Showing papers by "Tallinn University of Technology published in 2008"
TL;DR: In this paper, the authors used a small fraction of grown powders as absorber materials in monograin layer (MGL) solar cell structures: graphite/Cu 2 Zn 1-x Cd x Sn(Se 1-y S y ) 4 /CdS/ZnO.
Abstract: Cu 2 Zn 1-x Cd x Sn(Se 1-y S y ) 4 monograin powders with different x- and y-values were prepared from binary compounds in the liquid phase of flux material (KI) in evacuated quartz ampoules. All the materials had uniform composition and p-type conductivity. PL spectra (10 K) of the as grown Cu 2 Zn 1-x Cd x Sn(Se) 4 monograin powders showed one PL band with peak position around 0.85 eV which shifted linearly to the lower energy side with increasing Cd content. Cu 2 ZnSnS 4 material showed asymmetrical PL band at 1.31 eV attributed to band-to-tail recombination. RT Raman spectra of Cu 2 ZnSnSe 4 revealed two main peaks at 196 cm -1 and 173 cm -1 and a third less intensive peak with varying peak position in the region 231-253 cm -1 . Raman spectra of Cu 2 ZnSnS 4 showed an intensive peak at 338 cm -1 and additional peaks at 287 cm -1 and 368 cm -1 . Narrow sieved fractions of grown powders were used as absorber materials in monograin layer (MGL) solar cell structures: graphite/ Cu 2 Zn 1-x Cd x Sn(Se 1-y S y ) 4 /CdS/ZnO. The best so far solar cell that was based on the Cu 2 Zn 0.8 Cd 0.2 SnSe 4 had open circuit voltage 422 mV, short circuit current 12 mA/cm 2 and fill fac tor 44%.
337 citations
TL;DR: In this article, the authors used the landscape reconstruction algorithm (LRA) and its two models, REVEALS and LOVE, to obtain information from fossil pollen records in lakes and bogs.
Abstract: Information on the spatial distribution of past vegetation on local, regional and global scales is increasingly used within climate modelling, nature conservancy and archaeology. It is possible to obtain such information from fossil pollen records in lakes and bogs using the landscape reconstruction algorithm (LRA) and its two models, REVEALS and LOVE. These models assume that reliable pollen productivity estimates (PPEs) are available for the plant taxa involved in the quantitative reconstructions of past vegetation, and that PPEs are constant through time. This paper presents and discusses the PPEs for 15 tree and 18 herb taxa obtained in nine study areas of Europe. Observed differences in PPEs between regions may be explained by methodological issues and environmental variables, of which climate and related factors such as reproduction strategies and growth forms appear to be the most important. An evaluation of the PPEs at hand so far suggests that they can be used in modelling applications and quantitative reconstructions of past vegetation, provided that consideration of past environmental variability within the region is used to inform selection of PPEs, and bearing in mind that PPEs might have changed through time as a response to climate change. Application of a range of possible PPEs will allow a better evaluation of the results.
299 citations
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09 Oct 2008TL;DR: Ionic liquids as mentioned in this paper are a class of solvents with members possessing similar physical properties but having different chemical behavior, and their good solvating properties, together with large spectral transparency, make ionic liquids suitable for spectroscopic measurements.
Abstract: Room-temperature ionic liquids are salts with a melting point close to or below room temperature. They form liquids composed in the majority of ions. This gives these materials the potential to behave very differently when they are used as solvents compared to conventional molecular liquids. The search for their application is growing in every area of analytical chemistry—electrochemistry, chromatography, electrophoresis, and even mass spectrometry. The literature on ionic liquids is growing almost exponentially. The basis for this activity is the easy preparation of salts with different ion constituents. This ability might best be described as the “chemical tunability” of ionic liquids, a class of solvents with members possessing similar physical properties but having different chemical behavior. Their good solvating properties, together with large spectral transparency, make ionic liquids suitable solvents for spectroscopic measurements. It has been demonstrated that task-specific ionic liquids have adv...
268 citations
TL;DR: Competition of Αβ40 with ion‐selective fluorescent dyes Phen Green and Zincon showed that the KD values determined from intrinsic fluorescence ofΑβ correspond to the binding of the first Cu2+ and Zn2+ ions to the peptide with the highest affinity.
