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1.
Geodesy—the determination of the size and shape of the earth—has often been the science operating at the frontier of precision in the measurement of length. Its contribution to the technologies and standards of length measurement has, however, been underestimated in the literature. That, instead, places emphasis on the on the creation and international acceptance of the metric system as a whole. By new research into the standards-in-use of the community of geodesists, I rediscover the original purpose of the Metre Convention of 1875, and show for the first time the significant influence of geodesy on the standardisation of length measurement thereafter. I emphasise the role of the coherence of the web of measurement in the context of change and improvement in standards.  相似文献   

2.
I explain Locke’s account of the origin of our idea of power, showing that it concerns the idea of the disposition to act or change, and that this idea is constructed out of the ideas of action or change. I also show how Locke could have modified his account to avoid Hume’s criticism and argue that his neglect to do so reflects a studied neglect of taxonomy, an ambiguity in the notion of capacity, and complications in Locke’s conception of simple ideas. A comparison of the two empiricists reveals that not only do they disagree about the role of reason in the origin of our idea of power, but they are also talking about different ideas. Within the framework of Locke’s account of the origin of the idea of power, I explain why he believes that bodies only provide us with an obscure idea of active power. I conclude by defending his insight that there is a deep connection between the ability to predict and the idea of power.  相似文献   

3.
Kant’s transcendental method, as applied to natural philosophy, considers the laws of physics as conditions of the possibility of experience. A more modest transcendental project is to show how the laws of motion explicate the concepts of motion, force, and causal interaction, as conditions of the possibility of an objective account of nature. This paper argues that such a project is central to the natural philosophy of Newton, and explains some central aspects of the development of his thinking as he wrote the Principia. One guiding scientific aim was the dynamical analysis of any system of interacting bodies, and in particular our solar system; the transcendental question was, what are the conceptual prerequisites for such an analysis? More specifically, what are the conditions for determining “true motions” within such a system—for posing the question of “the frame of the system of the world” as an empirical question? A study of the development of Newton’s approach to these questions reveals surprising connections with his developing conceptions of force, causality, and the relativity of motion. It also illuminates the comparison between his use of the transcendental method and that of Euler and Kant.  相似文献   

4.
B Surawicz 《Experientia》1987,43(10):1061-1068
The understanding of cardiac action potential and membrane currents has broadened the theoretical foundation and enhanced the clinical usefulness of the electrocardiogram. An improved understanding of the morphology of the electrocardiographic waveform has resulted from: correlations between Vmax of depolarization and QRS complex, plateau of the ventricular action potential and S-T segment, terminal repolarization and T-wave, from definitions of action potential differences responsible for the T-wave, and recordings of action potential alternans. Cellular electrophysiology has contributed to the understanding of certain mechanisms of cardiac standstill. Many disturbances of conduction and refractoriness associated with ventricular arrhythmias can be attributed to the following derangements at the cellular level: slowing of terminal repolarization, development of diastolic depolarization in fibers with stable resting membrane potential, after-depolarizations, currents of injury resulting from non-uniform polarization, increased dispersion of action potential durations, and co-existence of slow conduction and short premature action potentials.  相似文献   

5.
Summary The diffraction of electrons, based on the theories of undulatory mechanics (Louis de Broglie), has grown now to a method of investigation into the structure of matter, complementing the analysis by X-rays and electronic microscopy.Its use is developing every day in the most heterogeneous fields: study of crystalline structures, of metallic layers, of oxidation, corrosion, adsorption, catalysis, of polishing and of the conditions of superficies, as also of lubrication and of isolated molecules, etc.The article gives some instances of the diverse applications.  相似文献   

6.
We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.  相似文献   

7.
    
Summary Experiments performed on dogs show that the very active anticholinesterase diisopropylfluorophosphate (DFD) does not affect either the cardiovascular and respiratory reflexes of carotid sinus origin or the peripheral excitability of the heart vagus nerve. Injection of prostigmine after administration of DFP and previous complete inhibition of the cholinesterases, still induces a slowing of the heart, an increase of vagal excitability, an increase of the peristaltic movements of the intestines and a bronchospasm. These experiments thus do not support the theory of a central or peripheral cholinergic transmission of the cardiovascular and respiratory reflexes induced by stimulation of the carotid sinus pressoceptors. These experiments also show that several pharmacological actions of prostigmine are not related to the anticholinesterase action of this drug.  相似文献   

