Showing papers by "Tallinn University of Technology published in 2015"

Grid-Connected Photovoltaic Systems: An Overview of Recent Research and Emerging PV Converter Technology

Abstract: Photovoltaic (PV) energy has grown at an average annual rate of 60% in the last five years, surpassing one third of the cumulative wind energy installed capacity, and is quickly becoming an important part of the energy mix in some regions and power systems. This has been driven by a reduction in the cost of PV modules. This growth has also triggered the evolution of classic PV power converters from conventional single-phase grid-tied inverters to more complex topologies to increase efficiency, power extraction from the modules, and reliability without impacting the cost. This article presents an overview of the existing PV energy conversion systems, addressing the system configuration of different PV plants and the PV converter topologies that have found practical applications for grid-connected systems. In addition, the recent research and emerging PV converter technology are discussed, highlighting their possible advantages compared with the present technology.

Biodegradation of ionic liquids – a critical review

Abstract: The importance of biodegradation data as part of the design of safer chemicals is presented using ionic liquids (ILs) as a model study. Structural features that promote/impede IL biodegradation, IL design strategies, methods of biodegradation analysis, properties of IL/surfactant derivatives and computational methods of predicting biodegradation are discussed. The importance of metabolite studies as part of biodegradation assays is highlighted. The relevance of applying the lessons learned developing biodegradable ILs to other chemical classes is proposed. A comprehensive appendix of IL biodegradation data published since 2010 (∼300 ILs) has been compiled.

A Review on the Green Synthesis of Silver Nanoparticles and Their Morphologies Studied via TEM

Abstract: Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology.

Twenty-five-year trends in myocardial infarction attack and mortality rates, and case-fatality, in six European populations

Abstract: Objective Due to the burden of coronary heart disease (CHD), the monitoring of CHD trends is required. This study sought to examine the acute myocardial infarction (AMI) trends in attack and mortality rates, and in 28-day case-fatality, in six European populations during 1985–2010. Methods Data consisted of 78 128 AMI events included in eight population-based registries from Finland (several populations), Italy (Brianza and Varese), Germany (Augsburg), France (Haute-Garonne), Spain (Girona) and Estonia (Tallinn). AMI event rates and case-fatality trends were analysed using the annual percentage change (APC) obtained by negative binomial and joinpoint regression. Results AMI attack and mortality rates decreased in most populations. Finland experienced the steepest decline in attack rates (APC=−4.4% (95% CI −5.1 to −2.9) in men; −4.0% (−5.1 to −2.8), in women). Total-hospital and inhospital case-fatality decreased in all populations except in Tallinn. The steepest decline in total case-fatality occurred in Spain (−3.8% (−5.3 to −2.4) in men; −5.1% (−6.9 to −3.3) in women). Prehospital case-fatality trends differed significantly by population and sex. The trends for all included populations showed a significant decline in AMI event rates and case-fatality, in both sexes and all age groups. However, in women aged 65–74 years, a significant increase in total case-fatality occurred in 2005–2010 (4.7% (0.7 to 8.8)). Conclusions AMI event rates and inhospital case-fatality declined in 1985–2010 in almost all populations analysed. Prehospital case-fatality declined only in certain population groups, showing differences by sex. These results highlight the need of specific strategies in AMI prevention for certain groups and populations.

The Benefits of Self-Awareness and Attention in Fog and Mist Computing

Abstract: Self-awareness facilitates a proper assessment of cost-constrained cyber-physical systems, allocating limited resources where they are most needed. Together, situation awareness and attention are key enablers for self-awareness in efficient distributed sensing and computing networks.

