Showing papers by "University of Ljubljana published in 1999"
01 Jan 1999
TL;DR: Some approaches to analysis and visualisation of large networks implemented in programPajek are presented and some typical examples are also given.
Abstract: Large networks, having thousands of vertices and lines, can be found in many different areas, e. g: genealogies, flo w graphs of programs, molecule, computer networks, transportation networks, social networks, intra/inter organisational networks ... Many standard network algorithms are very time and space consuming and therefore unsuitable for analysis of such networks. In the article we present some approaches to analysis and visualisation of large networks implemented in programPajek. Some typical examples are also given.
1,505 citations
TL;DR: In this paper, the idea of using inelastic demand spectra within the capacity spectrum method has been elaborated and is presented in an easy to use format, which represents the so-called N2 method formulated in the format of the Capacity Spectrum method.
Abstract: By means of a graphical procedure, the capacity spectrum method compares the capacity of a structure with the demands of earthquake ground motion on it. In the present version of the method, highly damped elastic spectra have been used to determine seismic demand. A more straightforward approach for the determination of seismic demand is based on the use of the inelastic strength and displacement spectra which can be obtained directly by time-history analyses of inelastic SDOF systems, or indirectly from elastic spectra. The advantages of the two approaches (i.e. the visual representation of the capacity spectrum method and the superior physical basis of inelastic demand spectra) can be combined. In this paper, the idea of using inelastic demand spectra within the capacity spectrum method has been elaborated and is presented in an easy to use format. The approach represents the so-called N2 method formulated in the format of the capacity spectrum method. By reversing the procedure, a direct displacement-based design can be performed. The application of the modified capacity spectrum method is illustrated by means of two examples. Copyright © 1999 John Wiley & Sons, Ltd.
774 citations
TL;DR: The results indicate that sandblasting may provide a powerful technique for strengthening Y-TZP in clinical practice and grinding may lead to substantial strength degradation and reduced reliability of prefabricated zirconia elements, therefore, sandblasted of ground surfaces is suggested.
724 citations
TL;DR: It was demonstrated that endothelial activity is a rhythmic process that contributes to oscillations in blood flow with a characteristic frequency of around 0.01 Hz, illustrating the potential of laser Doppler flowmetry combined with dynamical systems analysis for studies of both the micro- and macroscopic mechanisms of blood flow regulation in vivo.
Abstract: The wavelet transform technique, a time-frequency method with logarithmic frequency resolution, was used to analyze oscillations in human peripheral blood flow measured by laser Doppler flowmetry. The oscillations extended over a wide frequency state and their periods varied in time. Within the frequency range studied, 0.0095-1.6 Hz, five characteristic oscillations were revealed, arising from both local and central regulatory mechanisms. After the insertion of endothelium-dependent and endothelium-independent vasodilators the spectra of blood how markedly differed in the frequency interval 0.0095-0.02 Hz. In this way it was demonstrated that endothelial activity is a rhythmic process that contributes to oscillations in blood flow with a characteristic frequency of around 0.01 Hz. The study illustrates the potential of laser Doppler flowmetry combined with dynamical systems analysis for studies of both the micro- and macroscopic mechanisms of blood flow regulation in vivo.
613 citations
TL;DR: Solid-phase microextraction (SPME) as mentioned in this paper is a sample preparation technique that minimizes the consumption of organic solvents and has been shown to be useful in analytical chemistry.
Abstract: In recent years, much attention in analytical chemistry has been paid to sample preparation techniques, especially those which minimise the consumption of organic solvents One of the most promising of these, solid-phase microextraction (SPME), is presented in both its theoretical and practical aspects Conditions which affect its performance are assessed, as are the problems which may arise from its use Finally, some typical applications are listed, highlighting the method's sensitivity and precision, and the range of samples where SPME can be used successfully
526 citations
24 Jun 1999
TL;DR: This paper develops a unifying view on some of the existing measures for predictive and descriptive induction by means of contingency tables, and demonstrates that many rule evaluation measures developed for predictive knowledge discovery can be adapted to descriptive knowledge discovery tasks.
