Newton,Gases, and Daltonian chemistry: The foundations of combination in definite proportion

This study deals with the relationship between Newton's gas model in the Principia (Book II, Proposition xxiii) and Dalton's theorizing. Dalton's first theory of mixed gases is an elegant extension of the Newtonian gas model which, in turn, led Dalton to a general model of chemical combination. The views on combination are contrasted with those of Arnold Thackray. Interestingly, the model of combination was knowingly based on a falsified theory.     

Disciplines,models, and computers: The path to computational quantum chemistry

Many disciplines and scientific fields have undergone a computational turn in the past several decades. This paper analyzes this sort of turn by investigating the case of computational quantum chemistry. The main claim is that the transformation from quantum to computational quantum chemistry involved changes in three dimensions. First, on the side of instrumentation, small computers and a networked infrastructure took over the lead from centralized mainframe architecture. Second, a new conception of computational modeling became feasible and assumed a crucial role. And third, the field of computational quantum chemistry became organized in a market-like fashion and this market is much bigger than the number of quantum theory experts. These claims will be substantiated by an investigation of the so-called density functional theory (DFT), the arguably pivotal theory in the turn to computational quantum chemistry around 1990.     

Ketoconazole,an inhibitor of calcium transport in skeletal muscle sarcoplasmic reticulum

Summary Ketoconazole, an antimycotic agent, inhibits calcium binding and accumulation, and induces calcium release in sarcoplasmic reticulum. The Mg²⁺-ATPase and the (Ca²⁺+Mg²⁺)-ATPase activities are stimulated at low but inhibited at high concentrations of ketoconazole.The author wishes to thank Dr K. S. Cheah for discussion and Mr C. C. Ketteridge for preparing the sarcoplasmic reticulum and carrying out the ATPase assays.     

Bardet-Biedl syndrome: an emerging pathomechanism of intracellular transport

From a handful of uncloned genetic loci 6 years ago, great strides have been made in understanding the genetic and molecular aetiology of Bardet-Biedl syndrome (BBS), a rare pleiotropic disorder characterised by a multitude of symptoms, including obesity, retinal degeneration and cystic kidneys. Presently, 11 BBS genes have been cloned, with the likelihood that yet more BBS genes remain undiscovered. In 2003, a major breakthrough was made when it was shown that BBS is likely caused by defects in basal bodies and/or primary cilia. Since then, studies in numerous animal models of BBS have corroborated the initial findings and, in addition, have further refined the specific functions of BBS proteins. These include roles in establishing planar cell polarity (noncanonical Wnt signaling) in mice and zebrafish, modulating intraflagellar transport and lipid homeostasis in worms, and regulating intracellular trafficking and centrosomal functions in zebrafish and human tissue culture cells. From these discoveries, a common theme has emerged, namely that the primary function of BBS proteins may be to mediate and regulate microtubule-based intracellular transport processes. Received 20 April 2006; received after revision 30 May 2006; accepted 15 June 2006     

The notion of nature in chemistry

If nature is by definition the object of the natural sciences, then the dichotomy ‘natural’ versus ‘chemical’, held by both chemists and nonchemists, suggests an idiosyncrasy of chemistry. The first part of the paper presents a selective historical analysis of the main notions of nature in chemistry, as developed in early Christian views of chemical crafts, alchemy, iatrochemistry, mechanical philosophy, organic chemistry, and contemporary drug research. I argue that the dichotomy as well as quasi-moral judgments of chemistry have been based on static and teleological notions of nature throughout history and that chemists, unlike physicists, have neglected the dynamic notion of nature. The second part provides a philosophical criticism of the former notions and argues for the latter as well as for an explicit discourse about values in chemistry.     

The carbon cycle: Sources and sinks of atmospheric CO2

Summary In this contribution we try to give a synopsis of the more important processes within the global C cycle. Special attention is paid to the mechanisms by which atmospheric CO₂ is interchanged between the biosphere and the oceans, and existing qualitative and quantitative uncertainties are pointed out.     

