44 resultados para Complex biological systems


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Long-distance migrations are among the wonders of the natural world, but this multi-taxon review shows that the characteristics of species that undertake such movements appear to make them particularly vulnerable to detrimental impacts of climate change. Migrants are key components of biological systems in high latitude regions, where the speed and magnitude of climate change impacts are greatest. They also rely on highly productive seasonal habitats, including wetlands and ocean upwellings that, with climate change, may become less food-rich and predictable in space and time. While migrants are adapted to adjust their behaviour with annual changes in the weather, the decoupling of climatic variables between geographically separate breeding and non-breeding grounds is beginning to result in mistimed migration. Furthermore, human land-use and activity patterns will constrain the ability of many species to modify their migratory routes and may increase the stress induced by climate change. Adapting conservation strategies for migrants in the light of climate change will require substantial shifts in site designation policies, flexibility of management strategies and the integration of forward planning for both people and wildlife. While adaptation to changes may be feasible for some terrestrial systems, wildlife in the marine ecosystem may be more dependent on the degree of climate change mitigation that is achievable.

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Mounting evidence indicates that schizophrenia is associated with adverse intrauterine experiences. An adverse or suboptimal fetal environment can cause irreversible changes in brain that can subsequently exert long-lasting effects through resetting a diverse array of biological systems including endocrine, immune and nervous. It is evident from animal and imaging studies that subtle variations in the intrauterine environment can cause recognizable differences in brain structure and cognitive functions in the offspring. A wide variety of environmental factors may play a role in precipitating the emergent developmental dysregulation and the consequent evolution of psychiatric traits in early adulthood by inducing inflammatory, oxidative and nitrosative stress (IO&NS) pathways, mitochondrial dysfunction, apoptosis, and epigenetic dysregulation. However, the precise mechanisms behind such relationships and the specificity of the risk factors for schizophrenia remain exploratory. Considering the paucity of knowledge on fetal programming of schizophrenia, it is timely to consolidate the recent advances in the field and put forward an integrated overview of the mechanisms associated with fetal origin of schizophrenia.

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 Increasing attention is paid to organisational learning, with the success of contemporary organisations strongly contingent on their ability to learn and grow. Importantly, informal learning is argued to be even more significant than formal learning initiatives. Given the widespread use of digital technologies in the workplace, what requires further attention is how digital technologies (eg, massive open online courses—MOOC) enable informal learning processes. Drawing from Complex Adaptive Systems (CAS) theory, in this paper we advance a conceptual model for examining this important topic. The two dimensional matrix and the micro-level description of informal learning activities presented provide a framework for both further research on technology-mediated practices for informal learning, as well as the design of formative contexts for learning to occur.

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This chapter seeks to delve deeper into the ancient history of democracy than is normally permitted, back to a time preceding the developments of classical Athens, when the earliest signs of organized society and complex governmental systems emerged across the ancient Middle East. It then seeks to compare and contrast these ancient Middle Eastern examples with those of classical Athens and to offer new insights into, and questions about, the nature and history of democracy. Building on some recent work (Fleming, 2004; Isakhan, 2007a; Keane, 2009: 78–155), this chapter also hopes to move the discussion beyond the phrase usually associated with ancient Middle Eastern democracies, that of ‘primitive democracy’. This chapter also argues that, while the Middle Eastern experiments were less rigid and formalized, they were in no measurable sense more ‘primitive’ than the later example offered by classical Athens. However, this essay also cautiously notes that, while not all of the elements which made ancient Athens significant occurred in the same way and at the same time in the ancient Middle East, all of them did exist at varying times and in varying guises across these earlier civilizations. To demonstrate this thesis, the remainder of the chapter utilizes several of the key criteria by which we commonly measure Athenian democracy – the functioning of its assembly, the mechanisms of justice and of the law, the varying voting and elective procedures, the rights and freedoms of the citizens, and the systematic exclusion of ‘non-citizens’ – and discusses precedents and parallels drawn from the extant evidence concerning the ancient Middle East.