Abstract: There is evidence that binding of metal ions like Zn2+ and Cu2+ to amyloid beta-peptides (Abeta) may contribute to the pathogenesis of Alzheimer's disease. Cu2+ and Zn2+ form complexes with Abeta peptides in vitro; however, the published metal-binding affinities of Abeta vary in an enormously large range. We studied the interactions of Cu2+ and Zn2+ with monomeric Abeta(40) under different conditions using intrinsic Abeta fluorescence and metal-selective fluorescent dyes. We showed that Cu(2+) forms a stable and soluble 1 : 1 complex with Abeta(40), however, buffer compounds act as competitive copper-binding ligands and affect the apparent K(D). Buffer-independent conditional K(D) for Cu(II)-Abeta(40) complex at pH 7.4 is equal to 0.035 micromol/L. Interaction of Abeta(40) with Zn2+ is more complicated as partial aggregation of the peptide occurs during zinc titration experiment and in the same time period (within 30 min) the initial Zn-Abeta(40) complex (K(D) = 60 micromol/L) undergoes a transition to a more tight complex with K(D) approximately 2 micromol/L. Competition of Abeta(40) with ion-selective fluorescent dyes Phen Green and Zincon showed that the K(D) values determined from intrinsic fluorescence of Abeta correspond to the binding of the first Cu2+ and Zn2+ ions to the peptide with the highest affinity. Interaction of both Zn2+ and Cu2+ ions with Abeta peptides may occur in brain areas affected by Alzheimer's disease and Zn2+-induced transition in the peptide structure might contribute to amyloid plaque formation.
208 citations
TL;DR: The widespread expression of MANF together with its evolutionary conserved nature and regulation by brain insults suggest that it has important functions both under normal and pathological conditions in many tissue types.
174 citations
TL;DR: Considering an excellent correlation between both formats, 96-well microplate Flash Assay can be successfully used for high throughput evaluation of harmful properties of chemicals (including organic and inorganic NPs) to bacteria.
165 citations
TL;DR: In this article, a simulation approach developed by Sugita (the computer model POLLSCAPE) which uses models based on the theory of pollen analysis is presented together with examples of application, each of which explores a possible use of the POLLANDCAL tools and a means of validating or evaluating the models with empirical data.
Abstract: Information on past land cover in terms of absolute areas of different landscape units (forest, open land, pasture land, cultivated land, etc.) at local to regional scales is needed to test hypotheses and answer questions related to climate change (e.g. feedbacks effects of land-cover change), archaeological research, and nature conservancy (e.g. management strategy). The palaeoecological technique best suited to achieve quantitative reconstruction of past vegetation is pollen analysis. A simulation approach developed by Sugita (the computer model POLLSCAPE) which uses models based on the theory of pollen analysis is presented together with examples of application. POLLSCAPE has been adopted as the central tool for POLLANDCAL (POLlen/LANdscape CALibration), an international research network focusing on this topic. The theory behind models of the pollen–vegetation relationship and POLLSCAPE is reviewed. The two model outputs which receive greatest attention in this paper are the relevant source area of pollen (RSAP) and pollen loading in mires and lakes. Six examples of application of POLLSCAPE are presented, each of which explores a possible use of the POLLANDCAL tools and a means of validating or evaluating the models with empirical data. The landscape and vegetation factors influencing the size of the RSAP, the importance of pollen productivity estimates (PPEs) for the model outputs, the detection of small and rare patches of plant taxa in pollen records, and quantitative reconstructions of past vegetation and landscapes are discussed on the basis of these examples. The simulation approach is seen to be useful both for exploring different vegetation/landscape scenarios and for refuting hypotheses.
164 citations
TL;DR: In this article, an extremely thin absorber (ETA) layer solar cell was realized by the chemical spray pyrolysis method, where a CuInS2 absorber was deposited onto a blocking layer coated ZnO nanorods grown on a transparent conductive oxide.
152 citations
TL;DR: In this article, the essential oil composition of Pimpinella anisum L. fruits obtained from different geographical areas of Europe were determined using capillary GC and GC-MS techniques.
128 citations
TL;DR: A CT scan study of an undisturbed pectoral fin of Panderichthys is presented demonstrating that the plate-like ‘ulnare’ of previous reconstructions is an artefact and that distal radials are in fact present and makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal Radials present in all sarcopterygian fish.
