78 resultados para complexity in spatiotemporal evolution


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Over a period of several centuries, the academic study of risk has evolved as a distinct body of thought, which continues to influence conceptual developments in fields such as economics, management, politics and sociology. However, few scholarly works have given a chronological account of cultural and intellectual trends relating to the understanding and analysis of risks. Risk: A Study of its Origins, History and Politics aims to fill this gap by providing a detailed study of key turning points in the evolution of society's understanding of risk. Using a wide range of primary and secondary materials, Matthias Beck and Beth Kewell map the political origins and moral reach of some of the most influential ideas associated with risk and uncertainty at specific periods of time. The historical focus of the book makes it an excellent introduction for readers who wish to go beyond specific risk management techniques and their theoretical underpinnings, to gain an understanding of the history and politics of risk.

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Adaptive Multiple-Input Multiple-Output (MIMO) systems achieve a much higher information rate than conventional fixed schemes due to their ability to adapt their configurations according to the wireless communications environment. However, current adaptive MIMO detection schemes exhibit either low performance (and hence low spectral efficiency) or huge computational
complexity. In particular, whilst deterministic Sphere Decoder (SD) detection schemes are well established for static MIMO systems, exhibiting deterministic parallel structure, low computational complexity and quasi-ML detection performance, there are no corresponding adaptive schemes. This paper solves
this problem, describing a hybrid tree based adaptive modulation detection scheme. Fixed Complexity Sphere Decoding (FSD) and Real-Values FSD (RFSD) are modified and combined into a hybrid scheme exploited at low and medium SNR to provide the highest possible information rate with quasi-ML Bit Error
Rate (BER) performance, while Reduced Complexity RFSD, BChase and Decision Feedback (DFE) schemes are exploited in the high SNR regions. This algorithm provides the facility to balance the detection complexity with BER performance with compatible information rate in dynamic, adaptive MIMO communications
environments.

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This paper analyses some key features of Irish public administration as it has developed since the foundation of the state, paying particular attention to the period from the late 1950s onward. During these decades, notwithstanding successive waves of concern expressed over the need for public sector reform, the evidence suggests an underlying lack of coherence in the evolution of the public administrationsystem that resulted in a poor capacity for effective policy coordination. Yet the drive toward economic modernisation also resulted in the creation of new state competence to support industrial development both directly and indirectly. These changes can be tracked organisationally, drawing on the database of the IRCHSS-funded Mapping the Irish State project.

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Predator–prey interactions are fundamental in the evolution and structure of ecological communities. Our understanding, however, of the strategies used in pursuit and evasion remains limited. Here, we report on the hunting dynamics of the world's fastest land animal, the cheetah, Acinonyx jubatus. Using miniaturized data loggers, we recorded fine-scale movement, speed and acceleration of free-ranging cheetahs to measure how hunting dynamics relate to chasing different sized prey. Cheetahs attained hunting speeds of up to 18.94 m s-1 and accelerated up to 7.5 m s-2 with greatest angular velocities achieved during the terminal phase of the hunt. The interplay between forward and lateral acceleration during chases showed that the total forces involved in speed changes and turning were approximately constant over time but varied with prey type. Thus, rather than a simple maximum speed chase, cheetahs first accelerate to decrease the distance to their prey, before reducing speed 5–8 s from the end of the hunt, so as to facilitate rapid turns to match prey escape tactics, varying the precise strategy according to prey species. Predator and prey thus pit a fine balance of speed against manoeuvring capability in a race for survival.

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As a comparative newly-invented PKM with over-constraints in kinematic chains, the Exechon has attracted extensive attention from the research society. Different from the well-recognized kinematics analysis, the research on the stiffness characteristics of the Exechon still remains as a challenge due to the structural complexity. In order to achieve a thorough understanding of the stiffness characteristics of the Exechon PKM, this paper proposed an analytical kinetostatic model by using the substructure synthesis technique. The whole PKM system is decomposed into a moving platform subsystem, three limb subsystems and a fixed base subsystem, which are connected to each other sequentially through corresponding joints. Each limb body is modeled as a spatial beam with a uniform cross-section constrained by two sets of lumped springs. The equilibrium equation of each individual limb assemblage is derived through finite element formulation and combined with that of the moving platform derived with Newtonian method to construct the governing kinetostatic equations of the system after introducing the deformation compatibility conditions between the moving platform and the limbs. By extracting the 6 x 6 block matrix from the inversion of the governing compliance matrix, the stiffness of the moving platform is formulated. The computation for the stiffness of the Exechon PKM at a typical configuration as well as throughout the workspace is carried out in a quick manner with a piece-by-piece partition algorithm. The numerical simulations reveal a strong position-dependency of the PKM's stiffness in that it is symmetric relative to a work plane due to structural features. At the last stage, the effects of some design variables such as structural, dimensional and stiffness parameters on system rigidity are investigated with the purpose of providing useful information for the structural optimization and performance enhancement of the Exechon PKM. It is worthy mentioning that the proposed methodology of stiffness modeling in this paper can also be applied to other overconstrained PKMs and can evaluate the global rigidity over workplace efficiently with minor revisions.