Disordered Lithium-Rich Oxyfluoride as a Stable Host for Enhanced Li+ Intercalation Storage

Abstract: Dr. R. Chen, Dr. M. Knapp, Prof. M. Fichtner, Prof. H. Hahn Helmholtz Institute Ulm, 89081 Ulm, Germany E-mail: ruiyong.chen@kit.edu Dr. R. Chen, Dr. S. Ren, Dr. D. Wang, Dr. R. Witter, Prof. M. Fichtner, Prof. H. Hahn Institute of Nanotechnology, Karlsruhe Institute of Technology P.O. Box 3640, 76021 Karlsruhe, Germany Dr. M. Knapp Institute for Applied Materials, Karlsruhe Institute of Technology P.O. Box 3640, 76021 Karlsruhe, Germany Dr. R. Witter Technomedicum, Tallinn University of Technology 19086 Tallinn, Estonia Prof. H. Hahn Joint Research Laboratory Nanomaterials, Technische Universität Darmstadt 64287 Darmstadt, Germany

LogCluster — A data clustering and pattern mining algorithm for event logs

Abstract: Modern IT systems often produce large volumes of event logs, and event pattern discovery is an important log management task. For this purpose, data mining methods have been suggested in many previous works. In this paper, we present the LogCluster algorithm which implements data clustering and line pattern mining for textual event logs. The paper also describes an open source implementation of LogCluster.

The CB 1 cannabinoid receptor signals striatal neuroprotection via a PI3K/Akt/mTORC1/BDNF pathway

Abstract: The CB1 cannabinoid receptor, the main molecular target of endocannabinoids and cannabis active components, is the most abundant G protein-coupled receptor in the mammalian brain. In particular, the CB1 receptor is highly expressed in the basal ganglia, mostly on terminals of medium-sized spiny neurons, where it plays a key neuromodulatory function. The CB1 receptor also confers neuroprotection in various experimental models of striatal damage. However, the assessment of the physiological relevance and therapeutic potential of the CB1 receptor in basal ganglia-related diseases is hampered, at least in part, by the lack of knowledge of the precise mechanism of CB1 receptor neuroprotective activity. Here, by using an array of pharmacological, genetic and pharmacogenetic (designer receptor exclusively activated by designer drug) approaches, we show that (1) CB1 receptor engagement protects striatal cells from excitotoxic death via the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin complex 1 pathway, which, in turn, (2) induces brain-derived neurotrophic factor (BDNF) expression through the selective activation of BDNF gene promoter IV, an effect that is mediated by multiple transcription factors. To assess the possible functional impact of the CB1/BDNF axis in a neurodegenerative-disease context in vivo, we conducted experiments in the R6/2 mouse, a well-established model of Huntington's disease, in which the CB1 receptor and BDNF are known to be severely downregulated in the dorsolateral striatum. Adeno-associated viral vector-enforced re-expression of the CB1 receptor in the dorsolateral striatum of R6/2 mice allowed the re-expression of BDNF and the concerted rescue of the neuropathological deficits in these animals. Collectively, these findings unravel a molecular link between CB1 receptor activation and BDNF expression, and support the relevance of the CB1/BDNF axis in promoting striatal neuron survival.

Twenty-five-year trends in myocardial infarction attack and mortality rates, and case-fatality, in six European populations

Abstract: Objective Due to the burden of coronary heart disease (CHD), the monitoring of CHD trends is required. This study sought to examine the acute myocardial infarction (AMI) trends in attack and mortality rates, and in 28-day case-fatality, in six European populations during 1985–2010. Methods Data consisted of 78 128 AMI events included in eight population-based registries from Finland (several populations), Italy (Brianza and Varese), Germany (Augsburg), France (Haute-Garonne), Spain (Girona) and Estonia (Tallinn). AMI event rates and case-fatality trends were analysed using the annual percentage change (APC) obtained by negative binomial and joinpoint regression. Results AMI attack and mortality rates decreased in most populations. Finland experienced the steepest decline in attack rates (APC=−4.4% (95% CI −5.1 to −2.9) in men; −4.0% (−5.1 to −2.8), in women). Total-hospital and inhospital case-fatality decreased in all populations except in Tallinn. The steepest decline in total case-fatality occurred in Spain (−3.8% (−5.3 to −2.4) in men; −5.1% (−6.9 to −3.3) in women). Prehospital case-fatality trends differed significantly by population and sex. The trends for all included populations showed a significant decline in AMI event rates and case-fatality, in both sexes and all age groups. However, in women aged 65–74 years, a significant increase in total case-fatality occurred in 2005–2010 (4.7% (0.7 to 8.8)). Conclusions AMI event rates and inhospital case-fatality declined in 1985–2010 in almost all populations analysed. Prehospital case-fatality declined only in certain population groups, showing differences by sex. These results highlight the need of specific strategies in AMI prevention for certain groups and populations.