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Advances in high-throughput, comprehensive small molecule analytical techniques have seen the development of the field of metabolomics. The coupling of mass spectrometry with high-resolution chromatography provides extensive chemical profiles from complex biological extracts. These profiles include thousands of compounds linked to gene expression, and can be used as taxonomic characters. Studies have shown metabolite profiles to be taxon specific in a range of organisms, but few have investigated taxonomically problematic plant taxa. This study used a phenetic analysis of metabolite profiles to test taxonomic boundaries in the Olearia phlogopappa (Asteraceae) complex as delimited by morphological data. Metabolite profiles were generated from both field- and shade house-grown material, using liquid chromatography-mass spectrometry (LC-MS). Aligned profiles of 51 samples from 12 taxa gave a final dataset of over 10,000 features. Multivariate analyses of field and shade house material gave congruent results, both confirming the distinctiveness of the morphologically defined species and subspecies in this complex. Metabolomics has great potential in alpha taxonomy, especially for testing the boundaries of closely related taxa where DNA sequence data has been uninformative.

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Ageing is a complex biological process for which underlying biochemical changes are still largely unknown. We performed comparative profiling of the cellular proteome and metabolome to understand the molecular basis of ageing in Caspase-2-deficient (Casp2(-/-)) mice that are a model of premature ageing in the absence of overt disease. Age-related changes were determined in the liver and serum of young (6-9 week) and aged (18-24 month) wild-type and Casp2(-/-) mice. We identified perturbed metabolic pathways, decreased levels of ribosomal and respiratory complex proteins and altered mitochondrial function that contribute to premature ageing in the Casp2(-/-) mice. We show that the metabolic profile changes in the young Casp2(-/-) mice resemble those found in aged wild-type mice. Intriguingly, aged Casp2(-/-) mice were found to have reduced blood glucose and improved glucose tolerance. These results demonstrate an important role for caspase-2 in regulating proteome and metabolome remodelling during ageing.

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A reliable description of ion pair interactions for biological systems, particularly those involving polyatomic ions such as carboxylate and divalent ions such as Ca2+, using biomolecular force-fields is essential for making useful predictions for a range of protein functions. In particular, the interaction of divalent ions with the double carboxylate group present in γ-carboxyglutamic acid (Gla), relevant to the function of many proteins, is relatively understudied using biomolecular force-fields. Using force-field based metadynamics simulations to predict the free energy of binding between Ca2+ and the carboxylate group in liquid water, we show that a widely-used biomolecular force-field, CHARMM22∗, substantially over-estimates the binding strength between Ca2+ and the side-chains of both glutamic acid (Glu) and Gla, compared with experimental data obtained for the analogous systems of aqueous calcium-acetate and calcium-malonate. To correct for this, we propose and test a range of modifications to the σ value of the heteroatomic Lennard-Jones interaction between Ca2+ and the oxygen of the carboxylate group. Our revised parameter set can recover the same three association modes of this aqueous ion pair as the standard parameter set, and yields free energies of binding for the carboxylate-Ca2+ interaction in good agreement with experimental data. The revised parameter set recovers other structural properties of the ion pair in agreement with the standard CHARMM22∗ parameter set.

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Regenerated Bombyx mori (B. mori) silk fibroin is a type of widely used biomaterial. The β-sheet structure of it after methanol treatment provides water-insolubility and mechanical stability while on the other side leads to a hydrophobic surface which is less preferred by biological systems. In this work we prepare a novel type of nanoconfined silk fibroin film with a thickness below 100 nm. The film has a flat while hydrophobic surface because of its β-sheet structure due to the z-direction confinement during formation. Different types of lipid monolayers, DOPC, DPPC and MO, are assembled on the silk film surface. The lipid coating, especially the DPPC membrane, provides a much smoother and more hydrophilic surface due to the gel phase tails of the lipids, in comparison with the DOPC and MO ones which are in a liquid phase and have a much stronger interfacial association between silk film surface and lipid tails. Such a lipid coating preserves the biocompatibility and cellular affinity of the silk film which promises potential applications as surface coatings for materials for biological use.

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The adoption of Building Information Modelling (BIM) is one of the greatest technological innovations in the construction industry to date. However, the implementation of BIM lags far behind its potential due to the existence of various barriers. Strong government support is critical for the successful development and deployment of complex technology systems. BIM could seek government support to drive its implementation process and overcome the barriers. Through a survey, this paper aims to discover stakeholders’ expectations of the government role in BIM implementation and explores specific ways for governments to promote BIM implementation. The research findings are expected to assist related departments to accelerate BIM implementation.