Abstract: Numerous measures are used for performance evaluation in machine learning. In predictive knowledge discovery, the most frequently used measure is classification accuracy. With new tasks being addressed in knowledge discovery, new measures appear. In descriptive knowledge discovery, where induced rules are not primarily intended for classification, new measures used are novelty in clausal and subgroup discovery, and support and confidence in association rule learning. Additional measures are needed as many descriptive knowledge discovery tasks involve the induction of a large set of redundant rules and the problem is the ranking and filtering of the induced rule set. In this paper we develop a unifying view on some of the existing measures for predictive and descriptive induction. We provide a common terminology and notation by means of contingency tables. We demonstrate how to trade off these measures, by using what we call weighted relative accuracy. The paper furthermore demonstrates that many rule evaluation measures developed for predictive knowledge discovery can be adapted to descriptive knowledge discovery tasks.
422 citations
TL;DR: The results indicate that buckwheat could be an important nutritional source of flavonoids, especially in countries with a low mean daily flavonoid intake.
Abstract: The content of the flavonoid rutin was determined in different milling fractions of buckwheat seeds and in buckwheat stems, leaves, and flowers. The extraction was performed by using a solvent containing 60% of ethanol and 5% of ammonia in water. The extracts were analyzed by capillary electrophoresis (running buffer of 50 mM borate (pH 9.3), 100 mM sodium dodecyl sulfate; determination at 380 nm). In bran fractions the concentration of rutin was 131-476 ppm, and in flour fractions 19-168 ppm. On average, about 300, 1000, and 46000 ppm of rutin were found in leaves, stems, and flowers, respectively. The results indicate that buckwheat could be an important nutritional source of flavonoids, especially in countries with a low mean daily flavonoid intake.
272 citations
TL;DR: In this article, the first results of a benchmark problem concerning the simulation of coupled natural convection and melting from an isothermal vertical wall are presented in detail and show that, while qualitative agreement is obtained in most situations, it is still relevant to proceed to thorough numerical comparisons before assessing the accuracy of the different algorithms.
229 citations
TL;DR: Data obtained show that even 10 years after closure of the Hg mine, Hg concentrations in river sediments and water are still very high and did not show the expected decrease of Hg in the Gulf of Trieste.
209 citations
TL;DR: Particles from gas saturated solutions, a novel method for high pressure material processing, has been used for micronization of practically insoluble calcium-channel blockers nifedipine and felodipines and the hypolipidemic agent fenofibrate with the aim of increasing their dissolution rate and hence their bioavailability.
178 citations
TL;DR: To investigate possible differences in the manifestations of Lyme borreliosis in Europe and the United States, epidemiologic, demographic, clinical, and laboratory findings in patients from New York State and patients from Slovenia who had microbiologically confirmed erythema migrans caused by B. burgdorferi were compared.
Abstract: Erythema migrans caused by Borrelia afzelii in Slovenia and erythema migrans caused by B. burgdorferi in New York have distinct clinical presentations. Caution should be used when clinical and labo...
TL;DR: The algorithms in this paper are designed such that they can easily be generalised to other kinds of dependencies, and the bottom-up algorithm is the most efficient of the three, and also outperforms other algorithms from the literature.
Abstract: Database dependencies, such as functional and multivalued dependencies, express the presence of structure in database relations, that can be utilised in the database design process. The discovery of database dependencies can be viewed as an induction problem, in which general rules (dependencies) are obtained from specific facts (the relation). This viewpoint has the advantage of abstracting away as much as possible from the particulars of the dependencies. The algorithms in this paper are designed such that they can easily be generalised to other kinds of dependencies.Like in current approaches to computational induction such as inductive logic programming, we distinguish between top-down algorithms and bottom-up algorithms. In a top-down approach, hypotheses are generated in a systematic way and then tested against the given relation. In a bottom-up approach, the relation is inspected in order to see what dependencies it may satisfy or violate. We give a simple (but inefficient) top-down algorithm, a bi-directional algorithm, and a bottom-up algorithm. In the case of functional dependencies, these algorithms have been implemented in the FDEP system and evaluated experimentally. The bottom-up algorithm is the most efficient of the three, and also outperforms other algorithms from the literature.
TL;DR: Comparison of some faunas shows that the limiting factors for biodiversity might be the lower ecological diversity of habitats and restricted food resources underground, both brought about to a high degree by the darkness and absence of plants.