Abstract: One of the identifying characteristics of tetrapods (limbed vertebrates) is the presence of fingers and toes. Whereas the proximal part of the tetrapod limb skeleton can easily be homologized with the paired fin skeletons of sarcopterygian (lobe-finned) fish, there has been much debate about the origin of digits. Early hypotheses interpreted digits as derivatives of fin radials, but during the 1990s the idea gained acceptance that digits are evolutionary novelties without direct equivalents in fish fin skeletons. This was partly based on developmental genetic data, but also substantially on the pectoral fin skeleton of the elpistostegid (transitional fish/tetrapod) Panderichthys, which appeared to lack distal digit-like radials. Here we present a CT scan study of an undisturbed pectoral fin of Panderichthys demonstrating that the plate-like 'ulnare' of previous reconstructions is an artefact and that distal radials are in fact present. This distal portion is more tetrapod-like than that found in Tiktaalik and, in combination with new data about fin development in basal actinopterygians, sharks and lungfish, makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal radials present in all sarcopterygian fish.
121 citations
TL;DR: In this paper, the authors used electrochemical quartz crystal microbalance (EQCM) to determine the optimal electrosynthesis parameters for the formation of a smooth and uniform PPy/ l -Asp films, the overoxidized polypyrrole (oPPy) matrix templated with either l - or d -aspartic acid ( l -, d - Asp) was evaluated as a potential enantioselective recognition element.
TL;DR: Redox properties of the disulfides of human Cox17, here investigated, strongly support the current hypothesis that the unstructured fully reduced Cox17 protein is present in the cytoplasm and enters the intermembrane space (IMS) where is then oxidized by Mia40 to Cox172S-S, thus becoming partially structured and trapped into the IMS.
TL;DR: In this article, a dual internal variable is introduced to provide the corresponding evolution equations depending on whether the Onsager-Casimir reciprocity relations are satisfied or not, and the unification is achieved by means of the introduction of a dual Internal Variable.
Abstract: Dynamic degrees of freedom and internal variables are treatedin a uniform way. The unification is achieved by means of the introduction of a dual internal variable. This duality provides the corresponding evolution equations depending on whether the Onsager–Casimir reciprocity relations are satisfied or not.
TL;DR: In this article, a review of international and national practices in investment decision support tools in bridges and road quality management is presented, where the authors suggest that more than one approach should be regarded as complementary instead of competitive means.
Abstract: Multi-attribute analysis (MAA) is a popular tool in many economical, managerial, and constructional problems. This document provides a review of international and national practices in investment decision support tools in bridges and road quality management. Cost benefit analysis (CBA) and MAA are principal methodologies in supporting decisionmaking in bridges and road quality management. The complexity of the applications shows significant differences in international practices. There are ongoing discussions among practitioners and researchers, regarding which one is more appropriate in supporting decisionmaking. It is suggested that more than one approach should be regarded as complementary instead of competitive means. MAA may be particularly helpful in early stages of project development and strategic planning. CBA is used most widely for project prioritization and selecting the final project from a set of alternatives. These methodologies are applicable to the problems with large numbers of scenarios and attributes. The research has concluded that multi-attribute decisionmaking methods are very useful for bridge and road construction.
TL;DR: In this paper, wave conditions in the northern Baltic proper during windstorm Erwin/Gudrun (January 2005) are analyzed based on in situ measurements in three locations and output of operational wave models from the German Weather Forecast Service, the Danish Meteorological Institute and the Finnish Institute of Marine Research.
Abstract: . Wave conditions in the northern Baltic Proper during windstorm Erwin/Gudrun (January 2005) are analysed based on in situ measurements in three locations and output of operational wave models from the German Weather Forecast Service, the Danish Meteorological Institute and the Finnish Institute of Marine Research. The measured significant wave height reached 7.2 m in the northern Baltic Proper and 4.5 m in the Gulf of Finland. The roughest wave conditions, estimated from the comparison of the forecast and measured data, occurred remote from the sensors, off the coasts of Saaremaa and Latvia where the significant wave height was about 9.5 m. Peak periods exceeded 12 s in a large part of the northern Baltic Proper and in the central part of the Gulf of Finland.
TL;DR: It is argued that symmetric (semi)monoidal comonads provide a means to structure context-dependent notions of computation such as notions of dataflow computation (computation on streams) and of tree relabelling as in attribute evaluation.
TL;DR: Complete kinetic analysis of uMtCK reaction in isolated brain mitochondria showed that oxidative phosphorylation specifically altered only the dissociation constants for MgATP, by decreasing that from ternary complex MtCK.
