数学索隐

数学是从哪里来的？它是早已存在着等待我们去发现的,还是人类在进步中把它制造出来的？柏拉图认为,数学概念确实在某种离奇而完美的现实中存在,这种完美的现实紧挨着宇宙的边缘。一个圆不只是一种观念,它是一种理想。我们这些不无缺陷的生物可以追求那种理想,但永远得不到它,倒不只是因为铅笔尖太粗。但是有这么一些人．他们说．数学只存在手旁观者的头脑平．它在与人类思维无关的地方并不存在,如同语言、音乐足球规则一样。它是人类想象的虚构物。自然的型式那么上面两种意见谁对？不错,在柏拉图主义者的观点中,有那种非常的诱惑…     

Radical Constructivism in Biology and Cognitive Science

This article addresses the issue of “objectivism vs constructivism” in two areas,biology and cognitive science, which areintermediate between the natural sciences suchas physics (where objectivism is dominant) andthe human and social sciences (whereconstructivism is widespread). The issues inbiology and in cognitive science are intimatelyrelated; in each of these twin areas, the “objectivism vs constructivism” issue isinterestingly and rather evenly balanced; as aresult, this issue engenders two contrastingparadigms, each of which has substantialspecific scientific content. The neo-Darwinianparadigm in biology is closely resonant withthe classical cognitivist paradigm in cognitivescience, and both of them are intrinsicallyobjectivist. The organismic paradigm inbiology, based on the concept of autopoiesis,is consonant with the paradigm of “enaction” incognitive science; the latter paradigms are bothprofoundly constructivist.In cognitive science, the objectivism vsconstructivism issue is internal to thescientific field itself and reflexivity isinescapable. At this level, strong ontologicalobjectivism is self-contradictory and thereforeuntenable. Radical constructivism isself-coherent; but it also rehabilitatesa weak form of objectivism as a pragmaticallyviable alternative. In conclusion, there is aneven-handed reciprocity between “objectivist”and “constructivist” perspectives. Finally, thearticle examines the consequences of thisconclusion for fields other than cognitivescience: biology; physics and the naturalsciences; and the human and social sciences.     

Rate of respiration in relation to autogamy inParamecium aurelia

Zusammenfassung Die Atmung einzelner Pantoffeltierchen (Paramecium aurelia) aus Serien-isolierten Kulturen wurde mit Hilfe eines Cartesischen Tauchers gemessen. Die Messungen an Individuen vor und nach Autogamie (Selbstbefruchtung) zeigten, dass die Atmung nach Autogamie in signifikanter Weise ansteigt.Da die Autogamie für das überleben der Kulturen eine grosse Wichtigkeit besitzt, ergeben sich Parallelen zwischen den Stoffwechselveränderungen beiParamecium und der Alterung der somatischen Zellen von Metazoen.     

Structural basis for nuclear import complex dissociation by RanGTP

Nuclear protein import is mediated mainly by the transport factor importin-beta that binds cytoplasmic cargo, most often via the importin-alpha adaptor, and then transports it through nuclear pore complexes. This active transport is driven by disassembly of the import complex by nuclear RanGTP. The switch I and II loops of Ran change conformation with nucleotide state, and regulate its interactions with nuclear trafficking components. Importin-beta consists of 19 HEAT repeats that are based on a pair of antiparallel alpha-helices (referred to as the A- and B-helices). The HEAT repeats stack to yield two C-shaped arches, linked together to form a helicoidal molecule that has considerable conformational flexibility. Here we present the structure of full-length yeast importin-beta (Kap95p or karyopherin-beta) complexed with RanGTP, which provides a basis for understanding the crucial cargo-release step of nuclear import. We identify a key interaction site where the RanGTP switch I loop binds to the carboxy-terminal arch of Kap95p. This interaction produces a change in helicoidal pitch that locks Kap95p in a conformation that cannot bind importin-alpha or cargo. We suggest an allosteric mechanism for nuclear import complex disassembly by RanGTP.     

Chemistry and slavery in the Scottish Enlightenment

ABSTRACT

The Scottish Enlightenment has long been identified with abolitionism because of the writings of the moral and economic philosophers and the absence of slaves in Scotland itself. However, Scots were disproportionately represented in the ownership, management, and especially medical treatment of slaves in the British Caribbean. Sugar and cotton flowed into Glasgow and young, educated Scots looking for work as traders, bookkeepers, doctors made the return trip back to the Caribbean to manage the plantations. Chemically trained doctors and agriculturalists tested their theories in the plantations and developed new theories based on their experimentation on the land and slaves. In foregrounding the participation of Scottish trained chemists in the practice of slavery, I argue that the development of eighteenth-century chemistry and the broader intellectual Enlightenment were inextricably entangled with the economic Improvement Movement and the colonial economy of the British slave trade.