515 research outputs found

    Are Critical Phenomena Relevant to Large-Scale Evolution?

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    Recent theoretical studies, based on the theory of self-organized critical systems, seem to suggest that the dynamical patterns of macroevolution could belong to such class of critical phenomena. Two basic approaches have been proposed: the Kauffman-Johnsen model (based on the use of coupled fitness landscapes) and the Bak-Sneppen model. Both are reviewed here. These models are oversimplified pictures of biological evolution, but the (possible) validity of them is based on the concept of universality, i.e. that apparently very different systems sharing some few common properties should also behave in a very similar way. In this paper we explore the current evidence from the fossil record, showing that some properties that are suggestive of critical dynamics would also be the result of random phenomema. Some general properties of the large-scale pattern of evolution, which should be reproduced by these models, are discussed.Peer reviewe

    Thermography imaging during static and controlled thermoregulation in complex regional pain syndrome type 1: diagnostic value and involvement of the central sympathetic system

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    BACKGROUND: Complex Regional Pain Syndrome type 1 (CRPS1) is a clinical diagnosis based on criteria describing symptoms of the disease. The main aim of the present study was to compare the sensitivity and specificity of calculation methods used to assess thermographic images (infrared imaging) obtained during temperature provocation. The secondary objective was to obtain information about the involvement of the sympathetic system in CRPS1. METHODS: We studied 12 patients in whom CRPS1 was diagnosed according to the criteria of Bruehl. High and low whole body cooling and warming induced and reduced sympathetic vasoconstrictor activity. The degree of vasoconstrictor activity in both hands was monitored using a videothermograph. The sensitivity and specificity of the calculation methods used to assess the thermographic images were calculated. RESULTS: The temperature difference between the hands in the CRPS patients increases significantly when the sympathetic system is provoked. At both the maximum and minimum vasoconstriction no significant differences were found in fingertip temperatures between both hands. CONCLUSION: The majority of CRPS1 patients do not show maximal obtainable temperature differences between the involved and contralateral extremity at room temperature (static measurement). During cold and warm temperature challenges this temperature difference increases significantly. As a result a higher sensitivity and specificity could be achieved in the diagnosis of CRPS1. These findings suggest that the sympathetic efferent system is involved in CRPS1

    Narrating China’s Belt and Road Initiative

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    This article studies the formation process of China's belt and road initiative (BRI) – the most important Chinese foreign policy initiative under Xi Jinping. It argues that the BRI was put forward as a broad policy idea that was subsequently developed with relatively concrete content. During this process, the shifting international landscapes have gradually driven the BRI from a periphery strategy into a global initiative. By examining the case of Jiangsu Province, this article also shows how Chinese local governments have actively deployed their preferred narratives to influence and (re‐)interpret the BRI guidelines of the central government in order to advance their own interests. As a result, this produces a variety of competing, ambiguous and contradictory policy narratives of the BRI within China, which undermines the Chinese central government's monopoly on the BRI narratives. This leaves the BRI as a very vague and broad policy slogan that is subject to change and open to interpretation. In this regard, the existing analyses – that consider the BRI as Beijing's masterplan to achieve its geopolitical goals – pay insufficient attention to the BRI's domestic contestation and overstate the BRI's geopolitical implications

    Never Resting Brain: Simultaneous Representation of Two Alpha Related Processes in Humans

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    Brain activity is continuously modulated, even at “rest”. The alpha rhythm (8–12 Hz) has been known as the hallmark of the brain's idle-state. However, it is still debated if the alpha rhythm reflects synchronization in a distributed network or focal generator and whether it occurs spontaneously or is driven by a stimulus. This EEG/fMRI study aimed to explore the source of alpha modulations and their distribution in the resting brain. By serendipity, while computing the individually defined power modulations of the alpha-band, two simultaneously occurring components of these modulations were found. An ‘induced alpha’ that was correlated with the paradigm (eyes open/ eyes closed), and a ‘spontaneous alpha’ that was on-going and unrelated to the paradigm. These alpha components when used as regressors for BOLD activation revealed two segregated activation maps: the ‘induced map’ included left lateral temporal cortical regions and the hippocampus; the ‘spontaneous map’ included prefrontal cortical regions and the thalamus. Our combined fMRI/EEG approach allowed to computationally untangle two parallel patterns of alpha modulations and underpin their anatomical basis in the human brain. These findings suggest that the human alpha rhythm represents at least two simultaneously occurring processes which characterize the ‘resting brain’; one is related to expected change in sensory information, while the other is endogenous and independent of stimulus change

    China’s Artificial Intelligence Innovation:A Top-Down National Command Approach?

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    China’s open embracing of the age of artificial intelligence (AI) has attracted considerable academic and media attention. Many argue that China has taken advantage of its national approach to contest for AI supremacy and geopolitical dominance. The relevant analyses assume China’s AI plans as being Beijing’s coherent top‐down geopolitically driven national strategy, reflecting Chinese leaders’ global ambitions. This article argues that these views are mistaken. It argues that China’s AI plans are primarily driven by contestation and the struggle for resources among domestic stakeholders who are economically motivated and have little awareness of the bigger geopolitical picture. Instead of a top‐down command approach, China’s national AI plan is an upgrade of existing local AI initiatives to the national level, reflecting a bottom‐up development. This article suggests that the existing analyses vastly exaggerate: (1) Beijing’s capacity to coordinate domestic capital and actors towards a unified, specific strategic objective; and (2) the extent of China’s AI advancement and its geopolitical threat, triggering unnecessary anxiety among China’s near competitors
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