As Racines sociales de la science

Tradução do capítulo "The social roots of science" do livro 'The Social origins of Modern Science", de Edgar Zilsel

Variational description of multi-fluid hydrodynamics: Uncharged fluids

We present a formalism for Newtonian multi-fluid hydrodynamics derived from an unconstrained variational principle. This approach provides a natural way of obtaining the general equations of motion for a wide range of hydrodynamic systems containing an arbitrary number of interacting fluids and superfluids. In addition to spatial variations we use ``time shifts'' in the variational principle, which allows us to describe dissipative processes with entropy creation, such as chemical reactions, friction or the effects of external non-conservative forces. The resulting framework incorporates the generalization of the entrainment effect originally discussed in the case of the mixture of two superfluids by Andreev and Bashkin. In addition to the conservation of energy and momentum, we derive the generalized conservation laws of vorticity and helicity, and the special case of Ertel's theorem for the single perfect fluid. We explicitly discuss the application of this framework to thermally conducting fluids, superfluids, and superfluid neutron star matter. The equations governing thermally conducting fluids are found to be more general than the standard description, as the effect of entrainment usually seems to be overlooked in this context. In the case of superfluid He4 we recover the Landau--Khalatnikov equations of the two-fluid model via a translation to the ``orthodox'' framework of superfluidity, which is based on a rather awkward choice of variables. Our two-fluid model for superfluid neutron star matter allows for dissipation via mutual friction and also ``transfusion'' via beta-reactions between the neutron fluid and the proton-electron fluid.Comment: uses RevTeX 4; 20 pages. To appear in PRD. v2: removed discussion of charged fluids and coupling to electromagnetic fields, which are submitted as a separate paper for a clearer presentation v3: fixed typo in Eq.(9), updated some reference

Hermeneutics and Nature

This paper contributes to the on-going research into the ways in which the humanities transformed the natural sciences in the late Eighteenth and early Nineteenth Centuries. By investigating the relationship between hermeneutics -- as developed by Herder -- and natural history, it shows how the methods used for the study of literary and artistic works played a crucial role in the emergence of key natural-scientific fields, including geography and ecology

Liquid 4He: contributions to first principles theory of quantized vortices, thermohydrodynamic properties, and the lambda transition

Liquid 4He has been studied extensively for almost a century, but there are still a number of outstanding weak or missing links in our comprehension of it. This paper reviews some of the principal paths taken in previous research and then proceeds to fill gaps and create an integrated picture with more complete understanding through first principles treatment of a realistic model that starts with a microscopic, atomistic description of the liquid. Newly derived results for vortex cores and thermohydrodynamic properties for a two-fluid model are used to show that interacting quantized vortices may produce a lambda anomaly in specific heat near the superfluid transition where flow properties change. The nature of the order in the superfluid state is explained. Experimental support for new calculations is exhibited, and a unique specific heat experiment is proposed to test predictions of the theory. Relevance of the theory to modern research in cosmology, astrophysics, and Bose-Einstein condensates is discussed.Comment: 155 pages, 28 figure

‘A place of great trust to be supplied by men of skill and integrity’: assayers and knowledge cultures in late sixteenth-and seventeenth-century London

This article suggests that institutional workshops of assay were significant experimental sites in early modern London. Master assayers at Goldsmiths’ Hall on Foster Lane, in the heart of the city, and at the Royal Mint, in the Tower, made trials to determine the precious-metal content of bullion, plate and coinage. The results of their metallurgical experiments directly impacted upon the reputations and livelihoods of London's goldsmiths and merchants, and the fineness of coin and bullion. Engaged in the separation and transformation of matter, assayers and the affairs of their workshops were also a curiosity for those interested in the secrets of nature. Making use of a wide-ranging body of sources, including institutional court minutes, artisanal petitions, mercantile guidebooks, recipe books and natural-philosophical treatises, this article uncovers a complex culture of metropolitan expertise. We first examine the workshop spaces in which assayers undertook their professional activities, and their secretive corporate cultures. We turn next to the manuscript culture through which assayers codified and communicated knowledge, ‘secrets’ and techniques to broader urban audiences. Finally, we assess exchanges and tensions between assayers and the wider community of Londoners engaged in scientific knowledge production and dissemination

Artesãos, cartografia e império. A produção social de um instrumento náutico no mundo ibérico, 1500-1650

