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Maarten Van Dyck 《Studies in history and philosophy of science》2009,40(3):315-318
In this paper I challenge Paolo Palmieri’s reading of the Mach—Vailati debate on Archimedes’ proof of the law of the lever. I argue that the actual import of the debate concerns the possible epistemic (as opposed to merely pragmatic) role of mathematical arguments in empirical physics, and that construed in this light Vailati carries the upper hand. This claim is defended by showing that Archimedes’ proof of the law of the lever is not a way of appealing to a non-empirical source of information, but a way of explicating the mathematical structure that can represent the empirical information at our disposal in the most general way. 相似文献
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W. Emser R. Dechoux M. Weiland A. Wirz-Justice 《Cellular and molecular life sciences : CMLS》1993,49(8):686-687
In a double-blind placebo crossover study of 13 healthy volunteers, the pineal hormone melatonin (10 mg) was given at 4 pm, and the electroretinogram measured under conditions of dark and light adaptation. A significant diminution of b-wave amplitude was found under both photopic (=5.4 V, p<0.05) and scotopic conditions (=7.4 V, p<0.01). These data indicate that melatonin may transduce the dark signal at the level of the retina as well as the pineal. Acute administration of melatonin decreases sensitivity to light. 相似文献
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The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed. 相似文献
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Summary Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in several brain regions of normal and streptozotocin-induced diabetic rats. The diabetic rats exhibited significant increase in ChAT activity (p<0.05) in all brain regions studied except for the cortex and the midbrain. Meanwhile, the diabetes condition was associated with significant increase (p<0.05) in AChE activity of the bulbus olfactorius, medulla oblongata and cerebellum. These data suggest that uncontrolled diabetes is associated with significant alterations in the brain cholinergic systems.To whom requests of reprints should be addressed.This work was supported by grants from the National Aeronautics and Space Administration (NSG 2183 and NAG-2-411), a grant from the National Institutes of Health (NIH Grant RR0811) and a grant from the Division of Research Resources, National Institutes of Health (NIH Grant RR03020). 相似文献
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M. M. Brauer S. Kanovich G. Casanova J. R. Sotelo 《Cellular and molecular life sciences : CMLS》1985,41(12):1605-1607
Summary The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed. 相似文献
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Longitudinal continuity of the subrhabdomeric cisternae in the photoreceptors of the compound eye of the drone, Apis mellifera 总被引:1,自引:0,他引:1
It is shown that the subrhabdomeric cisternae of the honey bee drone photoreceptor cell constitute a single structure with a continuous lumen, that extends over at least 15 micron and perhaps the whole length of the cell. In this case, the structure of the cisternae might subserve the propagation of light adaptation along the cell. 相似文献
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Summary 4 of the 5 species ofLimnodynastes of theperoni group show 2n=24. Onlysalmini has 2n=22, thus resembling the species ofPlatyplectron (thedorsalis andornatus complexes) which all show 22 chromosomes. This 2nd group also includes species (ornatus) with very low DNA amounts. From a karyological point of view, the species of thePlatyplectron (plus eventuallysalmini) group appear more differentiated than the species of theperoni group, from which they have probably arisen.Research partly supported by a contribution from C.N.R., Rome. 相似文献
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Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in several brain regions of normal and streptozotocin-induced diabetic rats. The diabetic rats exhibited significant increase in ChAT activity (p less than 0.05) in all brain regions studied except for the cortex and the midbrain. Meanwhile, the diabetes condition was associated with significant increase (p less than 0.05) in AChE activity of the bulbus olfactorius, medulla oblongata and cerebellum. These data suggest that uncontrolled diabetes is associated with significant alterations in the brain cholinergic systems. 相似文献
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C. M. B. Ricotta 《Cellular and molecular life sciences : CMLS》1957,13(12):491-492
Riassunto I particolati delle uova vergini di riccio di mare possono essere separati, a mezzo della centrifugazione differenziale, in due frazioni, una fortemente ed una scarsamente pigmentata. La prima mostra una attività ATPasica attivata da Mg con un massimo a pH 8.2; il massimo della seconda è invece a pH 6.4. Nelle preparazioni contenenti i due tipi di particolati si ritrovano i due massimi. 相似文献
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J C Allain S Bazin M Le Lous A Delaunay 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,284(12):1131-1134
The tension developed in Rat skin by hydrothermal shrinkage is modified with ageing of the animals: the temperature of maximum tension decreases from birth to 1 month, then very slowly increases with age. At higher temperatures than that of maximum tension a relaxation occurs very rapidly in young Rats and in not yet senescent adult skins. These modifications appeared to be related to those of the nature of the intermolecular collagen cross-links with ageing. 相似文献
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E. -G. Peeters 《Cellular and molecular life sciences : CMLS》1987,43(1):74-81
Summary The author reviews the background of the soil-cancer relationship. The study then goes into geocarcinogenic diseases in relation to soil composition, looking first at general factors: soil concentrations of selenium, caesiumrubidium-potassium, trace elements; natural radioactivity risks; cancer risks in connection with recycled waste water. In its final part, the study examines geocarcinogenic diseases linked with soil composition covering gastric cancer, cancer of the esophagus, urinary, breast, and bronchial cancer, pleural mesotheliomae and bone cancer. 相似文献
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F. A. Zydeck 《Cellular and molecular life sciences : CMLS》1970,26(1):88-90
Résumé La production d'un anticorps contre le virus de l'encéphalite canine a été démontrée par électroprécipitation sur l'acétate de cellulose dans une dilution de 18. Une bande de précipitation bien définie a été obtenue dans un intervalle de temps très court, ce qui indiquerait que le test pourrait servir à l'identification de l'antigène encéphalitique chez les chiens suspectés d'en être atteints.
The author wishes to thank Dr. C. M.Sheldon of the Eli Lilly Co. for performing the serum neutralization test. This work was supported in part by PHS Research Grant No. FR00437-01A1 from the Animal Resources Branch of the Division of Research Facilities and Resources. 相似文献
The author wishes to thank Dr. C. M.Sheldon of the Eli Lilly Co. for performing the serum neutralization test. This work was supported in part by PHS Research Grant No. FR00437-01A1 from the Animal Resources Branch of the Division of Research Facilities and Resources. 相似文献
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Summary The stimulation of the crista ampullaris of the lateral canal by a short ampullopetal liquid flux produces on the pre-ganglionic vestibular fibres the appearance of a bimodal action potential. The amplitude of this action potential increases with the intensity of the stimulation. This stimulation also provokes the birth of an evoked potential at the level of the vestibular nuclei as well as an ocular jerk.Supported by the D.G.R.S.T. grant 77.7.0669 and I.N.S.E.R.M. (A.S.R. No. 6, grant 011). 相似文献
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E G Peeters 《Experientia》1987,43(1):74-81
The author reviews the background of the soil-cancer relationship. The study then goes into geocarcinogenic diseases in relation to soil composition, looking first at general factors: soil concentrations of selenium, caesium-rubidium-potassium, trace elements; natural radioactivity risks; cancer risks in connection with recycled waste water. In its final part, the study examines geocarcinogenic diseases linked with soil composition covering gastric cancer, cancer of the esophagus, urinary, breast, and bronchial cancer, pleural mesotheliomae and bone cancer. 相似文献