Some observations on the Rohon-Beard cell perikaryon

Summary During the hatching period, the Rohon-Beard cells of Salmo gairdneri showed definite structural maturity of their perikarya, which is in contrast to the amphibian species investigated, where neuronal maturation of the Rohon-Beard cells is finished only in later — posthatching — developmental stages.     

Antoni van Leeuwenhoek and measuring the invisible: The context of 16th and 17th century micrometry

This article explores the impact of 16th and 17th-century developments in micrometry on the methods Antoni van Leeuwenhoek employed to measure the microscopic creatures he discovered in various samples collected from his acquaintances and from local water sources. While other publications have presented Leeuwenhoek's measurement methods, an examination of the context of his techniques is missing. These previous measurement methods, driven by the need to improve navigation, surveying, astronomy, and ballistics, may have had an impact on Leeuwenhoek's methods. Leeuwenhoek was educated principally in the mercantile guild system in Amsterdam and Delft. He rose to positions of responsibility within Delft municipal government. These were the years that led up to his first investigations using the single-lens microscopes he became expert at creating, and that led to his first letter to the Royal Society in 1673. He also took measures to train in surveying and liquid assaying practices existing in his time, disciplines that were influenced by Pedro Nunes, Pierre Vernier, Rene Descartes, and others. While we may never know what inspired Leeuwenhoek's methods, the argument is presented that there were sufficient influences in his life to shape his approach to measuring the invisible.     

Some observations on the Rohon-Beard cell perikaryon.

During the hatching period, the Rohon-Beard cells of Salmo gairdneri showed definite structural maturity of their perikarya, which is in contrast to the amphibian species investigated, where neuronal maturation of the Rohon-Beard cells is finished only in later -- posthatching -- developmental stages.     

A lost chapter in the pre-history of algebraic analysis: Whittaker on contact transformations

In the early 1930s W. O. Kermack and W. H. McCrea published three papers in which they attempted to prove a result of E. T. Whittaker on the solution of differential equations. In modern parlance, their key idea consisted in using quantized contact transformations over an algebra of differential operators. Although their papers do not seem to have had any impact, either then or at any later time, the same ideas were independently developed in the 1960–1980s in the framework of the theory of modules over rings of microdifferential operators. In this paper we describe the results of Kermack and McCrea and discuss possible reasons why such promising papers had no impact on the mathematics of the twentieth century.     

Some observations on the control of the tongue muscles

Zusammenfassung Es wird gezeigt, dass der Nervus hypoglossus die afferenten propriozeptiven Impulse der inneren Zungenmuskulatur der Katze nicht leiten kann. Ein bisher nicht beschriebener Reflex zwischen N. lingualis und N. hypoglossus wird erwähnt und seine eventuelle Bedeutung für die Propriozeption der Zunge wird besprochen.     

Some additional observations on the chemical nature of neutramycin

Zusammenfassung Für das Antibiotikum Neutramycin wird die Summenformel C₃₄H₅₄O₁₄ abgeleitet. Die Methanolyse lieferte die Methylglykoside der Chalcose und Mycinose.     

Some observations on carotenoid synthesis by the algaChlorella vulgaris

Zusammenfassung WirdChlorella vulgaris in einem Medium, das Glukose, Pepton und Mineralsalze enthält, gezüchtet, so synthetisiert sie sowohl in Licht wie im Dunkeln -Carotin, Lutein, Violaxanthin und Neoxanthin. Das Wachstum im Dunkeln beträgt jedoch nur 1/6 von demjenigen im Licht. Die Carotinoide verschwinden aus alten Lichtkulturen, werden aber in alten Dunkelkulturen weiter synthetisiert. Diphenylamin hemmt das Wachstum dieses Organismus bei einer Konzentration von 1/280 000 vollständig.     

Some observations on the cytology of induced interchanges inSorghum

Zusammenfassung Es wurden die induzierten Chromosomenbrüche durch Röntgenbestrahlung von Sorghumsamen und die Translokationen in der Meiose der Pollenkörner untersucht.     

Some observations on the seed coat structure within the genusEpilobium

Résumé Nous avons examiné au MEB et au microscope ordinaire l'épiderme de la graine de 17 formes du genreEpilobium provenant de l'Amérique du Nord et relevé l'utilié et la valeur taxonomique et génétique des données obtenues dans le cadre du genre.

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Acknowledgements: This work was supported in part by the NRC of Canada and the Boreal Institute of Alberta.     

Interactions between mechanics and differential geometry in the 19th century

Conclusion 79. This study of the interaction between mechanics and differential geometry does not pretend to be exhaustive. In particular, there is probably more to be said about the mathematical side of the history from Darboux to Ricci and Levi Civita and beyond. Statistical mechanics may also be of interest and there is definitely more to be said about Hertz (I plan to continue in this direction) and about Poincaré's geometric and topological reasonings for example about the three body problem [Poincaré 1890] (cf. also [Poincaré 1993], [Andersson 1994] and [Barrow-Green 1994]). Moreover, it would be interesting to find out how the 19^th century ideas discussed here influenced the developments in the 20^th century. Einstein himself is a hotly debated case.Yet, despite these shortcommings, I hope that this paper has shown that the interactions between mechanics and differential geometry is not a 20^th century invention. Klein's view (see my Introduction) that Riemannian geometry grew out of mechanics, more specifically the principle of least action, cannot be maintained. On the other hand, when Riemannian geometry became known around 1870 it was immediately used in mechanics by Lipschitz. He began a continued tradition in this field, which had several elements in common with the new view of mechanics conceived by the physicists and explicitly carried out by Hertz.Before 1870 we found only scattered interactions between differential geometry and mechanics and only direct ones for systems of two or three degrees of freedom. For more degrees of freedom the geometrical ideas were in some interesting cases taken over by analogy, but these analogies did not lead to formal introduction of geometries of more than three dimensions.