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Background and Aims: Although hybridization can play a positive role in plant evolution, it has been shown that excessive unidirectional hybridization can result in replacement of a species’ gene pool, and even the extinction ofrare species via genetic assimilation. This study examines levels of introgression between the common Saxifraga spathularis and its rarer congener S. hirsuta, which have been observed to hybridize in the wild where they occursympatrically. 
Methods: Seven species-specific single nucleotide polymorphisms (SNPs) were analysed in 1025 plants representing both species and their hybrid, S. polita, from 29 sites across their ranges in Ireland. In addition, species distributionmodelling was carried out to determine whether the relative abundance of the two parental species is likely to change under future climate scenarios. 
Key Results: Saxifraga spathularis individuals tended to be genetically pure, exhibiting little or no introgression from S. hirsuta, but significant levels of introgression of S. spathularis alleles into S. hirsuta were observed, indicatingthat populations exhibiting S. hirsuta morphology are more like a hybrid swarm, consisting of backcrosses and F2s. Populations of the hybrid, S. polita, were generally comprised of F1s or F2s, with some evidence of backcrossing. Species distribution modelling under projected future climate scenarios indicated an increase in suitable habitats for both parental species.
Conclusions: Levels of introgression observed in this study in both S. spathularis and S. hirsuta would appear to be correlated with the relative abundance of the species. Significant introgression of S. spathularis alleles was detectedin the majority of the S. hirsuta populations analysed and, consequently, ongoing introgression would appear to represent a threat to the genetic integrity of S. hirsuta, particularly in areas where the species exists sympatricallywith its congener and where it is greatly outnumbered.

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The principle feature in the evolution of the internet has been its ever growing reach to include old and young, rich and poor. The internet’s ever encroaching presence has transported it from our desktop to our pocket and into our glasses. This is illustrated in the Internet Society Questionnaire on Multistakeholder Governance, which found the main factors affecting change in the Internet governance landscape were more users online from more countries and the influence of the internet over daily life. The omnipresence of the internet is self- perpetuating; its usefulness grows with every new user and every new piece of data uploaded. The advent of social media and the creation of a virtual presence for each of us, even when we are not physically present or ‘logged on’, means we are fast approaching the point where we are all connected, to everyone else, all the time. We have moved far beyond the point where governments can claim to represent our views which evolve constantly rather than being measured in electoral cycles.
The shift, which has seen citizens as creators of content rather than consumers of it, has undermined the centralist view of democracy and created an environment of wiki democracy or crowd sourced democracy. This is at the heart of what is generally known as Web 2.0, and widely considered to be a positive, democratising force. However, we argue, there are worrying elements here too. Government does not always deliver on the promise of the networked society as it involves citizens and others in the process of government. Also a number of key internet companies have emerged as powerful intermediaries harnessing the efforts of the many, and re- using and re-selling the products and data of content providers in the Web 2.0 environment. A discourse about openness and transparency has been offered as a democratising rationale but much of this masks an uneven relationship where the value of online activity flows not to the creators of content but to those who own the channels of communication and the metadata that they produce.
In this context the state is just one stakeholder in the mix of influencers and opinion formers impacting on our behaviours, and indeed our ideas of what is public. The question of what it means to create or own something, and how all these new relationships to be ordered and governed are subject to fundamental change. While government can often appear slow, unwieldy and even irrelevant in much of this context, there remains a need for some sort of political control to deal with the challenges that technology creates but cannot by itself control. In order for the internet to continue to evolve successfully both technically and socially it is critical that the multistakeholder nature of internet governance be understood and acknowledged, and perhaps to an extent, re- balanced. Stakeholders can no longer be classified in the broad headings of government, private sector and civil society, and their roles seen as some sort of benign and open co-production. Each user of the internet has a stake in its efficacy and each by their presence and participation is contributing to the experience, positive or negative of other users as well as to the commercial success or otherwise of various online service providers. However stakeholders have neither an equal role nor an equal share. The unequal relationship between the providers of content and those who simple package up and transmit that content - while harvesting the valuable data thus produced - needs to be addressed. Arguably this suggests a role for government that involves it moving beyond simply celebrating and facilitating the on- going technological revolution. This paper reviews the shifting landscape of stakeholders and their contribution to the efficacy of the internet. It will look to critically evaluate the primacy of the individual as the key stakeholder and their supposed developing empowerment within the ever growing sea of data. It also looks at the role of individuals in wider governance roles. Governments in a number of jurisdictions have sought to engage, consult or empower citizens through technology but in general these attempts have had little appeal. Citizens have been too busy engaging, consulting and empowering each other to pay much attention to what their governments are up to. George Orwell’s view of the future has not come to pass; in fact the internet has insured the opposite scenario has come to pass. There is no big brother but we are all looking over each other’s shoulder all the time, while at the same time a number of big corporations are capturing and selling all this collective endeavour back to us.