8.
This paper investigates the historical origins of the notion of incommensurability in contemporary philosophy of science. The aim is not to establish claims of priority, but to enhance our understanding of the notion by illuminating the various issues that contributed to its development. Kuhn developed his notion of incommensurability primarily under the influence of Fleck, Polanyi, and Köhler. Feyerabend, who had developed his notion more than a decade earlier, drew directly from Duhem, who had developed a notion of incommensurability in 1906. The idea is that in the course of scientific advance, when fundamental theories change, meanings change, which can result in a new conception of the nature of reality. Feyerabend repeatedly used this notion of incommensurability to attack various forms of conceptual conservativism. These include the logical positivists’ foundational use of protocol statements, Heisenberg’s methodological principle that established results must be presupposed by all further research, attempts to separate philosophical accounts of ontology from physics, Bohr’s principle of complementarity, and logical empiricist accounts of reduction and explanation. Focusing on the function of the notion of incommensurability common to Feyerabend’s various critiques explicates Feyerabend’s early philosophy as a series of challenges to forms of conceptual conservativism.  相似文献   

9.
10.
Fibrosis is a pathological form of aberrant tissue repair, the complications of which account for nearly half of all deaths in the industrialized world. All tissues are susceptible to fibrosis under particular pathological sets of conditions. Though each type of fibrosis has characteristics and hallmarks specific to that particular condition, there appear to be common factors underlying fibrotic diseases. One of these ubiquitous factors is the paradigm of the activated myofibroblast in the promotion of fibrotic phenotypes. Recent research has implicated metabolic byproducts of the amino acid tryptophan, namely serotonin and kynurenines, in the pathology or potential pharmacologic therapy of fibrosis, in part through their effects on development of myofibroblast phenotypes. Here, we review literature underlying what is known mechanistically about the effects of these compounds and their respective pathways on fibrosis. Pharmacologic administration of kynurenine improves scarring outcomes in vivo likely not only through its well-characterized immunosuppressive properties but also via its demonstrated antagonism of fibroblast activation and of collagen deposition. In contrast, serotonin directly promotes activation of fibroblasts via activation of canonical TGF-β signaling, and overstimulation with serotonin leads to fibrotic outcomes in vivo. Recently discovered feedback inhibition between serotonin and kynurenine pathways also reveals more information about the cellular physiology of tryptophan metabolism and may also underlie possible paradigms for anti-fibrotic therapy. Together, understanding of the effects of tryptophan metabolism on modulation of fibrosis may lead to the development of new therapeutic avenues for treatment through exploitation of these effects.  相似文献   

11.
This paper advocates the reduction of the inference of common cause to that of common origins. It distinguishes and subjects to critical analysis thirteen interpretations of “the inference of common cause” whose conclusions do not follow from their assumptions. Instead, I introduce six types of inferences of common origins of information signals from their receivers to reduce, in the sense of supersede and replace, the thirteen inferences of common causes. I show how the paradigmatic examples of inferences of common cause, as well as a broader scope of inferences in the historical sciences, are better explained by inferences of origins.Inferences of origins from information rich coherences between receivers of information signals both fit more closely and explain better the range of examples that have traditionally been associated with inferences of common causes, as well as a broader scope of examples from the historical sciences. Shannon's concept of information as reduction in uncertainty, rather than physicalist concepts of information that relate it to entropy or waves, simplifies the inferences, preempts objections, and avoids the underdetermination of conclusions that challenge models of inferences of common causes.In the second part of the paper I model inferences of common origins from information preserved in their receivers. I distinguish information poor inferences that there were some common origins of receivers from the information richer inferences of ranges of possible common origins and the information transmission channels by which they transmitted signals to receivers. Lastly and most information rich, I distinguish the inference of the defining properties of common origins. The information transmission model from origins to receivers allows the reconceptualization of the concepts of "independence" as absence of intersections between information channels and "reliability" as the preservation of information from origins in receivers. Finally, I show how inferences of origins form the epistemic basis of the historical sciences.  相似文献   

12.
Summary Urethane produces a level of surgical anesthesia characterized by preservation of a number of cardiovascular reflexes. When the proper route of administration is used, and the use of unnecessarily high doses is avoided, urethane anesthesia appears to be suitable for a number of investigations at cardiovascular level. However in certain types of studies involving pharmacological stimulation of peripheral adrenoceptors urethane affects markedly the magnitude of the response under study.  相似文献   

13.
    