The specification of asymmetric configuration in organic chemistry

Zusammenfassung Ein früherer Vorschlag⁴ für die Spezifizierung der asymmetrischen Konfiguration organischer Verbindungen wurde modifiziert und erweitert. In der vorliegenden Abhandlung wird mehr Nachdruck auf Beispiele gelegt, welche das Verfahren erläutern, als auf eine formelle Darlegung der Prinzipien in allgemeiner Form. Die prinzipiellen und praktischen Gründe, welche für ein allgemeines Verfahren zur Spezifizierung der absoluten asymmetrischen Konfigurationen sprechen, werden diskutiert. Da ein solches Verfahren nur auf wenigen eindeutigen Regeln beruhen soll, muss es folgende Bedingungen erfüllen: 1. die Reste, welche die Asymmetric bedingen, müssen auf Grund einer permanenten, internen Eigenschaft geordnet werden; 2. das dreidimensionale Muster, welches so erhalten wird, muss direkt als Klassifikationsgrundlage dienen.Ebenso wie in der früheren Mitteilung wird auch in der vorliegenden Abhandlung als ordnende Eigenschaft von Gruppen, welche sich in ihrer chemischen Konstitution unterscheiden, die Atomnummer verwendet. Darüber hinaus wird gezeigt, wie die feineren Unterschiede, welche Asymmetrie verursachen, wie die Atommasse sowie Konfiguration und Position der Gruppen, berücksichtigt werden können.Das Verfahren wurde soweit ausgebaut, dass man es auf alle bekannten Typen der optischen Isomerie organischer Verbindungen anwenden kann. Zur Spezifizierung der Konfiguration werden neue Symbole vorgeschlagen, welche ausschliesslich die absolute Konfiguration darstellen sollen.     

The astrorhizae of fossil stromatoporoids closely approximate an energetically optimal fluid transport system

Direct measurements on 375 million year old stromatoporoid sponges show that the astrorhizal canals (excurrent flow channels) have a near-optimal architecture; they are configured such that the energetic costs to construct and operate these fluid transport systems averaged only 2.54% above those of equivalent Murray's Law systems, the theoretical minimum. The average cost incurred by the fluid transport system in stromatoporoids was a factor of three closer to the Murray's Law optimum than are vessel networks in the circulatory system of mammals.     

Kant and the nature of matter: Mechanics,chemistry, and the life sciences

Kant believed that the ultimate processes that regulate the behavior of material bodies can be characterized exclusively in terms of mechanics. In 1790, turning his attention to the life sciences, he raised a potential problem for his mechanically-based account, namely that many of the operations described in the life sciences seemed to operate teleologically. He argued that the life sciences do indeed require us to think in teleological terms, but that this is a fact about us, not about the processes themselves. Nevertheless, even were we to concede his account of the life sciences, this would not secure the credentials of mechanics as a general theory of matter. Hardly any material properties studied in the second half of the eighteenth century were, or could have been, conceived in mechanical terms. Kant's concern with teleology is tangential to the problems facing a general matter theory grounded in mechanics, for the most pressing issues have nothing to do with teleology. They derive rather from a lack of any connection between mechanical forces and material properties. This is evident in chemistry, which Kant dismisses as being unscientific on the grounds that it cannot be formulated in mechanical terms.     

Mitochondria dynamism: of shape,transport and cell migration

Mitochondria are highly dynamic and functionally versatile organelles that continuously fragment and fuse in response to different physiological needs of the cell. The list of proteins that strictly regulate the morphology of these organelles is constantly growing, adding new players every day and new pieces to the comprehension and elucidation of this complex machinery. The structural complexity of mitochondria is only paralled by their functional versatility. Indeed, changes in mitochondria shape play critical roles in vertebrate development programmed cell death and in various processes of normal cell physiology, such as calcium signaling, reactive oxygen species production, and lifespan. Here, we present the latest findings on the regulation of mitochondrial dynamics and some of their physiological roles, focusing on cell migration. In cells where migration represents a crucial function in their physiology, such as T and tumoral metastatic cells, mitochondria need to be fragmented and recruited to specific subcellular regions to make movement possible. In depth analysis of this role of mitochondrial dynamics should help in identifying potential targeted therapy against cancer or in improving the immune system’s efficiency.     

The discovery of atmospheric condensation nuclei by Paul-Jean Coulier in 1875

Zusammenfassung 1875 hatPaul-Jean Coulier, Professor für Chemie und Hygiene an der Medizinischen Militärschule Val de Grâce in Paris, mit einfachen Mitteln die Rolle der atmosphärischen Kondensationskerne bei der Nebelbildung entdeckt und viele wesentliche Tatsachen beschrieben. Erst 5 Jahre später erfolgte die erste Arbeit vonAitken. Die Geschichte dieser Entdeckung und die Ursache dafür, dass sie nicht besser bekannt wurde, wird besprochen.     