Abstract: The specialised aquatic hypogean, i.e. stygobiotic, fauna has been recognised in some regions moderately rich. Slovenia, the broader Dinaric region, and Europe are particularly rich with about 7-8% of all Metazoa and about 40% of Crustacea species being stygobionts. The hypogean biotic diversity is in general predominantly a crustacean diversity. The high number of stygobiont Crustacea-Malacostraca species can be explained by the near absence of Insecta as well as by their high endemicity and some- times additional specialisation, i.e. the spatial and ecological partition of the environment by the species. Although one cave system may exceptionally shelter up to 40 stygobiont species, they are distributed there into separate associations. Among more than 2000 described stygobiontic Malacostraca species, which include close to 950 Amphipoda, the species numbers within some genera are very high (e.g. Niphargus with 275 spp.). With 10 orders represented the higher taxonomic diversity of stygobiont Malacostraca matches that of fresh waters or the sea. Comparison of some faunas shows that the limiting factors for biodiversity might be the lower ecological diversity of habitats and restricted food resources underground, both brought about to a high degree by the darkness and absence of plants. Being K-strategists, stygobionts are endangered by any sudden changes in their environment. In the case of an increased food input by modest organic pollution, they can be outcompeted by energetically demanding but competitively stronger recent immigrants from surface.
TL;DR: The ROC analysis shows significant improvements of sensitivity and specificity compared to the performance of the clinicians and it is shown that the predictive power of standard tests with that of machine learning techniques can be significantly improved.
TL;DR: The results suggest that rep-PCR can provide an alternative method for L. monocytogenes typing and suggest that REP and ERIC elements can be used for typing enterobacterial repetitive intergenic consensus sequences.
Abstract: Listeria monocytogenes strains possess short repetitive extragenic palindromic (REP) elements and enterobacterial repetitive intergenic consensus (ERIC) sequences. We used repetitive element sequence-based PCR (rep-PCR) to evaluate the potential of REP and ERIC elements for typing L. monocytogenes strains isolated from humans, animals, and foods. On the basis of rep-PCR fingerprints, L. monocytogenes strains were divided into four major clusters matching origin of isolation. rep-PCR fingerprints of human and animal isolates were different from those of food isolates. Computer evaluation of rep-PCR fingerprints allowed discrimination among the tested serotypes 1/2a, 1/2b, 1/2c, 3b, and 4b within each major cluster. The index of discrimination calculated for 52 epidemiologically unrelated isolates of L. monocytogenes was 0.98 for REP- and ERIC-PCR. Our results suggest that rep-PCR can provide an alternative method for L. monocytogenes typing.
TL;DR: In this paper, a phenomenological expression for the energy of the interaction between an inclusion and local curvature of the surrounding membrane is proposed, and assuming thermodynamic equilibrium, the free energy of inclusions, and the consistently related lateral and orientational distributions of the inclusions are obtained using statistical mechanical methods.
Abstract: Phospholipid membrane forming a closed surface and decorated with anisotropic inclusions is considered. The inclusions are free to redistribute laterally over the membrane and to orient in the plane of the membrane according to the local membrane curvature. A phenomenological expression for the energy of the interaction between an inclusion and local curvature of the surrounding membrane is proposed. Considering this single-inclusion energy, and assuming thermodynamic equilibrium, the free energy of the inclusions, and the consistently related lateral and orientational distributions of the inclusions are obtained using statistical mechanical methods. For a vesicle shape with given surface area, enclosed volume, and total amount of inclusions, the free energy is in general given in a nonlocal form (i.e. it can not be expressed as an integral of its area density over the membrane area). The limits of weak and strong orientational ordering are considered. Specifically, it is shown that in the shape sequence representing the formation of an exovesicle the effect of the membrane curvature on the orientation of the inclusions may stabilize the shape where the exovesicle and the cell are connected by a narrow neck.
TL;DR: It is demonstrated that Dobrava and Puumala viruses coexist in a single region of endemicity and are capable of causing HFRS with significant differences in severity.
Abstract: This report describes the first investigation of clinical findings for a larger series of patients with hemorrhagic fever with renal syndrome (HFRS) who were infected with Dobrava virus. From 1985 to 1995, 38 patients with serologically confirmed HFRS were hospitalized at the regional hospital in Novo mesto in the Dolenjska region of Slovenia. On the basis of results of serological examination, 24 patients had Dobrava virus infection, and 14 patients had Puumala virus infection. Complete clinical data were available for 31 patients. Eleven patients underwent hemodialysis for treatment of acute oliguric or anuric renal failure. Four patients, all infected by Dobrava virus, had signs of shock and severe bleeding. Three severely ill Dobrava virus-infected patients died of hemorrhagic complications. We have demonstrated that Dobrava and Puumala viruses coexist in a single region of endemicity and are capable of causing HFRS with significant differences in severity.