Summary Velocity of combustion of elements is expressed as an inverse function of initial mass (of hydrogene) wherein the chain of formation of elements begins. The solar system is considered as a homogenous unity and evaluation of the rate of elements heavier thanH andHe is attempted for planets such as Jupiter by means of linear relation established on the basis of data concerning sun and earth.  相似文献   

14.
This paper argues for a novel way of addressing questions about the relationship between politics and science: in terms of norms of communication, rather than norms of cognition. The first half of the paper motivates this general shift through close study of the concept of "wishful speaking"; arguing that this vice - rather than the more familiar "wishful thinking" - better captures real-life cases, such as the Lysenko affair. The second half builds on the ethics of communication to develop an account of the proper role of non-epistemic values in justification in terms of "value-aptness".  相似文献   

15.
Summary Prolonged administration of a vitamin E deficient die to Wistar rats resulted in regressive changes in granular pericytes distributed around fine vessels of the cerebral cortex. The regressive signs included expansion of endoplasmic reticula, swelling of mitochondria and increase of vesicular structures. Rupture of the limiting membranes of the intracellular granules often accompanied these changes. The finding seems important for an understanding of the physiology and nutriology of granular pericytes in the brain.This study was supported in part by a grant in aid for Scientific Research from the Ministry of Education of Japan (No. 448085).  相似文献   

16.
17.
企业核心能力与企业综合竞争能力是两个不同的概念,对二者进行评判、识别和诊断的方法也不尽相同,但现有关于企业核心能力评判的研究,普遍借用了企业综合竞争力评价的方法和体系,从而使研究的结论过于宽泛,可操作性不强。本文从企业核心能力与企业竞争力的内涵差别出发,辨析了二者研究的差弄,指出了企业核心能力评判研究的特点、方法及其现实意义。  相似文献   

18.
The insulin-like growth factor (IGF) axis is a multicomponent molecular network which has important biological functions in the development and maintenance of differentiated tissue function(s). One of the most important functions of the IGF axis is the control of skeletal tissue metabolism by the finely tuned regulation of the process of osteogenesis. To achieve this, the IGF axis controls the activity of several cell types—osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts to achieve the co-ordinated development of appropriate hard tissue structure and associated matrix deposition. In addition, there is an increasing awareness that the IGF axis also plays a role in the process of odontogenesis (tooth formation). In this review, we highlight some of the key findings in both of these areas. A further understanding of the role of the IGF axis in hard tissue biology may contribute to tissue regeneration strategies in cases of skeletal tissue trauma.  相似文献   

19.
The sensitivity of dopamine receptors in Mouse striatum has been evaluated both behaviourally (responsiveness to apomorphine as regarviour) and biochemically (striatal level of homovanillic acid and its decrease induced by apomorphine) After a single administration of apomorphine (0.25 mg.kg-1 or 5 mg.kg-1) or piribedil, another dopamine agonist, a state of "behavioural facilitation" develops which differs from the state of hypersensitivity following blockade. This state of facilitation is characterized by a lower threshold dose of apomorphine eliciting the stereotyped behaviour, without modification of the response to higher doses. In contrast with the state of hypersensitivity, the level of homovanillic acid is not modified and the decrease of this level by a low dose of apomorphine is less important. The hypothesis is put forward that "behavioural facilitation" results from the hyposensitivity of a class of dopamine receptors, possibly autoreceptors, mediating an impaired activity of dopaminergic neurons and, consequently, inhibitory behavioural effects.  相似文献   

20.
The neurotoxins produced by various species of Clostridia are the causative agents of botulism and tetanus. The ability of the toxins, specifically those of the botulinum neurotoxin family, to disrupt neurotransmission has been exploited for use in several medical indications and now represents the therapeutic option of choice in a number of cases. Clostridial neurotoxins have been discovered to have a multi-domain structure that is shared between the various proteins of the family, and it has also been determined that each domain contributes a specific role to the holotoxin. The extensive use of recombinant expression approaches, along with solution of multiple crystallographic structures of individual domains, has enabled researchers to explore structurefunction relationships of the toxin domains more closely. These advances have facilitated a greater understanding of the potential use of individual domains for a wide variety of purposes, including the development of new therapeutics. Received 21 October 2005; received after revision 10 November 2005; accepted 16 November 2005  相似文献   

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