Proteome reallocation in Escherichia coli with increasing specific growth rate

Abstract: Cells usually respond to changing growth conditions with a change in the specific growth rate (μ) and adjustment of their proteome to adapt and maintain metabolic efficiency. Description of the principles behind proteome resource allocation is important for understanding metabolic regulation in response to changing μ. Thus, we analysed the proteome resource allocation dynamics of Escherichia coli into different metabolic processes in response to changing μ. E. coli was grown on minimal and defined rich media in steady state continuous cultures at different μ and characterised combining two LC-MS/MS-based proteomics methods: stable isotope labelling by amino acids in cell culture (SILAC) and intensity based label-free absolute quantification. We detected slowly growing cells investing more proteome resources in energy generation and carbohydrate transport and metabolism whereas for achieving faster growth cells needed to devote most resources to translation and processes closely related to the protein synthesis pipeline. Furthermore, down-regulation of energy generation and carbohydrate metabolism proteins with faster growth displayed very similar expression dynamics with the global transcriptional regulator CRP (cyclic AMP receptor protein), pointing to a dominant protein resource allocating role of this protein. Our data also suggest that acetate overflow may be the result of global proteome resource optimisation as cells saved proteome resources by switching from fully respiratory to respiro-fermentative growth. The presented results give a quantitative overview of how E. coli adjusts its proteome to achieve faster growth and in future could contribute to the design of more efficient cell factories through proteome optimisation.

LSTM for punctuation restoration in speech transcripts.

Abstract: The output of automatic speech recognition systems is generally an unpunctuated stream of words which is hard to process for both humans and machines. We present a two-stage recurrent neural network based model using long short-term memory units to restore punctuation in speech transcripts. In the first stage, textual features are learned on a large text corpus. The second stage combines textual features with pause durations and adapts the model to speech domain. Our approach reduces the number of punctuation errors by up to 16.9% when compared to a decision tree that combines hidden-event language model posteriors with inter-word pause information, having largest improvements in period restoration.

Copulation in antiarch placoderms and the origin of gnathostome internal fertilization

Abstract: The discovery of claspers in fossils of antiarch placoderms, an ancient group of armoured fish, suggests that internal fertilization was the ancestral type of reproduction for all jawed vertebrates: this contrasts with the current understanding that external fertilization must be the ancestral state. It is usually assumed that internal fertilization by copulation, where it occurs, must have evolved from external fertilization such as free spawning. Many sharks, however, have internal fertilization facilitated by pelvic organs in the males known as claspers. Claspers have also been described in two groups of placoderms, the arthrodires and ptyctodonts, ancient jawed vertebrates known only as fossils, suggesting that internal fertilization in jawed vertebrates may have been the primitive state. Arthrodires and ptyctodonts are derived placoderms however, leaving open the possibility that they evolved claspers independently. This now seems unlikely following the description of claspers in a third and extremely primitive placoderm group, the antiarchs. This creates a new puzzle. Placoderms are often viewed as 'stem' gnathostomes from which all modern jawed vertebrates evolved. So either internal fertilization was primitive for all jawed vertebrates, or placoderms were an evolutionary dead-end in which claspers evolved several times independently. Reproduction in jawed vertebrates (gnathostomes) involves either external or internal fertilization1. It is commonly argued that internal fertilization can evolve from external, but not the reverse. Male copulatory claspers are present in certain placoderms2,3,4, fossil jawed vertebrates retrieved as a paraphyletic segment of the gnathostome stem group in recent studies5,6,7,8. This suggests that internal fertilization could be primitive for gnathostomes, but such a conclusion depends on demonstrating that copulation was not just a specialized feature of certain placoderm subgroups. The reproductive biology of antiarchs, consistently identified as the least crownward placoderms5,6,7,8 and thus of great interest in this context, has until now remained unknown. Here we show that certain antiarchs possessed dermal claspers in the males, while females bore paired dermal plates inferred to have facilitated copulation. These structures are not associated with pelvic fins. The clasper morphology resembles that of ptyctodonts, a more crownward placoderm group7,8, suggesting that all placoderm claspers are homologous and that internal fertilization characterized all placoderms. This implies that external fertilization and spawning, which characterize most extant aquatic gnathostomes, must be derived from internal fertilization, even though this transformation has been thought implausible. Alternatively, the substantial morphological evidence for placoderm paraphyly must be rejected.