TL;DR: It is proven that small vesicles are not stable and disintegrate immediately in contact with other surfaces, they lose an important influence on the topical delivery of the entrapped hydrophilic substances.
TL;DR: The dependence of the aggregation phenomena on the chain length of the surfactant (n = 12, 14, 16, 18) and on the ionic strength of solutions was investigated by fluorescence and conductivity measurements at 25 °C.
Abstract: Micelle formation of alkyltrimethylammonium surfactants (CnTMAB) in aqueous sodium poly(styrenesulfonate) (NaPSS) solutions was studied by fluorescence and conductivity measurements at 25 °C. The dependence of the aggregation phenomena on the chain length of the surfactant (n = 12, 14, 16, 18) and on the ionic strength of solutions was investigated. The critical aggregation concentration (cac) decreases with increasing hydrophobicity of the surfactant but remains approximately unchanged for C16TMAB and C18TMAB. The cac values are considerably lower than the critical micellization concentration (cmc) values for the same surfactant. The decrease is in the range from about three orders of magnitude for C12EDMAB in water to approximately 10 times for C18TMAB in 0.01 M NaBr. Furthermore, the cac for C12EDMAB and C14TMAB in NaPSS was found to increase slightly with increasing NaBr concentration but much less than, for instance, in sodium poly(acrylate) solutions. No significant effect of NaBr on cac values for ...
TL;DR: Procathepsin B autoactivation is pH‐dependent with a pH optimum at 4.5 and with no processing observed at pH>6.0, but in the presence of 0.5 μg/ml of dextran sulfate, relatively rapid processing is observed even at pH 6.5 (t 1/2∼90 min), suggesting that glycosaminoglycans are involved in in vivo processing of lysosomal cysteine proteases.
TL;DR: In this paper, an audit of 24 school buildings in Slovenia showed that the nominal heating power of boilers, and heat exchangers, which are used in district heating, showed a 57% overcapacity and the heat losses of the school buildings are 89% higher than the recommended values.
TL;DR: In this article, it was shown that planar and outerplanar graphs are (3, 2 )-choosable with impropriety d and (m, d)-choosability, respectively, if each vertex of G has at most d neighbours coloured with the same colour as itself.
Abstract: A graph G is m-choosable with impropriety d, or simply (m, d)*-choosable, if for every list assignment L, where ∣L(v)∣≥m for every v∈V(G), there exists an L-colouring of G such that each vertex of G has at most d neighbours coloured with the same colour as itself. We show that every planar graph is (3, 2)*-choosable and every outerplanar graph is (2, 2)*-choosable. We also propose some interesting problems about this colouring.
TL;DR: A diagnostic procedure was developed to predict soon after accidents which incomplete SCI patients are candidates for permanent use of a functional electrical stimulation (FES) orthotic aid.
Abstract: After a program of therapeutic electrical stimulation, 3 groups of incomplete spinal cord injured (SCI) patients were identified, those in whom an improvement of both voluntary and stimulated muscle force was observed, those with an increase in stimulation response only, and patients in whom no effect of electrical stimulation training could be recorded. As it is difficult to predict the outcome of the electrical stimulation rehabilitation process, a diagnostic procedure was developed to predict soon after accidents which incomplete SCI patients are candidates for permanent use of a functional electrical stimulation (FES) orthotic aid. The candidates for chronic use of FES are patients with weak ankle dorsiflexors and sufficiently strong knee extensors. These patients are equipped with a single channel peroneal stimulator augmenting dorsiflexion and knee and hip flexion in a total lower limb flexion response. By applying FES to the ankle plantar flexors, the swing phase of walking can be significantly shortened and faster walking obtained.
TL;DR: Analgesia is essential for successful completion of modern dental procedures and standard inferior alveolar nerve block (IANB) is the primary method used to achieve mandibular analgesia.