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In cloud environments, IT solutions are delivered to users via shared infrastructure. One consequence of this model is that large cloud data centres consume large amounts of energy and produce significant carbon footprints. A key objective of cloud providers is thus to develop resource provisioning and management solutions at minimum energy consumption while still guaranteeing Service Level Agreements (SLAs). However, a thorough understanding of both system performance and energy consumption patterns in complex cloud systems is imperative to achieve a balance of energy efficiency and acceptable performance. In this paper, we present StressCloud, a performance and energy consumption analysis tool for cloud systems. StressCloud can automatically generate load tests and profile system performance and energy consumption data. Using StressCloud, we have conducted extensive experiments to profile and analyse system performance and energy consumption with different types and mixes of runtime tasks. We collected finegrained energy consumption and performance data with different resource allocation strategies, system configurations and workloads. The experimental results show the correlation coefficients of energy consumption, system resource allocation strategies and workload, as well as the performance of the cloud applications. Our results can be used to guide the design and deployment of cloud applications to balance energy and performance requirements.

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The application of mesoporous silica nanoparticles (MSNs) as a smart delivery system to agricultural crops is gaining attention but the release of nanoparticles into the environment may pose a potential threat to biological systems. We investigated the effects of MSNs on the growth and development of wheat and lupin plants grown under controlled conditions. We report a dramatic increase in the growth of wheat and lupin plants exposed to MSNs. We also found that, in leaves, MSNs localised to chloroplasts and that photosynthetic activity was significantly increased. In addition, absorption and cellular distribution of MSNs by the two plant species following root uptake were observed using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). Following uptake of MSNs at 500 and 1000 mg L(-1), there was enhancement of seed germination, increased plant biomass, total protein and chlorophyll content. Treatment of both species with MSNs at the highest concentration (2000 mg L(-1)) did not result in oxidative stress or cell membrane damage. These findings show that MSNs can be used as novel delivery systems in plants and that over the range of concentrations tested, MSNs do not have any negative impacts on plant growth or development.

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Workflow applications require workflow processing in which workflow tasks are processed based on their dependencies. With the emergency of complex distributed systems such as grids and clouds, efficient workflow scheduling (WFS) algorithms have become the core components of the workflow management systems (WfMS). Thus, WFS that allocates each task in the workflow to a relevant resource with the aim of improving system performance and end user satisfaction is fundamentally important. In this paper, we propose a new workflow scheduling algorithm called Layered Workflow Scheduling Algorithm (LWFS) for scheduling workflow applications. We studied the efficacy of the LWFS scheduling experimentally and compared its performance with approaches including Improved Critical Path using Descendant Prediction (ICPDP), Highest Level First with Estimated Time (HLFET), Modified Critical Path (MCP) and Earliest Time First (ETF). The results of the experiments show that the proposed approach outperforms other approaches.

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Proton transport has been recognized as an essential process in many biological systems, as well as electrochemical devices including fuel cells and redox flow batteries. In the present study, we address the pressing need for solvent-free proton conducting polymer electrolytes for high-temperature PEM fuel cell applications by developing a novel all-solid polyelectrolyte membrane with a self-assembled proton-channel structure. We show that this self-assembled nanostructure endows the material with exciting ‘dry’ proton conductivity at elevated temperatures, as high as 0.3 mS cm−1 at 120 °C, making it an attractive candidate for high-temperature PEM fuel cell applications. Based on the combined investigation of solid-state NMR, FTIR and conductivity measurements, we propose that both molecular design and nano-scale structures are essential for obtaining highly conductive anhydrous proton conductors.

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Deep brain stimulation (DBS), a surgical technique to treat certain neurologic and psychiatric conditions, relies on pre-determined stimulation parameters in an open-loop configuration. The major advancement in DBS devices is a closed-loop system that uses neurophysiologic feedback to dynamically adjust stimulation frequency and amplitude. Stimulation-driven neurochemical release can be measured by fast-scan cyclic voltammetry (FSCV), but existing FSCV electrodes rely on carbon fiber, which degrades quickly during use and is therefore unsuitable for chronic neurochemical recording. To address this issue, we developed durable, synthetic boron-doped diamond-based electrodes capable of measuring neurochemical release in humans. Compared to carbon fiber electrodes, they were more than two orders-of-magnitude more physically-robust and demonstrated longevity in vitro without deterioration. Applied for the first time in humans, diamond electrode recordings from thalamic targets in patients (n = 4) undergoing DBS for tremor produced signals consistent with adenosine release at a sensitivity comparable to carbon fiber electrodes. (Clinical trials # NCT01705301).