Some Spanners in the Works of Grounding Mechanisms Removed

In this paper I address two concerns with Kelly Trogdon’s grounding mechanism view, i.e. the idea that metaphysical explanation can be modeled on causal-mechanical explanation. The first concern threatens to undermine the unity that grounding-mechanical explanations imposes on metaphysical explanation; and the second concern requires the grounding mechanic to put forth a formal condition on grounding-mechanical models. After having discussed both of these, I provide a solution to the first and argue that the second concern is unwarranted.

The shear resistance of a member without shear reinforcement according to Eurocode 2; the error of the calculated value and the mechanical explanation of the problem

In this paper the shear resistance of a member without shear reinforcement according to Eurocode 2 is investigated. This expression, as most expressions of design codes typically used to estimate the nominal shear resistance, has been created based on experimental investigations. It will be verified that in case of non-prestressed reinforced concrete member without stirrups, the shear resistance is carried by the shear resistance of the compressive zone; and the shear resistance given by the empirical expression of Eurocode 2 is actually the shear resistance of the compressive zone.Knowing the mechanical background of the empirical expressions of Eurocode 2, the limits of its applicability can be shown, thus its error can be predicted. Using the reports of experimental investigations, it is easy to find cases to prove the correctness of the error-prediction. In this paper simple modifications will be suggested to Eurocode 2 shear design procedures, by which a more consistent level of safety can be ensured.

Being Alive in Descartes' Physiology: Animals and Plants, the Immutatio and the Impetus

In René Descartes' works there are four major references to living bodies as objects of his natural philosophy. The first is contained in the Fifth part of the Discours de la Méthode, published in June 1637, where Descartes provides a mechanical explanation of the heartbeat and other living functions of the body. The second is in a bio-medical note collected in the Excerpta anatomica dated November 1637, where he discusses nutrition and growth. The third is the famous claim on the absence of a section on living bodies in the Principia philosophiae, published in 1644. The fourth is in La Description du corps humain, Descartes' late physiology likely dated 1647-1648. In this article, by exploring these passages and contextualizing his physiological observations of animals and plants, I reassemble Descartes' science of life: his dismissal of soul, his mechanical framework, his interpretation of bodily self-maintenance and growth, his understanding of living bodies as integrated and organic systems, and the role of a power such as the immutatio and forces such as the impetus.

The Transient Mechanics of Muscle Require Only a Single Force-Producing Cross-Bridge State and a 100 Å Working Stroke

An informative probe of myosin cross-bridge behaviour in active muscle is a mechanical transient experiment where, for example, a fully active muscle initially held at constant length is suddenly shortened to a new fixed length, providing a force transient, or has its load suddenly reduced, providing a length transient. We describe the simplest cross-bridge mechanical cycle we could find to model these transients. We show using the statistical mechanics of 50,000 cross-bridges that a simple cycle with two actin-attached cross-bridge states, one producing no force and the other producing force, will explain much of what has been observed experimentally, and we discuss the implications of this modelling for our understanding of how muscle works. We show that this same simple model will explain, reasonably well, the isotonic mechanical and X-ray transients under different loads observed by Reconditi et al. (2004, Nature 428, 578) and that there is no need to invoke different cross-bridge step sizes under these different conditions; a step size of 100 Å works well for all loads. We do not claim that this model provides a total mechanical explanation of how muscle works. However, we do suggest that only if there are other observations that cannot be explained by this simple model should something more complicated be considered.

Contemporary Trends in the Philosophy of Life

An issue in philosophy of life is what in nature can and what cannot be explained by physics and chemistry. The mechanical theory is the same as the physico-chemical theory and the mechanical explanation of biological phenomena amounts to the recognition of such phenomena as falling under the laws of physics and chemistry. Hobhouse points out that a living body acts in some respects as a mechanism while in other respects it appears to act differently. But where does the difference lie? One difference seems to be that a living organism, when out of order, struggles back to order and normal functioning in a structured way that a machine appears to be incapable of. Haldane asserts that a living organism can grow from within and give rise to another system of the same sort out of a tiny special itself as it happens in reproduction and that such reproduction belongs to a class qualitatively different from that of mechanical operation. The qualitative difference between life and matter is also supported in Alexander’s doctrine of emergent evolution.

Automata

Automata or “self-moving things” occupy a unique place in Descartes’ worldview. Lacking souls, their internal principle of motion must be accounted for wholly in mechanistic terms. Starting from the form of mechanical explanation engineers use to explain the inner workings of artificial automata—the clocks, mills, and fountain automata of his youthful experience—Descartes proceeds to argue that the same model of explanation is suitable for explaining how animals, plants, and the human body—automata made by God—operate. With these most complex organic systems demystified, Descartes hoped to have demonstrated the universality of mechanism as a science of (non-rational) nature. His recognition of the distinctiveness of such complex systems raises puzzles for what has seemed to many a commitment to a reductionist physics. Automata require special modes of explanation (specifically, functional) and appear to satisfy conditions of identity and persistence that are distinct from those that pertain to the substances composing them. This chapter advances an interpretation according to which Descartes’ notion of true and immutable natures can help to make sense of the special status afforded to automata in his philosophy.

Kleines Lautgesetz, große Wirkung

Zusammenfassung The unexpected i instead of expected *e in the first syllable of Latin wordforms such as nisi, nimis, nihil, mihi, tibi and sibi has until now been explained in various ways either from vowel assimilation of original *e to the i of the second syllable or from clitic weakening of the words. This article aims at giving a common mechanical explanation for all of these words by posing a new sound law according to which original *e in Latin becomes i in initial open syllables followed by a syllable which originally contained the vowel ẹ̄ as the result from monophthongisation of the diphthongs *ei̯, *oi̯or *ai̯(< *h₂ei̯) in second syllable position. For this purpose, the article reconstructs the history of the abovementioned explanations - especially the vowel assimilation theory which goes back to an early article by Sommer -, tries to falsify them by critically examining the evidence adduced for proving them, and eventually derives the new sound law from parts of the original evidence of the falsified explanations, and by making use of additional evidence.