Leibniz's Observations on Hydrology: An Unpublished Letter on the Great Lombardy Flood of 1705

Although the historical reputation of Gottfried Wilhelm Leibniz (1646–1716) largely rests on his philosophical and mathematical work, it is widely known that he made important contributions to many of the emerging but still inchoate branches of natural science of his day. Among the many scientific papers Leibniz published during his lifetime are ones on the nascent science we now know as hydrology. While Leibniz's other scientific work has become of increasing interest to scholars in recent years, his thinking about hydrology has been neglected, despite being relatively broad in extent, including as it does papers on the ‘raising of vapours’ and the formation of ice, as well as the separation of salt and fresh water. That list can now be extended still further following the discovery of a previously unpublished letter of Leibniz's on the causes of the devastating Lombardy flood of October and November 1705. This letter, which will be the focus of our paper, reveals the depth of Leibniz's understanding of key hydrological processes. In it, he considers various mechanisms for the flood, such as heavy rains on high ground, underwater earthquakes, and a mountain collapse. Over the course of the paper we examine each of these mechanisms in depth, and show that Leibniz was in the vanguard of hydrological thinking. We also show that the letter contains one of the first scholarly attempts to apply aspects of the still-forming notion of the hydrological cycle to account for a flood event.     

Delta opioid receptors recycle to the membrane after sorting to the degradation path

Soon after internalization delta opioid receptors (DOPrs) are committed to the degradation path by G protein-coupled receptor (GPCR)-associated binding protein. Here we provide evidence that this classical post-endocytic itinerary may be rectified by downstream sorting decisions which allow DOPrs to regain to the membrane after having reached late endosomes (LE). The LE sorting mechanism involved ESCRT accessory protein Alix and the TIP47/Rab9 retrieval complex which supported translocation of the receptor to the TGN, from where it subsequently regained the cell membrane. Preventing DOPrs from completing this itinerary precipitated acute analgesic tolerance to the agonist DPDPE, supporting the relevance of this recycling path in maintaining the analgesic response by this receptor. Taken together, these findings reveal a post-endocytic itinerary where GPCRs that have been sorted for degradation can still recycle to the membrane.     

浅议我国入世后对国内建筑业的影响及其对策

本文简要论述了我国建筑市场将面临的新的发展机遇,分析了我国加入世界贸易组织后对建筑业的有利与不利因素,讨论了我国建筑业进入国际市场的前景,建议了应对策略和政府的政策导向。     

Reference to the best explanation

This paper shows that two questions productively overlap: first, in virtue of what does an agent infer one hypothesis rather than another? Second, in virtue of what does an agent refer to one natural kind rather than another? Peter Lipton (2004) answers the first question by articulating the model of inference to the best explanation. Lipton’s answer to the first question is appropriated as an answer to the second.     

From proportion to balance: the background to symmetry in science

We call attention to the historical fact that the meaning of symmetry in antiquity—as it appears in Vitruvius’s De architectura—is entirely different from the modern concept. This leads us to the question, what is the evidence for the changes in the meaning of the term symmetry, and what were the different meanings attached to it? We show that the meaning of the term in an aesthetic sense gradually shifted in the context of architecture before the image of the balance was attached to the term in the middle of the 18th century and well before the first modern scientific usage by Legendre in 1794.     

Impulse propagation from the SA-node to the ventricles

Normally the pacemaker of the mammalian heart is located in the sinus node. In the rabbit the sinus node can be subdivided into two regions, the center of the node where the impulse originates and the border zone through which the impulse is conducted towards the atrium. Conduction properties of both regions were investigated. It appeared that conduction velocity increases and refractoriness decreases when one goes from the nodal center towards the atrium. The tissue mass of the atrium is large in comparison to the sinus node and normally the resting membrane potential of atrial fibers is more negative than that of nodal fibers; consequently, a potential difference exists causing a current flow between both areas. Evidently this hyperpolarizing current flow depresses impulse formation in the border zone fibers which have better intrinsic pacemaker properties than fibers in the nodal center. If the impulse has reached the atrium it is conducted with a relatively high safety factor and will reach the AV node in principle without difficulty. The AV node, if deprived of sinus nodal dominance, develops spontaneous activity originating from the lower nodal fibers. Also in this structure, electrotonic depression by surrounding tissue causes deceleration of the pacemaker.     

Impulse propagation from the SA-node to the ventricles

Summary Normally the pacemaker of the mammalian heart is located in the sinus node. In the rabbit the sinus node can be subdivided into two regions, the center of the node where the impulse originates and the border zone through which the impulse is conducted towards the atrium. Conduction properties of both regions were investigated. It appeared that conduction velocity increases and refractoriness decreases when one goes from the nodal center towards the atrium. The tissue mass of the atrium is large in comparison to the sinus node and normally the resting membrane potential of atrial fibers is more negative than that of nodal fibers; consequently, a potential difference exists causing a current flow between both areas. Evidently this hyperpolarizing current flow depresses impulse formation in the border zone fibers which have better intrinsic pacemaker properties than fibers in the nodal center. If the impulse has reached the atrium it is conducted with a relatively high safety factor and will reach the AV node in principle without difficulty. The AV node, if deprived of sinus nodal dominance, develops spontaneous activity originating from the lower nodal fibers. Also in this structure, electrotonic depression by surrounding tissue causes deceleration of the pacemaker.     

Adaptation of the guinea-pig to histamine. sensitivity of the guinea-pig's ileum to histamine and acetylcholine

Résumé L'adaptation des cobayes à l'histamine par voie intrapéritonéale diminue la sensibilité de leur jéjunum isolé à l'histamine. En même temps le jéjunum isolé de cobayes adaptés réagit à l'acétylcholine sans changer remarquablement de susceptibilité. L'activité de l'histaminase dans le jéjunum adapté ne démontre pas la différence en relation avec celle du jéjunum non adapté.

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The study was supported by the Polish Academy of Sciences.     

A system in the mammalian skin sensitive to X irradiation and insensitive to the oxygen effect

Résumé La chute de pression sous l'influence des rayons X dans une poche de solution saline injectée dans la peau du rat (phénomène décrit parBrinkman etLamberts) se produit aussi en l'absence d'oxygène. L'action de certains radioprotecteurs, mise en évidence par cette technique, est donc également indépendante de l'oxygène.

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Fellow of the Belgo-Italian Commission for Cultural Relations.