Abstract: Analgesia is essential for successful completion of modern dental procedures. Standard inferior alveolar nerve block (IANB) is the primary method used to achieve mandibular analgesia. Difficulty experienced in obtaining satisfactory analgesia after IANB, especially of an acutely inflamed mandibular molar, remains a common clinical problem. Even when a proper technique is employed, clinical studies show that IANB fails in approximately 30% to 45% of cases. The reasons for failure are not fully understood. Anatomical considerations and abnormal physiological responses in the presence of inflammation as explanations for IANB failure are discussed in this paper.
TL;DR: The core of a line defect with topological charge M=1 is uniaxial in the axial direction and it seems that the core of the point defect does not depend on the far nematic director field in the bulk limit.
Abstract: We study the biaxial structure of both line and point defects in a nematic liquid crystal confined within a capillary tube whose lateral boundary enforces homeotropic anchoring. According to Landau--de Gennes theory the local order in the material is described by a second-order tensor $\mathbf{Q},$ which encompasses both uniaxial and biaxial states. Our study is both analytical and numerical. We show that the core of a line defect with topological charge $M=1$ is uniaxial in the axial direction. At the lateral boundary, the uniaxial ordering along the radial direction is reached in two qualitatively different ways, depending on the sign of the order parameter on the axis. The point defects with charge $M=\ifmmode\pm\else\textpm\fi{}1$ exhibit a uniaxial ring in the plane orthogonal to the cylinder axis. This ring is in turn surrounded by a torus on which the degree of biaxiality attains its maximum. The typical lengths that characterize the structure of these defects depend both on the cylinder radius and the biaxial correlation length. It seems that the core of the point defect does not depend on the far nematic director field in the bulk limit.
TL;DR: In this article, the viscosities of aqueous solutions of some poly(ethylene glycol)s (PEGs) with nominal molecular weights ranging from 300 to 35,000 g mol−1 were determined up to a concentration of 0.3 g cm−3 at 298.15 K. The viscosity coefficients B were evaluated and hence the partial molar Gibbs free energy of activation of viscous flow of solute at infinite dilution was calculated and interpreted in terms of the relative effects of the solute on the ground and transition state solvent.
TL;DR: The results show that the binary scale and the first presentation of measurement instruments are the least reliable, but surprisingly, the two data collection techniques yield equally reliable data.
TL;DR: An order parameter (charge stiffness D) is proposed which controls the phase transition from nonmixing and nonergodic dynamics to mixing and ergodic dynamics (disordered phase, D=0) in the thermodynamic limit.
Abstract: We study a generic but simple nonintegrable quantum many-body system of locally interacting particles, namely, a kicked-parameter (t,V) model of spinless fermions on a one-dimensional lattice (equivalent to a kicked Heisenberg XX-Z chain of 1/2 spins). The statistical properties of the dynamics (quantum ergodicity and quantum mixing) and the nature of quantum transport in the thermodynamic limit are considered as the kick parameters (which control the degree of nonintegrability) are varied. We find and demonstrate ballistic transport and nonergodic, nonmixing dynamics (implying infinite conductivity at all temperatures) in the integrable regime of zero or very small kick parameters, and more generally and importantly, also in the nonintegrable regime of intermediate values of kicked parameters, whereas only for sufficiently large kick parameters do we recover quantum ergodicity and mixing implying normal (diffusive) transport. We propose an order parameter (charge stiffness D) which controls the phase transition from nonmixing and nonergodic dynamics (ordered phase, D>0) to mixing and ergodic dynamics (disordered phase, D=0) in the thermodynamic limit. Furthermore, we find exponential decay of time correlation functions in the regime of mixing dynamics. The results are obtained consistently within three different numerical and analytical approaches: (i) time evolution of a finite system and direct computation of time correlation functions, (ii) full diagonalization of finite systems and statistical analysis of stationary data, and (iii) algebraic construction of quantum invariants of motion of an infinite system, in particular the time-averaged observables.
TL;DR: In this article, a coprecipitation method was used to synthesize catalytic wet oxidation of phenol in aqueous solutions, and the three most important synthesis parameters, the concentration of the mixed metal salt solution, the rate of cop-recipitant addition and the stirrer speed during coprecipient, were optimized with central composite design using the catalytic activity as a response function.
TL;DR: The model can be readily applied in clinical practice to estimate the stress distribution in the most frequent body positions of everyday activities by analyzing the data on the resultant hip force obtained from laboratory observations where a stance period of gait is considered.