Abstract: The role of ubiquitous mitochondrial creatine kinase (uMtCK) reaction in regulation of mitochondrial res- piration was studied in purified preparations of rat brain synaptosomes and mitochondria. In permeabilized synapto- somes, apparent Km for exogenous ADP, Km (ADP), in regulation of respiration in situ was rather high (110 ± 11lM) in comparison with isolated brain mitochondria (9 ± 1 lM). This apparent Km for ADP observed in isolated mitochondria in vitro dramatically increased to 169 ± 52lM after their incubation with 1 lM of dimeric tubulin showing that in rat brain, particularly in synaptosomes, mitochondrial outer membrane permeability for ADP, and ATP may be restricted by tubulin binding to voltage depen- dent anion channel (VDAC). On the other hand, in synaptosomes apparent Km (ADP) decreased to 25 ± 1 lM in the presence of 20 mM creatine. To fully understand this effect of creatine on kinetics of respiration regulation, com- plete kinetic analysis of uMtCK reaction in isolated brain mitochondria was carried out. This showed that oxidative phosphorylation specifically altered only the dissociation constants for MgATP, by decreasing that from ternary com- plex MtCK.Cr.MgATP (Ka )f rom 0.13± 0.02 to 0.018 ± 0.007 mM and that from binary complex MtCK.MgATP (Kia) from 1.1 ± 0.29 mM to 0.17 ± 0.07 mM. Apparent decrease of dissociation constants for MgATP reflects effec- tive cycling of ATP and ADP between uMtCK and adenine nucleotide translocase (ANT). These results emphasize important role and various pathophysiological implications of the phosphocreatine-creatine kinase system in energy transfer in brain cells, including synaptosomes.
TL;DR: The application of Fenton-like oxidation with subsequent iron (III)/lime coagulation did not only enhance the quality of pharmaceutical effluents with different chemical characteristics and help to meet the requirements for wastewater discharged to sewage, but also improve the biodegradability of pharmaceuticaleffluents.
TL;DR: The results corroborate the predictions of the EEH, implying that the endotherm community and the vegetation of the North European tundra behaves dynamically as if each trophic level consisted of a single population, in spite of local co‐occurrence of >20 plant species representing different major taxonomic groups, growth forms, and defensive strategies.
Abstract: According to the exploitation ecosystems hypothesis (EEH), productive terrestrial ecosystems are characterized by community‐level trophic cascades, whereas unproductive ecosystems harbor food‐limited grazers, which regulate community‐level plant biomass. We tested this hypothesis along arctic‐alpine productivity gradients at the Joatka field base, Finnmark, Norway. In unproductive habitats, mammalian predators were absent and plant biomass was constant, whereas herbivore biomass varied, reflecting the productivity of the habitat. In productive habitats, predatory mammals were persistently present and plant biomass varied in space, but herbivore biomass did not. Plant biomass of productive tundra scrublands declined by 40% when vegetation blocks were transferred to predation‐free islands. Corresponding transfer to herbivore‐free islands triggered an increase in plant biomass. Fertilization of an unproductive tundra heath resulted in a fourfold increase in rodent density and a corresponding increa...
TL;DR: In this article, the performance of PV modules with daily two-positional tracking is analyzed, corresponding to the positions of the sun in the morning and in the afternoon, and the results indicate that the seasonal energy yield is increased by 10-20% over the yield from a fixed south-facing collector tilted at an optimal angle.
TL;DR: A practical method for determining diffusion coefficients in anisotropic medium and to estimate the overall diffusion coefficients of fluorescently labeled ATP in rat cardiomyocytes are developed using extended raster image correlation spectroscopy protocols to be able to discriminate the anisotropy in the diffusion coefficient tensor.
Abstract: A series of experimental data points to the existence of profound diffusion restrictions of ADP/ATP in rat cardiomyocytes. This assumption is required to explain the measurements of kinetics of res...
TL;DR: In this article, the degradation of salicylic acid (SA) was carried out utilizing classical Fenton reagents and modified Fenton with ferric iron salt and goethite as source of iron catalyst.
TL;DR: A set of soil microbiological and biochemical properties was used to assess the influence of agricultural practices such as rotation, usage of pesticides, and fertilizers on the three most widespread soil types (Calcaric Regosols, Calcaric Cambisols and Stagnic Luvisols) in the fields of horticultural farms throughout Estonia as mentioned in this paper.
TL;DR: The practical utilization of a new type of surfactant in MEKC was evaluated by introducing an ionic liquid into the running aqueous buffer to separate neutral analytes-methylresorcinol isomers and benzene derivatives.
TL;DR: The findings suggest that the effect of the 450 MHz microwave radiation modulated at 7, 14 and 21 Hz varies depending on the modulation frequency, while differences were found in individual sensitivity to exposure.
