Plamen Mateev

Footprint analysis of gait using a pressure sensor system.

The purpose of this study was to investigate if the detailed pressure data of the footprints of normal gait add essential information to the spatio-temporal variables of gait. The gait of 62 healthy adult subjects was investigated using GAITRite pressure sensor system. Each footprint was divided into 12 equal trapezoids and after that the hindfoot, midfoot and forefoot analysis was developed. A typical activation pattern of the sensors with two peaks of active area and peak pressure distribution during normal walking was obtained. The first peak reflected the heel strike, and the second peak reflected push-off at the end of the stance phase. The lowest pressure values were in the midfoot, where the lateral part of the foot activated sensors more than the medial part. The footprint patterns of right and left legs were symmetrical and corresponded with the symmetry found in the spatio-temporal variables of gait. The variability for the active area and the peak pressure were more pronounced for the lateral part of the midfoot and a smaller variation was seen in areas with concentrated observations (e.g. 1st, 2nd and 5th lateral trapezoids). Increasing active area in the forefoot was associated with decreasing pressure sensor activity in the midfoot. The footprint patterns identified the symmetry between the legs and at the same time revealed the velocity performance.

A Measure of Risk Caused by Information Asymmetry in e-Commerce

The problem of enhancing success in e-Commerce requires reducing or sharing the risk of misinforming. The objectives of this paper is to raise and discuss the difficulties in quantifying the risk of misunderstanding caused by information asymmetry in a communication process; and to propose a mathematical model, developed to measure the risk of misinforming. Usage of warranty, as the most popular tool of sharing risk, is discussed in the light of risks of misinforming. A data set collected in an experiment, was used to illustrate the major ideas proposed as well as to stress on the fact that in particular circumstances this kind of risk is not understood by clients, which often leads to wrong decisions.

Plant response to lead in the presence or absence EDTA in two sunflower genotypes (cultivated H. annuus cv. 1114 and interspecific line H. annuus × H. argophyllus)

The aim of the present work was to study the response of two sunflower genotypes (cultivated sunflower Helianthus annuus cv. 1114 and newly developed genotype H. annuus × Helianthus argophyllus) to Pb medium-term stress and the role of exogenously applied EDTA in alleviating Pb toxicity in hydroponics. Plant growth, morpho-anatomical characteristics of the leaf tissues, electrolyte leakage, total antioxidant activity, free radical scavenging capacity, total flavonoid content, and superoxide dismutase isoenzyme profile were studied by conventional methods. Differential responses of both genotypes to Pb supplied in the nutrient solution were recorded. Pb treatment induced a decrease in the relative growth rate, disturbance of plasma membrane integrity, and changes in the morpho-anatomical characteristics of the leaf tissues and in the antioxidant capacity, which were more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype demonstrated higher tolerance to Pb when compared with the cultivar. This was mainly due to increased photosynthetically active area, maintenance of plasma membrane integrity, permanently high total antioxidant activity, and free radical scavenging capacity as well as total flavonoid content. The addition of EDTA into the nutrient solution led to limitation of the negative impact of Pb ions on the above parameters in both genotypes. This could be related to the reduced content of Pb in the roots, stems, and leaves, suggesting that the presence of EDTA limited the uptake of Pb. The comparative analysis of the responses to Pb treatment showed that the deleterious effect of Pb was more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype H. annuus × H. argophyllus was more productive and demonstrated higher tolerance to Pb medium-term stress, which could indicate that it may possess certain mechanisms to tolerate high Pb concentrations. This character could be inherited from the wild parent used in the interspecific hybridization. The ability of EDTA to prevent Pb absorption by the plants could underly the mechanism of limiting of the negative impact of Pb ions. Hence, EDTA cannot be used to enhance Pb absorption from nutrient solution by sunflower plants for phytoremediation purposes.

Footprint peak time and functional ambulation profile reflect the potential for hemiparetic gait recovery.

Objective: Gait disturbances were monitored in patients with chronic stroke with a walkway built with pressure sensors in order to assess whether detailed gait and footprint information could provide verification for the potential for gait recovery. Methods: Gait variables (footprint peak times, temporal and spatial parameters and Functional Ambulation Profile, FAP, scores), were first recorded in 25 patients with chronic stroke at their preferred speed and 10 healthy volunteers walking from very slow to very fast. Patients and controls were divided into four groups based on the velocity performance. Secondly, the effect of rehabilitation on the footprint peak times was evaluated in another group of 20 chronic stroke patients. Results and conclusions: The footprint peak time behaviour of different patients with chronic stroke reflected their hemiparetic gait pattern. The slower patients had prolonged footprint peak times on the non-affected side (NS) and shorter values on the lateral footprint on the affected side (AS). The increased gait velocity and the FAP scores decreased the footprint peak times on both sides, especially on the NS. The rehabilitation increased the gait velocity with 18.2%, decreased the duration of the mid-foot and forefoot peak times on the NS and the lateral mid-foot peak times on the AS. A detailed analysis of the individual gait performance allows more accurate assessment of the potential for gait recovery.

Modeling the Distribution of Highly Volatile Exchange-rate Time Series

Modeling the unconditional distribution of returns on exchange rates is nontrivial, because they are typically fat-tailed and highly peaked around the center. Especially, the exchange rates of many Eastern European countries exhibit a highly volatile and seemingly erratic behavior in the initial phase of moving from controlled to freely floating exchange rates. In this paper we examine to what extend the distributional properties of such time series can be captured by certain types of stable distributions. We consider the standard stable Paretian distribution and special, thin-tailed members of the family of geometric summation stable distributions. An application to the Bulgarian lev/US dollar exchange-rate series reveals that among the candidates considered only the fat-tailed stable Paretian distribution is able to capture the characteristics of this highly volatile time series.

Warranty as a Factor for E-commerce Success

Two groups of factors impact the success of e-commerce transaction: environmental factors and content of the messages exchanged between the seller and the buyer. The first group includes factors describing the environment in which the seller-buyer relationship operates, such as IT infrastructure, Logistic Infr astructure, Financial Infrastructure, and Government regulations. Second group -content of the message -covers these elements of the message, which improve the trust between the two parties (especially the buyer’s trust). Among them, the statement about warranty plays critical role as the risk reducing information send by the seller. The two aspects of warranty message are considered: malfunctioning (the product does not operate as it is expected by the seller) and misinforming (the product does not operate as it is expected by the buyer).

Development of a real-time algorithm for detection of solar wind discontinuities

A study is presented of an algorithm, based on the statistical analysis of interplanetary magnetic field data, for the real-time detection of discontinuities in the solar wind. The analysis is based on the application of a ‘sliding’ or ‘searching’ algorithm together with a minimum variance treatment. A demonstration is given for a Pioneer data set from 29 August, 1966. This particular data set was chosen because it has been extensively studied (in terms of the fast forward MHD shock wave) by previous groups who utilized the three-dimensional Rankine-Hugoniot shock equations after identifying the shock on a subjective basis. Our procedure differs in that it is perfectly objective because of its ‘searching’ technique. For this particular data set we identify the original shock with excellent agreement with the earlier studies of its normal vector, as well as an additional shock and tangential discontinuity, neither of which had been identified previously.

Risk of Misinforming and Message Customization in Customer Related Management

This paper discusses applications of the measures of the risk of misinforming and the role of the warranty of misinforming in the context of the informing component of Customer Relationship Management (CRM) issues. This study consists of two parts. Firstly, we propose an approach for customers’ grouping based on their attitude toward assessing product’s properties and their expertise on the terminology/domain of the seller’s message describing the product. Also we discuss what the most appropriate personal/group warranty is for each of these group/clusters.