Explicar cómo y en qué condiciones fueron construidos algunos de los instrumentos científicos más emblemáticos del mundo moderno sigue siendo un desafío para los historiadores de la ciencia y de la tecnología. Este principio afecta también a los instrumentos náuticos. Así, el objetivo del presente artículo es considerar el “cómo” y el “en qué condiciones”, en un sentido amplio, analizando uno de estos artefactos: las cartas náuticas construidas durante la expansión marítima europea. Originalidad: La originalidad del texto no reside únicamente en llevar a cabo una reconstrucción de este instrumento en Portugal y España que aporte nuevos datos sobre su proceso de fabricación y sus fabricantes, sino también en arrojar luz sobre antiguos debates historiográficos que subyacen a la génesis de la ciencia moderna, tales como la difícil colaboración entre hombres prácticos y hombres teóricos; la aportación de comunidades de artesanos al mundo del conocimiento; el papel que los saberes prácticos tuvieron en el establecimiento de nuevas formas de estandarización en ciencia; la adopción de una metodología empírica para el dominio del mundo o la construcción de grandes imperios globales cimentados sobre la base del trabajo manual. Metodología: El análisis de estos debates requiere una aproximación metodológica que atienda a las categorías y los conceptos principales puestos en circulación tanto por la historia como por la filosofía de la ciencia más reciente. En definitiva, se trata de atender a las condiciones que permitieron el establecimiento de acuerdos (y también de controversias) epistemológicos entre diferentes comunidades de conocimiento tomando un instrumento náutico como “mediador”. Conclusiones: El artículo concluye que la consideración de las culturas empíricas del conocimiento y sus realizaciones materiales son una condición sine qua non para entender la génesis de la modernidad científica europea y la construcción de un mundo globalExplaining how and under what conditions some of the most emblematic scientific instruments of the modern world were built remains a challenge for historians of science and technology. This principle also affects nautical instruments. Thus, the objective of this article is to consider the “how” and the “under what conditions”, in a broad sense, by examining one of these devices: the nautical charts developed during the European maritime expansion. Originality: The originality of this article lies not only in the reconstruction of this instrument in Portugal and Spain, providing new information about its development process and its manufacturers, but also in shedding light on old historiographical debates that underlie the genesis of modern science, such as the difficult collaboration between practical men and theoretical men; the contribution of artisan communities to the world of knowledge; the role that practical knowledge played in the establishment of new forms of standardization in science; the adoption of an empirical methodology for achieving mastery of the world or the construction of large global empires founded upon manual labor. Methodology: Analyzing these debates requires a methodological approach that addresses the main categories and concepts put into circulation by the most recent history and philosophy of science. In short, unveiling the conditions that enabled the establishment of epistemological agreements (and also disputes) between different knowledge communities by taking a nautical instrument as “mediator.” Conclusions: The article concludes that examining empirical knowledge cultures and their material achievements are a sine qua non condition to understand the genesis of European scientific modernity and the construction of a global worldExplicar como e em que condições foram construídos alguns dos instrumentos científicos mais emblemáticos do mundo moderno continua sendo um desafio para os historiadores da ciência e da tecnologia. Esse princípio afeta também os instrumentos náuticos. Assim, o objetivo do presente artigo é considerar o “como” e o “em que condições”, em um sentido amplo, e analisar um desses artefatos: as cartas náuticas construídas durante a expansão marítima europeia. Originalidade: A originalidade do texto não reside unicamente na realização de uma reconstrução desse instrumento em Portugal e na Espanha de forma que traga novos dados sobre seu processo de fabricação e de seus fabricantes, mas também em lançar luz sobre antigos debates historiográficos que subjazem à gênese da ciência moderna, tais como a difícil colaboração entre homens práticos e homens teóricos, a contribuição de comunidades de artesãos ao mundo do conhecimento; o papel que os saberes práticos tiveram no estabelecimento de novas formas de padronização na ciência, a adoção de uma metodologia empírica para o domínio do mundo ou a construção de grandes impérios globais cimentados sobre a base do trabalho manual. Metodologia: A análise desses debates requer uma aproximação metodológica que atenda às categorias e aos principais conceitos colocados em circulação tanto pela história quanto pela filosofia da ciência mais recente. Definitivamente, trata-se de atender às condições que permitiram o estabelecimento de acordos (e também de controvérsias) epistemológicos entre diferentes comunidades de conhecimento tomando o instrumento náutico como “mediador”. Conclusões: O artigo conclui que a consideração das culturas empíricas do conhecimento e suas realizações materiais são uma condição sine qua non para entender a gênese da modernidade científica europeia e a construção de um mundo globa

Studies on inter-species expression of photosynthesis genes in Rhodobacter capsulatus

The primary amino acid sequences of the L, M, and H photosynthetic reaction center peptide subunits from a number of purple non-sulfur bacteria, including Rhodopseudomonas viridis, Rhodobacter sphaeroides, and Rhodobacter capsulatus have been previously shown to be highly homologous, and detailed X-ray crystallographic analyses of reaction centers from two species of purple non-sulfur bacteria, Rps. viridis and R. sphaeroides have shown that all recognized structural and functional features are conserved. Experiments were undertaken to determine whether genes encoding reaction center and light harvesting peptide subunits from one species could be functionally expressed in other species. Plasmid-borne copies of R sphaeroides and Rps. viridis pigment binding-peptide genes were independently introduced into a photosynthetically incompetent R. capsulatus mutant host strain, deficient in all known pigment-binding peptide genes. The R. sphaeroides puf operon, which encodes the L and M subunits of the reaction center as well as both peptide subunits of light harvesting complex I, was shown to be capable of complementing the mutant R. capsulatus host. Hybrid reaction centers, comprised of R. sphaeroides-encoded L and M subunits and an R. capsulatus-encoded H subunit, were formed in addition to the R. sphaeroides-encoded LHI complexes. These hybrid cells were capable of photosynthetic growth, but their slower growth rates under low light conditions and their higher fluorescence emission levels relative to cells containing native complexes, indicated an impairment in energy transduction. The Rps. viridis puf operon was found to be incapable of functional expression in the R. capsulatus mutant host. Introduction of a plasmid-borne copy of the Rps. viridis puhA gene, which encodes the H subunit of the reaction center, into host cells already containing the Rps. viridis puf operon, such that all structural peptides of the Rps. viridis reaction center were present, still did not permit stable assembly of Rps. viridis photosynthetic complexes. RNA blot analysis demonstrated that the barrier to functional expression was not at the level of transcription. Differences between Rps. viridis and R. sphaeroides that may account for their differing abilities to complement the R. capsulatus mutant host strain are discussed.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat