Showing papers by "Bulgarian Academy of Sciences published in 2004"
TL;DR: A real-time detection method for QRS and ventricular beat detection based on comparison between absolute values of summed differentiated electrocardiograms of one of more ECG leads and adaptive threshold, which is higher than, or comparable to, those cited in the scientific literature.
Abstract: QRS and ventricular beat detection is a basic procedure for electrocardiogram (ECG) processing and analysis. Large variety of methods have been proposed and used, featuring high percentages of correct detection. Nevertheless, the problem remains open especially with respect to higher detection accuracy in noisy ECGs A real-time detection method is proposed, based on comparison between absolute values of summed differentiated electrocardiograms of one of more ECG leads and adaptive threshold. The threshold combines three parameters: an adaptive slew-rate value, a second value which rises when high-frequency noise occurs, and a third one intended to avoid missing of low amplitude beats. Two algorithms were developed: Algorithm 1 detects at the current beat and Algorithm 2 has an RR interval analysis component in addition. The algorithms are self-adjusting to the thresholds and weighting constants, regardless of resolution and sampling frequency used. They operate with any number L of ECG leads, self-synchronize to QRS or beat slopes and adapt to beat-to-beat intervals. The algorithms were tested by an independent expert, thus excluding possible author's influence, using all 48 full-length ECG records of the MIT-BIH arrhythmia database. The results were: sensitivity Se = 99.69 % and specificity Sp = 99.65 % for Algorithm 1 and Se = 99.74 % and Sp = 99.65 % for Algorithm 2. The statistical indices are higher than, or comparable to those, cited in the scientific literature.
426 citations
TL;DR: Oblzor et al. as discussed by the authors found that heavy metal accumulation in barley leaves leads to different display of oxidative stress, and changes in individual chloroplast proteins, including Rubisco subunits, and showed that low-molecular antioxidants were most probably the consequence of depletion in low-protein antioxidants as a result of their involvement in detoxification processes and disbalance in antioxidative enzymes.
379 citations
14 Jun 2004
TL;DR: This paper analyzes the building blocks of smart houses, with particular attention paid to the health monitoring subsystem as an important component, by addressing the basic requirements of various sensors implemented from both research and clinical perspectives.
Abstract: Smart houses are considered a good alternative for the independent life of older persons and persons with disabilities. Numerous intelligent devices, embedded into the home environment, can provide the resident with both movement assistance and 24-h health monitoring. Modern home-installed systems tend to be not only physically versatile in functionality but also emotionally human-friendly, i.e., they may be able to perform their functions without disturbing the user and without causing him/her any pain, inconvenience, or movement restriction, instead possibly providing him/her with comfort and pleasure. Through an extensive survey, this paper analyzes the building blocks of smart houses, with particular attention paid to the health monitoring subsystem as an important component, by addressing the basic requirements of various sensors implemented from both research and clinical perspectives. The paper will then discuss some important issues of the future development of an intelligent residential space with a human-friendly health monitoring functional system.
360 citations
TL;DR: Ablation of Fe by ultrashort laser pulses with durations 0.1, 1, and 5 ps were investigated experimentally in this paper, showing that the change in the ablation rate is connected to an overheating of the material above the critical point, which results in a steep rise of the pressure developed.
Abstract: Ablation of Fe by ultrashort laser pulses with durations 0.1, 1, and 5 ps were investigated experimentally. The laser fluence varied from the ablation threshold up to 100 J cm−2. Above 1 J cm−2, the ablation rate depended on the laser pulse duration, with the shortest pulse producing the highest value. A change in the ablation rate as the laser fluence increased was also observed. These results were analysed using molecular dynamics simulations. We show that the change in the ablation rate is connected to an overheating of the material above the critical point, which results in a steep rise of the pressure developed. Furthermore, due to the electron heat diffusion, the overheated volume increases and involves material located deeper than the skin depth. An increase in the pulse duration results in a decrease in the degree of overheating.
340 citations
TL;DR: The validation of rapid, low-cost spectrophotometric procedures for the quantification of the three main groups of bioactive substances in poplar-type propolis has been performed and two sets of results agreed satisfactory, as proven by Student's t-test.
Abstract: The validation of rapid, low-cost spectrophotometric procedures for the quantification of the three main groups of bioactive substances (flavones and flavonols, flavanones and dihydroflavonols, and total phenolics) in poplar-type propolis has been performed. A spectrophotometric assay based on the formation of an aluminium chloride complex was applied for the quantification of total flavones and flavonols using galangin as standard. Because of the high amount of flavanones and dihydroflavonols in “poplar type” propolis, the introduction of a distinct procedure for their quantification was considered of special significance and the DAB9 colorimetric method was applied for the purpose. Total phenolic content was measured by the Folin–Ciocalteu procedure using a mixture of pinocembrin and galangin as a reference. The procedures were validated using a model mixture of compounds representing the poplar-type propolis composition as found in previous studies. The accuracy (recovery) varied in the range 84–109%, and the relative standard deviation was 0.5–6.2%. The developed spectrophotometric procedures were applied to six poplar type propolis samples. The results were verified independently by a HPLC procedure. The two sets of results agreed satisfactory, as proven by Student's t-test. Copyright © 2004 John Wiley & Sons, Ltd.
306 citations
01 Jan 2004
TL;DR: A variant of the generic ensemble method where the number of overproduced clusters is chosen randomly for every ensemble member (partition) is proposed and it is shown that this approach increases the spread of the diversity within the ensemble thereby leading to a better match with the known cluster labels.
Abstract: The pairwise approach to cluster ensembles uses multiple partitions, each of which constructs a coincidence matrix between all pairs of objects. The matrices for the partitions are then combined and a final clustering is derived thereof. Here we study the diversity within such cluster ensembles. Based on this, we propose a variant of the generic ensemble method where the number of overproduced clusters is chosen randomly for every ensemble member (partition). Using three artificial sets we show that this approach increases the spread of the diversity within the ensemble thereby leading to a better match with the known cluster labels. Experimental results with three real data sets are also reported.
292 citations
TL;DR: In this article, the effect of microwave pretreatment of fruit raw material on some physical properties of the orange tissue was investigated and it was found that microwave heating led to destruction of the parenchymal cells.
264 citations
TL;DR: It is concluded that ageing is accompanied by a functional dysregulation of motor cortex excitability during sensorimotor processing, with this deficit becoming progressively evident with greater task complexity.
Abstract: The objective of the present study was to identify the origin(s) of ageing-related behavioural slowing in sensorimotor tasks. For this aim, event-related potentials (ERPs) were analysed at 64 electrodes to evaluate the strength and timing of different stages of information processing in the brain. Electrophysiological indices of stimulus processing, sensorimotor integration/response selection and motor-related processing were used to compare the processing speed of young (n = 13, mean age = 22.5 years) and older adults (n = 14, mean age = 58.3 years) in simple- and choice-reaction tasks presented in two modalities, auditory and visual. The behavioural results showed significant ageing-related slowing, but only in the choice-reaction task. The quantification of separate central processing stages, in combination with advanced ERP methodology, helped to reveal that this slowing did not originate from the early processes of stimulus processing and response selection. Instead, it was produced by slower activation patterns over the contralateral motor cortex underlying response generation. It is concluded that ageing is accompanied by a functional dysregulation of motor cortex excitability during sensorimotor processing, with this deficit becoming progressively evident with greater task complexity.
232 citations
TL;DR: It is demonstrated that error-specific signals do exist in the brain and more importantly, error detection may occur in multiple functional systems operating in parallel at different levels of behavioral control.
213 citations
TL;DR: It is found that generalized gradient approximations (GGAs) and the B3LYP hybrid functional provide geometries in good agreement with experiment and with CASSCF calculations provided sufficiently extended basis sets are used.
