition, an educational tradition is required to transmit knowledge from one generation to the next

Statistical models of diffusion and aggregation for coke formation in a catalyst pore

We simulated models of diffusion and aggregation in long pores of small widths in order to represent the basic mechanisms of coke deposition in catalysts' pores. Coke precursors are represented by particles injected at the pore entrance. Knudsen diffusion, which is usually expected inside the pores, is modeled by ballistic motion of those particles. The regime of molecular diffusion is also analyzed via models of lattice random walks biased along the pores. The aggregation at the surface or near previously aggregated particles was modeled by different probabilistic rules, accounting for the possibilities of more compact or more ramified deposits. In the model of Knudsen diffusion and in some cases of molecular diffusion, there is an initial regime of uniform deposition along the pore, after which the deposits acquire an approximately wedge shape, with the pore plugging near its entrance. After the regime of uniform deposition and before that of critical pore plugging, the average aggregation position slowly decreases with the number N of deposited particles approximately as N^{-0.25}. The apparently universal features of deposits generated by microscopic models are compared with those currently adopted in continuum models.Comment: 14 pages (figures included), to appear in Physica

Etude de la croissance relative chez l’escargot Limicolaria flammea (Muller,1774), soumis a deux types de regimes alimentaires

Des naissains de Limicolaria flammea au nombre de 200 ont été soumis à deux types de régimes. Cent d’entre eux ont été nourris avec un mélange de feuilles de Carica papaya (Caricaceae), feuilles de manioc Manihot esculenta tandis que les 100 autres ont été nourris avec un aliment à base de concentré. L’objectif est de comparer les deux types d’aliments et de déterminer le régime alimentaire induisant les meilleures performances biologiques. Chaque mois, 20 escargots de chaque lot sont conduits au laboratoire pour la détermination des paramètres métriques à savoir le poids vif des sujets, la longueur, la largeur et la hauteur des coquilles. Les régimes concentrés ont donné de meilleurs résultats de croissance pondéralepar rapport aux régimes à base de végétaux. La relation existante entre le poids et la largeur est très faible chez les escargots nourris à base de concentré mais le contraire se produit chez les sujets consommateurs d’un mélange de feuilles de végétaux. Qu’ils soient nourris avec un mélange de feuilles de végétaux ou avec un aliment composé, le poids augmente plus vite que la hauteur. Ainsi le régime alimentaire induisant les meilleures performances de croissance pondérale et coquillère et un faible taux de mortalité cumulée est le régime concentré. Mots clés: Limicolaria flammea, naissains, régimes alimentaires English Title: Study of the relative growth in Limicolaria flammea snail (Muller,1774), subjected to two types of diets English Abstract A number of 200 Limicolaria flammea spats have been subjected to two types of diets. One hundred of them were fed on a mixture of Carica papaya leaves (Caricaceae), Manihot esculenta cassava, while the other 100 were fed on concentrate feed. The goal is to compare the two types of foods and determine the diet that induces the best biological performance. Each month, 20 snails of each batch are taken to the laboratory to determine the metric parameters, namely individuals live weight, the length, the width and the height of the shells. Concentrate diets gave better weight growth results compared to plant-based diets. The existing relation ship between weight and width is very low in concentrate-fed snails, but the opposite occurs in individuals consuming a mixture of plant leaves. Whether they are fed with a mixture of plant leaves or with a compound feed, the weight increases faster than the height. So the diet with the best weight and shell growth performance and a cumulative low mortality rate is the concentrate diet. Keywords: Limicolaria flammea, spat, diet

Roughness fluctuations, roughness exponents and the universality class of ballistic deposition

In order to estimate roughness exponents of interface growth models, we propose the calculation of effective exponents from the roughness fluctuation (sigma) in the steady state. We compare the finite-size behavior of these exponents and the ones calculated from the average roughness for two models in the 2+1-dimensional Kardar-Parisi-Zhang (KPZ) class and for a model in the 1+1-dimensional Villain-Lai-Das Sarma (VLDS) class. The values obtained from sigma provide consistent asymptotic estimates, eventually with smaller finite-size corrections. For the VLDS (nonlinear molecular beam epitaxy) class, we obtain alpha=0.93+-0.01, improving previous estimates. We also apply this method to two versions of the ballistic deposition model in two-dimensional substrates, in order to clarify the controversy on its universality class raised by numerical results and a recent derivation of its continuous equation. Effective exponents calculated from sigma suggest that both versions are in the KPZ class. Additional support to this conclusion is obtained by a comparison of the full roughness distributions of those models and the distribution of other discrete KPZ models.Comment: 12 pages (4 figures included); to be published in Physica