Dynamic mechanistic explanation: computational modeling of circadian rhythms as an exemplar for cognitive science

We consider computational modeling in two fields: chronobiology and cognitive science. In circadian rhythm models, variables generally correspond to properties of parts and operations of the responsible mechanism. A computational model of this complex mechanism is grounded in empirical discoveries and contributes a more refined understanding of the dynamics of its behavior. In cognitive science, on the other hand, computational modelers typically advance de novo proposals for mechanisms to account for behavior. They offer indirect evidence that a proposed mechanism is adequate to produce particular behavioral data, but typically there is no direct empirical evidence for the hypothesized parts and operations. Models in these two fields differ in the extent of their empirical grounding, but they share the goal of achieving dynamic mechanistic explanation. That is, they augment a proposed mechanistic explanation with a computational model that enables exploration of the mechanism’s dynamics. Using exemplars from circadian rhythm research, we extract six specific contributions provided by computational models. We then examine cognitive science models to determine how well they make the same types of contributions. We suggest that the modeling approach used in circadian research may prove useful in cognitive science as researchers develop procedures for experimentally decomposing cognitive mechanisms into parts and operations and begin to understand their nonlinear interactions.     

The autonomy of models and explanation: anomalous molecular rearrangements in early twentieth-century physical organic chemistry

During the 1930s and 1940s, American physical organic chemists employed electronic theories of reaction mechanisms to construct models offering explanations of organic reactions. But two molecular rearrangements presented enormous challenges to model construction. The Claisen and Cope rearrangements were predominantly inaccessible to experimental investigation and they confounded explanation in theoretical terms. Drawing on the idea that models can be autonomous agents in the production of scientific knowledge, I argue that one group of models in particular were functionally autonomous from the Hughes–Ingold theory. Cope and Hardy’s models of the Claisen and Cope rearrangements were resources for the exploration of the Hughes–Ingold theory that otherwise lacked explanatory power. By generating ‘how-possibly’ explanations, these models explained how these rearrangements could happen rather than why they did happen. Furthermore, although these models were apparently closely connected to theory in terms of their construction, I argue that partial autonomy issued in extra-logical factors concerning the attitudes of American chemists to the Hughes–Ingold theory. And in the absence of a complete theoretical hegemony, a degree of consensus was reached concerning modelling the Claisen rearrangement mechanism.     

The end of an error: Bianchini,Regiomontanus, and the tabulation of stellar coordinates

Archive for History of Exact Sciences - Giovanni Bianchini’s fifteenth-century Tabulae primi mobilis is a collection of 50 pages of canons and 100 pages of tables of spherical astronomy and...     

A farnesyl arabinoside as an enhancer of glucose transport in rat adipocytes from a soft coral,Sinularia sp.

Separation of a lipophilic extract of a soft coral,Sinularia sp., assayed by enhancement of glucose transport in rat adipocytes, gave farnesyl 4-O--D-arabinopyranosyl--D-arabinopyranoside-2,2,3-triacetate (1a) whose structure was determined by spectroscopy. Enhancers of glucose transport may be useful for the prevention and treatment of diabetic disorders.     

A farnesyl arabinoside as an enhancer of glucose transport in rat adipocytes from a soft coral, Sinularia sp.

Separation of a lipophilic extract of a soft coral, Sinularia sp., assayed by enhancement of glucose transport in rat adipocytes, gave farnesyl 4-O-beta-D-arabinopyranosyl-beta-D-arabinopyranoside-2,2',3- triacetate (1a) whose structure was determined by spectroscopy. Enhancers of glucose transport may be useful for the prevention and treatment of diabetic disorders.     

The double transfer of thermodynamics: From physics to chemistry and from Europe to America

The aim of this study is twofold: to explore, first, the influence of the intellectual and social conditions on the transfer of thermodynamics to chemistry and thereby the making of chemical thermodynamics, and second, the way that this knowledge was transferred from Europe to America. Consequently, it is of interest to examine the methodological approaches used by physicists and chemists to transfer thermodynamics to chemistry, to evaluate the potential of this science to offer solutions to existing chemical problems, and to discuss the attitude of the scientific community towards these new ideas. The development of chemical thermodynamics in America followed a different route compared to the European experience. Although it was transferred from Europe, it had distinctive characteristics imposed by a different traditional, intellectual and social milieu. This study focuses on the content of the transferred knowledge to America and the direction that this knowledge assumed by the American scientists. As a paradigm, the chemical thermodynamics of Gilbert Newton Lewis will be considered.