Abstract: A comparison of density functionals is made for the calculation of energy and geometry differences for the high- [(5)T(2g): (t(2g))(4)(e(g))(2)] and low- [(1)A(1g): (t(2g))(6)(e(g))(0)] spin states of the hexaquoferrous cation [Fe(H(2)O)(6)](2+). Since very little experimental results are available (except for crystal structures involving the cation in its high-spin state), the primary comparison is with our own complete active-space self-consistent field (CASSCF), second-order perturbation theory-corrected complete active-space self-consistent field (CASPT2), and spectroscopy-oriented configuration interaction (SORCI) calculations. We find that generalized gradient approximations (GGAs) and the B3LYP hybrid functional provide geometries in good agreement with experiment and with our CASSCF calculations provided sufficiently extended basis sets are used (i.e., polarization functions on the iron and polarization and diffuse functions on the water molecules). In contrast, CASPT2 calculations of the low-spin-high-spin energy difference DeltaE(LH)=E(LS)-E(HS) appear to be significantly overestimated due to basis set limitations in the sense that the energy difference of the atomic asymptotes ((5)D-->(1)I excitation of Fe(2+)) are overestimated by about 3000 cm(-1). An empirical shift of the molecular DeltaE(LH) based upon atomic calculations provides a best estimate of 12 000-13 000 cm(-1). Our unshifted SORCI result is 13 300 cm(-1), consistent with previous comparisons between SORCI and experimental excitation energies which suggest that no such empirical shift is needed in conjunction with this method. In contrast, after estimation of incomplete basis set effects, GGAs with one exception underestimate this value by 3000-4000 cm(-1) while the B3LYP functional underestimates it by only about 1000 cm(-1). The exception is the GGA functional RPBE which appears to perform as well as or better than the B3LYP functional for the properties studied here. In order to obtain a best estimate of the molecular DeltaE(LH) within the context of density functional theory (DFT) calculations we have also performed atomic excitation energy calculations using the multiplet sum method. These atomic DFT calculations suggest that no empirical correction is needed for the DFT calculations.
178 citations
TL;DR: A reentrant novel phase is observed in the hexagonal ferroelectric HoMnO3 in the presence of magnetic fields in the temperature range defined by a plateau of the dielectric constant anomaly.
Abstract: A reentrant novel phase is observed in the hexagonal ferroelectric HoMnO3 in the presence of magnetic fields in the temperature range defined by a plateau of the dielectric constant anomaly. The plateau evolves with fields from a narrow dielectric peak at the Mn-spin rotation transition at 32.8 K in zero field. The anomaly appears both as a function of temperature and as a function of magnetic field without detectable hysteresis. This is attributed to the indirect coupling between the ferroelectric (FE) and antiferromagnetic (AFM) orders, arising from an FE-AFM domain wall effect.
TL;DR: The data suggest that SA antagonizes Pq effects, via elicitation of an antioxidative response in barley plants, and is highly expressed on DHAR and POX activity.
TL;DR: In this paper, the authors investigated the catalytic activity, long-term stability and the reasons for deactivation of a nanosize gold-supported Au/TiO2 in CO oxidation.
Abstract: The activity, long-term stability and the reasons for deactivation of a nanosize gold- supported Au/TiO2 in CO oxidation were investigated. Characterization of the catalyst sample was made by XPS, FTIR, TEM, BET, “depletive” oxidation and TPD instrumental methods. In spite of the experimentally proved very high activity at temperatures below 213 K, the catalyst exhibited a gradual decrease in initial activity. Two main reasons for the catalyst deactivation were found: (i) capability to adsorb CO and accumulate it as carbonates, this deactivation is reversible and after heating the catalyst surface is restored by CO2 evolution; (ii) agglomeration of Au particles, which causes irreversible, however weak deactivation.
TL;DR: In this paper, the effects of soil flooding on the activity of foliar antioxidative enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxide (APX), and glutathione reductase (GR) of barley plants ( Hordeum vulgare cv. Alfa ) were studied.
TL;DR: The reaction to the oxidative component of freezing in several tobacco lines, transformed with genes coding for enzymes involved in the synthesis of osmoprotectants along with their wild type, could serve as a good prerequisite for additional studies to gain further insights into the complex role of oSMoprotectionants in freezing tolerance.
TL;DR: The enol imine ⇄ enaminone tautomerization constants, KT, and thermodynamic parameters, ΔHT and ΔST, of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy as discussed by the authors.