Abstract: Purpose: The aim of this study was to evaluate the effect of microwaves modulated at different frequencies on human electroencephalographic (EEG) rhythms.Materials and methods: Thirteen healthy volunteers were exposed to microwaves (450 MHz) pulse-modulated at frequencies of 7, 14 and 21 Hz. The field power density at the scalp was 0.16 mW/cm2. Our experimental protocol consisted of two five-cycle (1 min on and 1 min off) series of exposures at fixed modulation frequencies. A relative change in the EEG power with and without exposure was used as a quantitative measure. EEG frequencies recorded in the theta (4 – 6.8 Hz), alpha (8 – 13 Hz), beta1 (15 – 20 Hz), and beta2 (22 – 38 Hz) bands were analyzed.Results: Modulated microwaves caused an increase in the average EEG alpha (17%) and beta (7%) power but the theta rhythm remained unaffected. Increases in the EEG alpha and beta power were statistically significant during the first half-period of the exposure interval (30 s) at the modulation frequencies of 1...
TL;DR: The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas as discussed by the authors, and is inferred here to have been a part of the Timanide margin of Baltica at least since the Vendian.
Abstract: The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by decollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the decollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with those in the upper structural level along the major N-trending Fiordovoe Lake Fault Zone, which involved several kilometres of dextral strike-slip movement and downthrow to the west. A major Early Carboniferous unconformity separates the folded Mid-Palaeozoic and older rocks from overlying Carboniferous formations, as on Franz Joseph Land and Svalbard. Subsequent latest Palaeozoic to Early Mesozoic orogeny, as on Taimyr, apparently had little influence on the Severnaya Zemlya successions.
TL;DR: The multires onancelike behavior of the variance and the signal-to-noise ratio as functions of the noise correlation time are observed and the connection between the occurrence of energetic instability and the phenomenon of stochastic multiresonance is established.
Abstract: The long-time behavior of the first two moments and the correlation function for the output signal of a harmonic oscillator with fluctuating frequency subjected to an external periodic force and an additive thermal noise is considered analytically. The colored fluctuations of the oscillator frequency are modeled as a three-level Markovian noise. Using the Shapiro-Loginov formula, the exact expressions of several stochastic resonance (SR) characteristics such as the spectral amplification, the variance of the output signal, the signal-to-noise ratio, and the SR gain have been calculated. The nonmonotonic dependence of the SR characteristics versus the noise parameters as well as versus the input signal frequency and also the conditions for the appearance of energetic instability are analyzed. In particular, the multiresonancelike behavior of the variance and the signal-to-noise ratio as functions of the noise correlation time are observed and the connection between the occurrence of energetic instability and the phenomenon of stochastic multiresonance is established. Some unexpected effects such as the hypersensitive response of the spectral amplification to small variations of the noise amplitude encountered in the case of a large flatness of the colored noise are also discussed.
TL;DR: The results show that alternatively spliced NFAT mRNAs are expressed differentially and could contribute to the diversity of functions of the NFAT proteins.
09 Nov 2008
TL;DR: This paper introduces a set of computation rules to determine the attacker's exact expected outcome based on a multi-parameter attack tree and compares them to a previously proposed computational semantics by Buldas et al. and proves that the new semantics always provides at least the same outcome.
Abstract: In this paper we introduce a set of computation rules to determine the attacker's exact expected outcome based on a multi-parameter attack tree. We compare these rules to a previously proposed computational semantics by Buldas et al . and prove that our new semantics always provides at least the same outcome. A serious drawback of our proposed computations is the exponential complexity. Hence, implementation becomes an important issue. We propose several possible optimisations and evaluate the result experimentally. Finally, we also prove the consistency of our computations in the framework of Mauw and Oostdijk and discuss the need to extend the framework.
TL;DR: Different waveforms for excitation are considered and not only the advantages but also their limitations are discussed and the chirp excitation has been found to be most promising in terms of frequency range, signal-to-noise ratio and crest factor.
Abstract: Frequency domain impedance measurements are still the common approach in assessing passive electrical properties of cells and tissues. However, due to the time requirements for sweeping over a frequency range for performing spectroscopy, they are not suited for recovering fast impedance changes of biological objects. The use of broad bandwidth excitation and monitoring the response as a function of time will greatly reduce the measurement time. The widespread usage of a square wave excitation is simple but not always the best choice. Here we consider different waveforms for excitation and discuss not only the advantages but also their limitations. Measurements in a miniaturized chamber where frequency and time domain measurements are compared show the suitability of different waveforms as excitation signals for the measurements of bio-impedance. The chirp excitation has been found to be most promising in terms of frequency range, signal-to-noise ratio and crest factor.