Universality in two-dimensional Kardar-Parisi-Zhang growth

We analyze simulations results of a model proposed for etching of a crystalline solid and results of other discrete models in the 2+1-dimensional Kardar-Parisi-Zhang (KPZ) class. In the steady states, the moments W_n of orders n=2,3,4 of the heights distribution are estimated. Results for the etching model, the ballistic deposition (BD) model and the temperature-dependent body-centered restricted solid-on-solid model (BCSOS) suggest the universality of the absolute value of the skewness S = W_3 / (W_2)^(3/2) and of the value of the kurtosis Q = W_4 / (W_2)^2 - 3. The sign of the skewness is the same of the parameter \lambda of the KPZ equation which represents the process in the continuum limit. The best numerical estimates, obtained from the etching model, are |S| = 0.26 +- 0.01 and Q = 0.134 +- 0.015. For this model, the roughness exponent \alpha = 0.383 +- 0.008 is obtained, accounting for a constant correction term (intrinsic width) in the scaling of the squared interface width. This value is slightly below previous estimates of extensive simulations and rules out the proposal of the exact value \alpha=2/5. The conclusion is supported by results for the ballistic deposition model. Independent estimates of the dynamical exponent and of the growth exponent are 1.605 <= z <= 1.64 and \beta = 0.229 +- 0.005, respectively, which are consistent with the relations \alpha + z = 2 and z = \alpha / \beta.Comment: 8 pages, 9 figures, to be published in Phys. Rev.

Wigner Surmise For Domain Systems

In random matrix theory, the spacing distribution functions $p^{(n)}(s)$ are well fitted by the Wigner surmise and its generalizations. In this approximation the spacing functions are completely described by the behavior of the exact functions in the limits s->0 and s->infinity. Most non equilibrium systems do not have analytical solutions for the spacing distribution and correlation functions. Because of that, we explore the possibility to use the Wigner surmise approximation in these systems. We found that this approximation provides a first approach to the statistical behavior of complex systems, in particular we use it to find an analytical approximation to the nearest neighbor distribution of the annihilation random walk

Island coarsening in one-dimensional models with partially and completely reversible aggregation

Using computer simulations and scaling ideas, we study one-dimensional models of diffusion, aggregation and detachment of particles from islands in the post-deposition regime, i. e. without flux. The diffusion of isolated particles takes place with unit rate, aggregation occurs immediately upon contact with another particle or island, and detachment from an island occurs with rate epsilon = exp(-E/kT), where E is the related energy barrier. In the partially reversible model, dissociation is limited to islands of size larger than a critical value i, while in the completely reversible model there is no restriction to that process (infinite i). Extending previous simulation results for the completely reversible case, we observe that a peaked island size distribution in the intermediate time regime, in which the mean island size is increasing, crosses over to the theoretically predicted exponentially decreasing distribution at long times. It contrasts with the partially reversible model, in which peaked distributions are obtained until the long time frozen state, which is attained with a crossover time $\tau \sim \frac{i^3}{\epsilon}$. The mean island size at saturation varies as $S_{sat}\approx 2i+C\epsilon$ (C constant), while the completely reversible case shows an Ahrrenius dependence of the mean island size, $S\sim \epsilon^{-1/2}$. Thus, for different coverages, the effect of the critical size i on the geometric features is much stronger than that of epsilon, which may be used to infer the relevance of size-dependent detachment rates in real systems and other models.Comment: 14 pages,8 figures, accepted for publication in Physica

Head And Heck Mucoepidermoid Carcinoma: Clinicopathologic Study Of 173 Cases

Introduction: Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor, however few studies have been reported in Brazilian populations. Aim: To report clinical and pathologic data from 173 head and neck MEC treated in the Treatment and Research Center at Hospital do Câncer A. C. Camargo in São Paulo. Study design: Clinical randomized. Material and Method: From 1953 to 1997, 173 cases of MEC were found in the medical files of the center. Data were obtained from the patients' records and histological review of all cases. Results: The mean age of the patients was 44 years and 93 (53.8%) were men; parotid glands were affected in 61 cases (35.2%) and intraoral minor salivary glands in 75 (43.4%). TNM revealed 50.3% of the cases in stages I and II, and histological grading revealed 45.2%, 18.5% and 36.3% low-grade, intermediate-grade and high-grade tumors, respectively. Surgical treatment was employed in 80.3% of the cases, with neck dissection in 52 cases (30.1%), and radiotherapy in 73 (42.2%). Local recurrence, regional and distant metastases were found in 12.7%, 9.8% and 9.2% of the patients, respectively; 5-year and 10-year overall survival rates were 70% and 60%, respectively. Conclusions: MEC affected mainly the parotid gland and the palate of adults, without gender preference. Half of the cases were diagnosed at initial clinical stages and 64% of the tumors were low or intermediate-grade lesions. Surgery was the treatment of choice and prognosis was good.685679684Ellis, G.L., Auclair, P.L., Gnepp, D.R., Surgical Pathology of the salivary glands (1991) Major Problems in Pathology Series, 25. , Philadelphia: WB Saunders CompanyEllis, G.L., Auclair, P.L., Tumors of the Salivary Glands (1996) Armed Forces Institute of Pathology. Atlas of Tumor Pathology. 3 rd Series, , Fascicle 17. 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