Abstract: The enol imine ⇄ enaminone tautomerization constants, KT, and thermodynamic parameters, ΔHT and ΔST, of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy. Polar solvents shift the equilibrium toward the quinone form (for the unsubstituted derivative 1c, KT = 0.20 (cyclohexane) and KT = 1.49 (ethanol)). Both donor (MeO, NMe2) and acceptor (CN, NO2) substituents lead to a decreased KT independent of solvent polarity. In apolar solvents, for all derivatives 1a−1e, the enol imine ⇄ enaminone equilibria are endergonic but exothermic. Linear solvation energy relationships allow extrapolation of ΔGT to the gas phase. Density functional theory calculations (B3LYP/6-311+G**) yield good agreement with these extrapolated ΔGT values. Solvent effects on 1c are also successfully reproduced by the calculations. Geometric (O···N distance) and energetic criteria (conformer energy differences, homodesmotic reactions) establish the importance of intramolecular hydrogen bonding for the tautomerism...
TL;DR: The phase-mineral and chemical composition of ceramic cenosphere (CCCs) and water-soluble salt concentrates recovered from five fly ashes (FAs) produced in four large Spanish thermo-electric power stations was characterized as mentioned in this paper.
TL;DR: In this article, QCD results obtained from a study of hadronic event structure in high energy e^+e^- interactions with the L3 detector are presented, and the main results concern the measurement of the strong coupling constant, \alpha_s, from hadronic events shapes and the study of effects of soft gluon coherence through charged particle multiplicity and momentum distributions.
TL;DR: In this article, a cross-flow rig with tetraoctylammonium bromide and docosane in toluene was used for solvent stable nanofiltration.
TL;DR: In this article, a critical point symmetry for the prolate to oblate shape phase transition is introduced, starting from the Bohr Hamiltonian and approximately separating variables for γ = 30°.
TL;DR: In this paper, a mesoporous titania with high surface area and uniform pore size distribution was synthesized using surfactant templating method through a neutral [C 13 (EO) 6 -Ti(OC 3 H 7 ) 4 ] assembly pathway.
Abstract: Mesoporous titania with high surface area and uniform pore size distribution was synthesized using surfactant templating method through a neutral [C 13 (EO) 6 –Ti(OC 3 H 7 ) 4 ] assembly pathway. The different gold content (1–5 wt.%) was supported on the mesoporous titania by deposition–precipitation (DP) method. The catalysts were characterized by X-ray diffraction, TEM, SEM, N 2 adsorption analysis and TPR. The catalytic activity of gold supported mesoporous titania was evaluated for the first time in water–gas shift reaction (WGSR). The influence of gold content and particle size on the catalytic performance was investigated. The catalytic activity was tested at a wide temperature range (140–300 °C) and at different space velocities and H 2 O/CO ratios. It is clearly revealed that the mesoporous titania is of much interest as potential support for gold-based catalyst. The gold/mesoporous titania catalytic system is found to be effective catalyst for WGSR.
TL;DR: In this article, the lactic acid extraction by tri-n-octylamine dissolved in decanol and docecane has been studied and a mathematical model of extraction, taking into account formation of acid/amine complexes, has been composed and solved.
TL;DR: Negative mode ESI-MS fingerprinting method is capable of discerning distinct composition patterns to typify, to screen the sample origin and to reveal characteristic details of the more polar and acidic chemical components of propolis samples from different regions of the world.
Abstract: Crude ethanolic extracts of propolis, a natural resin, have been directly analysed using electrospray ionization mass (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) in the negative ion mode. European, North American and African samples have been analyzed, but emphasis has been given to Brazilian propolis which displays diverse and region-dependent chemical composition. ESI-MS provides characteristic fingerprint mass spectra, with propolis samples being divided into well-defined groups directly related to their geographical origins. Chemometric multivariate analysis statistically demonstrates the reliability of the ESI-MS fingerprinting method for propolis. On-line ESI-MS/MS tandem mass spectrometry of characteristic [M − H]− ion markers provides an additional dimension of fingerprinting selectivity, while structurally characterizing the ESI-MS marker components of propolis. By comparison with standards, eight such markers have been identified: para-coumaric acid, 3-methoxy-4-hydroxycinnamaldehyde, 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyran, 3-prenyl-4-hydroxycinnamic acid, chrysin, pinocembrin, 3,5-diprenyl-4-hydroxycinnamic acid and dicaffeoylquinic acid. The negative mode ESI-MS fingerprinting method is capable of discerning distinct composition patterns to typify, to screen the sample origin and to reveal characteristic details of the more polar and acidic chemical components of propolis samples from different regions of the world.