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A complete nucleotide sequence of the new Pseudomonas aeruginosa Luz24likevirus phiCHU was obtained. This virus was shown to have a unique host range whereby it grew poorly on the standard laboratory strain PAO1, but infected 26 of 46 clinical isolates screened, and strains harboring IncP2 plasmid pMG53. It was demonstrated that phiCHU has single strand interruptions in its genome. Analysis of the phiCHU genome also suggested that recombination event(s) participated in the evolution of the leftmost portion of the genome, presumably encoding early genes.

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Amphibian skin secretion has great potential for drug discovery and contributes hundreds of bioactive peptides including bradykinin-related peptides (BRPs). More than 50 BRPs have been reported in the last two decades arising from the skin secretion of amphibian species. They belong to the families Ascaphidae (1 species), Bombinatoridae (3 species), Hylidae (9 speices) and Ranidae (25 species). This paper presents the diversity of structural characteristics of BRPs with N-terminal, C-terminal extension and amino acid substitution. The further comparison of cDNA-encoded prepropeptides between the different species and families demonstrated that there are various forms of kininogen precursors to release BRPs and they constitute important evidence in amphibian evolution. The pharmacological activities of isolated BRPs exhibited unclear structure–function relationships, and therefore the scope for drug discovery and development is limited. However, their diversity shows new insights into biotechnological applications and, as a result, comprehensive and systematic studies of the physiological and pharmacological activities of BRPs from amphibian skin secretion are needed in the future.

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This paper proposes an efficient learning mechanism to build fuzzy rule-based systems through the construction of sparse least-squares support vector machines (LS-SVMs). In addition to the significantly reduced computational complexity in model training, the resultant LS-SVM-based fuzzy system is sparser while offers satisfactory generalization capability over unseen data. It is well known that the LS-SVMs have their computational advantage over conventional SVMs in the model training process; however, the model sparseness is lost, which is the main drawback of LS-SVMs. This is an open problem for the LS-SVMs. To tackle the nonsparseness issue, a new regression alternative to the Lagrangian solution for the LS-SVM is first presented. A novel efficient learning mechanism is then proposed in this paper to extract a sparse set of support vectors for generating fuzzy IF-THEN rules. This novel mechanism works in a stepwise subset selection manner, including a forward expansion phase and a backward exclusion phase in each selection step. The implementation of the algorithm is computationally very efficient due to the introduction of a few key techniques to avoid the matrix inverse operations to accelerate the training process. The computational efficiency is also confirmed by detailed computational complexity analysis. As a result, the proposed approach is not only able to achieve the sparseness of the resultant LS-SVM-based fuzzy systems but significantly reduces the amount of computational effort in model training as well. Three experimental examples are presented to demonstrate the effectiveness and efficiency of the proposed learning mechanism and the sparseness of the obtained LS-SVM-based fuzzy systems, in comparison with other SVM-based learning techniques.

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During recent years, news headlines have been rife with criticisms of the risk management practices of public and private sector entities. These criticisms have often been accompanied by calls for greater transparency in the way government entities manage risks and communicate dangers to the public. Similarly, in the private sector, the internationalisation of economic activity has heightened concerns over the potential adverse implications of mismanagement and financial scandals, and has led to calls for greater regulation and supervision. While the responses of public sector agencies and private sector actors to these challenges have differed, they share a common acknowledgement that effective governance relies on the pro-active identification, assessment, and management of risks as well as appropriate regulatory frameworks.

This edited book covers a number of divergent topics illustrating the emergence of several novel themes in the area of economic and social risks. As a communality, these novel themes relate to the complexity in which human activity in this late stage of capitalist development is embedded. This risk-generating complexity, in turn, can be observed at several levels, including workplace hazards, governance problems within the private sector or the intersection between public and private, and in relation to the economic risks faced by larger entities such as national governments.

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Microbial communities are enigmatically diverse. We propose a novel view of processes likely affecting microbial assemblages, which could be viewed as the Great American Interchange en miniature: the wholesale exchange among microbial communities resulting from moving pieces of the environment containing entire assemblages. Incidental evidence for such ‘community coalescence’ is accumulating, but such processes are rarely studied, likely because of the absence of suitable terminology or a conceptual framework. We provide the nucleus for such a conceptual foundation for the study of community coalescence, examining factors shaping these events, links to bodies of ecological theory, and we suggest modeling approaches for understanding coalescent communities. We argue for the systematic study of community coalescence because of important functional and applied consequences.