Creation of Smart-Contracting Collaborations for Decentralized Autonomous Organizations

Abstract: Electronic communities of decentralized autonomous organizations (DAO) that engage in agile business-network collaborations, are enabled by recent blockchain-technology related innovations using smart contracting. DAOs utilize service-oriented cloud computing in a loosely-coupled collaboration lifecycle that commences with the setup phase. The latter supports the selection of services provided and used by DAOs in combination with smart contract negotiations. Such setup phases for DAO-communities use blueprints of business-network models that DAOs populate with tentative service offers. The negotiation phase may result either in a consensual agreement, a counteroffer, or a disagreement. In the latter case, the smart contract negotiation collapses and the lifecycle returns to the beginning of the selected collaboration blueprints. To the best of our knowledge, such a smart-contracting setup lifecycle has not been formalized so far. The paper fills the gap and evaluates the model with means of model-checking methods.

Protein resonance assignment at MAS frequencies approaching 100 kHz: a quantitative comparison of J-coupling and dipolar-coupling-based transfer methods

Abstract: We discuss the optimum experimental conditions to obtain assignment spectra for solid proteins at magic-angle spinning (MAS) frequencies around 100 kHz We present a systematic examination of the MAS dependence of the amide proton T 2′ times and a site-specific comparison of T 2′ at 93 kHz versus 60 kHz MAS frequency A quantitative analysis of transfer efficiencies of building blocks, as they are used for typical 3D experiments, was performed To do this, we compared dipolar-coupling and J-coupling based transfer steps The building blocks were then combined into 3D experiments for sequential resonance assignment, where we evaluated signal-to-noise ratio and information content of the different 3D spectra in order to identify the best assignment strategy Based on this comparison, six experiments were selected to optimally assign the model protein ubiquitin, solely using spectra acquired at 93 kHz MAS Within 3 days of instrument time, the required spectra were recorded from which the backbone resonances have been assigned to over 96 %

Plant macrofossil evidence for an early onset of the Holocene summer thermal maximum in northernmost Europe

Abstract: Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago. However, pollen-based temperature reconstructions are largely driven by changes in the proportions of tree taxa, and thus the early-Holocene warming signal may be delayed due to the geographical disequilibrium between climate and tree populations. Here we show that quantitative summer-temperature estimates in northern Europe based on macrofossils of aquatic plants are in many cases ca. 2 °C warmer in the early Holocene (11,700-7,500 years ago) than reconstructions based on pollen data. When the lag in potential tree establishment becomes imperceptible in the mid-Holocene (7,500 years ago), the reconstructed temperatures converge at all study sites. We demonstrate that aquatic plant macrofossil records can provide additional and informative insights into early-Holocene temperature evolution in northernmost Europe and suggest further validation of early post-glacial climate development based on multi-proxy data syntheses.

On the accuracy of the Haar wavelet discretization method

Abstract: Current study contains adaption of Haar wavelet discretization method (HWDM) for FG beams and its accuracy estimates. The convergence analysis is performed for differential equations covering a wide class of composite and nanostructures. Corresponding error bound has been derived. It has been shown that the order of convergence of the HWDM can be increased from two to four by applying Richardson extrapolation method. The theoretical estimates are validated by numerical samples considering FGM beam as a model problem. The results obtained by applying HWDM are compared with the results of finite difference method (FDM).

Assessing the CNH-CNY Pricing Differential: Role of Fundamentals, Contagion and Policy

Abstract: Renminbi internationalisation has brought about an active offshore market where the exchange rate frequently diverges from the onshore market Using extended GARCH models, we explore the role of fundamentals, global factors and policies related to renminbi internationalisation in driving the pricing differential between the onshore and offshore exchange rates Differences in the liquidity of the two markets play an important role in explaining the level of the differential, while rises in global risk aversion tend to increase the differential's volatility On the policy front, measures permitting cross-border renminbi outflows have a particularly discernible impact in reducing the volatility of the pricing gap between the two markets