TL;DR: Evidence is presented that the absence of O antigen in the outer membrane of Yersinia either directly or indirectly, for example through a cellular or membrane stress, could act as a regulatory signal.
Abstract: Summary Lipopolysaccharide (LPS) is the major component of the outer membrane of Gram-negative bacteria. Although much attention has been given to the biological effects of its lipid A portion, a great body of evidence indicates that its O chain polysaccharide (O antigen) portion plays an important role in the bacterium‐host interplay. In this work we have studied in-depth the role of the O antigen in Yersinia enterocolitica serotype O:8 pathogenesis. We made a detailed virulence analysis of three mutants having different O antigen phenotypes: (i) LPS with no O antigen (rough mutant); (ii) LPS with one O unit (semirough mutant) and (iii) LPS with random distribution of O antigen chain lengths. We demonstrated that these LPS O antigen mutants were attenuated in virulence regardless of the infection route used. Coinfection experiments revealed that the rough and semirough mutants were severely impaired in their ability to colonize the Peyer’s patches and in contrast to the wild-type strain they did not colonize spleen and liver. The mutant with random distribution of O antigen chain lengths, however, survived better but started to be cleared from mouse organs after 8 days. As an explanation to this attenuation we present here evidence that other Yersinia virulence factors depend on the presence of O antigen for their proper function and/or expression. We demonstrated that in the rough mutant: (i) the YadA function but not its expression was altered; (ii) Ail was not expressed and (iii) inv expression was downregulated. On the other hand, expression of flhDC , the flagellar master regulatory operon, was upregulated in this mutant with a concomitant increase in the production of flagellins. Finally, expression of yplA , encoding for the Yersinia phospholipase A, was also upregulated accompanied by an increased flagellar type III secretion system mediated secretion of YplA to culture medium. Together these findings suggest that the absence of O antigen in the outer membrane of Yersinia either directly or indirectly, for example through a cellular or membrane stress, could act as a regulatory signal.
TL;DR: In this paper, a modified deposition-precipitation (MDP) method was used for the preparation of gold/ceria catalysts and the results showed significant differences in the low-temperature water-gas shift (WGS) activity of both catalysts.
Abstract: Gold/ceria catalysts were prepared by two different methods (deposition-precipitation and modified deposition-precipitation). Considerable differences in the low-temperature water-gas shift (WGS) activity of both catalysts were observed. The preparation technique strongly influenced catalytic activity due to the large differences in gold particles size and to the availability of active gold sites in close contact with ceria defects on the surface. HRTEM and EDS have shown presence of very highly dispersed gold clusters ( d about 1 nm) on the surface of the catalyst prepared by deposition-precipitation. Large gold particles (average d ≈15 nm) have been found in gold/ceria catalyst prepared by modified deposition-precipitation. FTIR spectroscopy of adsorbed CO and X-ray photoelectron spectroscopy were employed to obtain information about the surface structure of both catalysts and to explain the differences in catalytic activity.
TL;DR: In this article, the role of endogenous isoprene against oxidative stress caused by singlet oxygen ( 1 O 2 ) was studied in the isoprone-emitting plant Phragmites australis.
Abstract: The possible protective role of endogenous isoprene against oxidative stress caused by singlet oxygen ( 1 O 2 ) was studied in the isoprene-emitting plant Phragmites australis. Leaves emitting isoprene and leaves in which isoprene synthesis was inhibited by fosmidomycin were exposed to increasing concentrations of 1 O 2 generated by Rose Bengal (RB) sensitizer at different light intensities. In isoprene-emitting leaves, photosynthesis and H 2 O 2 and malonyldialdehyde (MDA) contents were not affected by low to moderate 1 O 2 concentrations generated at light intensities of 800 and 1240 μmol m -2 s -1 , but symptoms of damage and reactive oxygen accumulation started to be observed when high levels of 1 O 2 were generated by very high light intensity (1810 μmol m -2 s -1 ). A dramatic decrease in photosynthetic performance and an increase in H 2 O 2 and MDA levels were measured in isoprene-inhibited RB-fed leaves, but photosynthesis was not significantly inhibited in leaves in which the isoprene leaf pool was reconstituted by fumigating exogenous isoprene. The inhibition of photosynthesis in isoprene-inhibited leaves was linearly associated with the light intensity and with the consequently formed 1 O 2 . Hence, physiological levels of endogenous isoprene may supply protection against 1 O 2 . The protection mechanisms may involve a direct reaction of isoprene with 1 O 2 . Moreover, as it is a small lipophilic molecule, it may assist hydrophobic interactions in membranes, resulting in their stabilization. The isoprene-conjugated double bond structure may also quench 1 O 2 by facilitating energy transfer and heat dissipation. This action is typical of other isoprenoids, but we speculate that isoprene may provide a more dynamic protection mechanism as it is synthesized promptly when high light intensity produces 1 O 2 .
TL;DR: In this paper, magnetic studies of anthropogenic magnetic phases in road dust from the industrial zone of Visakhapatnam city (India) reveal the presence of large anthropogenic spherules with diameters up to ∼300 μm.
Abstract: Magnetic methods provide a fast tool for delineation of industrial pollution. Mineral magnetic studies of anthropogenic magnetic phases in road dust from the industrial zone of Visakhapatnam city (India) reveal the presence of large anthropogenic spherules with diameters up to ∼300 μm. Different internal structures of the spherules and a wide variation in size of the spherules, as well as the presence of melt-like particles and irregular shaped grains containing heavy metals, point to multiple sources of pollution, including different industries and heavy vehicle traffic. Magnetic mineralogy of the samples is dominated by a magnetite-like phase. Hysteresis parameters measured for magnetic extracts and single grains, are typical for pseudo-single domain magnetite. This is in disagreement with the large grain size of the single particles. Scanning electron microscopy images reveals a complex internal structure, showing an agglomeration of smaller grains and in-part, an extreme porosity of the spherules, probably related to fast cooling. The chemical composition determined by energy dispersive X-ray analysis is strongly variable and can also be very heterogeneous within a particle. First order reversal curve analysis indicates a spectrum of single domain, pseudo-single domain and multidomain properties. Values of saturation magnetisation suggest that the particles either consist of mainly similar ferrimagnetic sub-grains, whereas others are a mixture of ferrimagnetic and non-magnetic phases. Several irregular grains, showing a ferrimagnetic behaviour, contain a large amount of chromium (>50 wt%). The variations of the magnetic susceptibility along the three major roads in the industrial zone of Visakhapatnam are interpreted in terms of the relative degree of pollution.
15 Sep 2004
TL;DR: The evaluation exercise has highlighted some difficulties in assessing definition questions and can be improved in the future, but the overall analysis of submissions shows encouraging results as mentioned in this paper. But the evaluation process has been criticised in the past.
Abstract: Following the pilot Question Answering Track at CLEF 2003, a new evaluation exercise for multilingual QA systems took place in 2004. This paper reports on the novelties introduced in the new campaign and on participants' results. Almost all the cross-language combinations between nine source languages and seven target languages were exploited to set up more than fifty different tasks, both monolingual and bilingual. New types of questions (How- questions and definition questions) were given as input to the participating systems, while just one exact answer per question was allowed as output. The evaluation exercise has highlighted some difficulties in assessing definition questions and can be improved in the future, but the overall analysis of submissions shows encouraging results.
TL;DR: The hypothesis is that the PLA(2), apart from its role in second messenger generation, might play a direct and general role in the vesiculation processes underlying the intermembrane transport of rafts through purely physicochemical mechanisms.
TL;DR: In the Eastern Rhodope Eo-Oligocene mafic magmatism as discussed by the authors, the authors have shown that some form of convective removal of the lithosphere and mantle diapisism provide the most satisfactory explanation for the Paleogene structural and magmatic evolution.