South-West University "Neofit Rilski"
Recent publications
The present paper proposes the use of platforms for modeling of communication networks, in particular modeling of IP networks. The study of IP networks, by using modeled IP networks, has many advantages, which are described in the work. The study of IP networks through modeled ones is shown in practice, through the GNS3 platform. Different capabilities of the proposed platform are presented when using modeled IP networks.
The placebo effect is a phenomenon of influencing certain clinical symptoms under the influence of drugs or medical manipulations that completely resemble the real ones. An increasing number of clinical trials on the effects of oral, parenteral and topical medications, as well as hardware procedures, are being conducted with placebo control groups to clarify the real clinical effect of the substances or methods used. Methods: A total of 30 patients with carpal tunnel syndrome were investigated. In our study, we compared the effect of actually applied low-frequency pulsed magnetic field treatment and Ultraphonophoresis with Contractubex in the carpal tunnel area with а placebo. Patients were informed in advance that some of them would fall into the placebo group but would not know which ones. Results and analysis: The result of the registration of the persons intended during the treatment in both groups and in the follow-up examination show that the pain is weaker at the end of the treatment course. Conclusion: The use of preformed factors gives better results in reducing the pain syndrome within the treatment course, but it is not more effective in the long run than using a placebo.
Glutamate is an excitatory neurotransmitter in the nervous system. Excessive glutamate transmission can lead to increased calcium ion expression, related to increased neurotoxicity. Memantine is used for treating patients with Alzheimer’s disease (AD) due to its protective action on the neurons against toxicity caused by over activation of N-methyl-D-aspartate receptors. Nootropics, also called “smart drugs”, are used for the treatment of cognitive deficits. In this work, we evaluate the neuroprotective action of four memantine analogues of glycine derivatives, including glycyl-glycine, glycyl-glycyl-glycine, sarcosine, dimethylglycine and three conjugates with nootropics, modafinil, piracetam and picamilon. The new structural memantine derivatives improved cell viability against copper-induced neurotoxicity in APPswe cells and glutamate-induced neurotoxicity in SH-SY5Y cells. Among these novel compounds, modafinil-memantine, piracetam-memantine, sarcosine-memantine, dimethylglycine-memantine, and glycyl-glycine-memantine were demonstrated with good EC50 values of the protective effects on APPswe cells, accompanied with moderate amelioration from glutamate-induced neurotoxicity. In conclusion, our study demonstrated that novel structural derivatives of memantine might have the potential to develop promising lead compounds for the treatment of AD. The solubility of memantine analogues with nootropics and memantine analogues with glycine derivatives in buffer solutions at pH 2.0 and pH 7.4 simulating the biological media at 298.15 K was determined and the mutual influence of the structural fragments in the molecules on the solubility behavior was analyzed. The significative correlation equations relating the solubility and biological properties with the structural HYBOT (Hydrogen Bond Thermodynamics) descriptors were derived. These equations would greatly simplify the task of the directed design of the memantine analogues with improved solubility and enhanced bioavailability.
Numerous wireless sensor networks (WSN) applications include monitoring and controlling various conditions in the environment, industry, healthcare, medicine, military affairs, agriculture, etc. The life of sensor nodes largely depends on the power supply type, communication ability, energy storage capacity and energy management mechanisms. The collection and transmission of sensor data streams from sensor nodes lead to the depletion of their energy. At the same time, the storage and processing of this data require significant hardware resources. Integration between clouds and sensor networks is an ideal solution to the limited computing power of sensor networks, data storage and processing. One of the main challenges facing systems engineers is to choose the appropriate protocol for integrating sensor data into the cloud structure, taking into account specific system requirements. This paper presents an experimental study on the effectiveness of integration between sensor networks and the cloud, implemented through three protocols HTTP, MQTT and MQTT-SN. A model for studying the integration of sensor network - Cloud with the communication models for integration - request-response and publish- subscribe, implemented with HTTP, MQTT and MQTT-SN. The influence of the number of transmitted data packets from physical sensors to the cloud on the transmitted data delay to the cloud, the CPU and memory load was studied. After evaluating the results of sensor network and cloud integration experiments, the MQTT protocol is the most efficient in terms of data rate and power consumption.
It is well known that the Hermann's Tortoise (Testudo hermanni) feeds primarily on plants. The species can also supplement its diet with different food sources, including carrion. Yet, few cases of scavenging behavior have been reported in the literature. Here we report on the consumption of a dead female Common Toad (Bufo bufo) by an adult female T. hermanni. The scavenging behavior observed can be related to the increased energy needs of females during the nesting season.
The active season of T. hermanni in Bulgaria is from March-April to October-November. So far, few cases of winter activity have been registered in the country. Here we report on another such case of an adult T. hermanni. The temporary emergence of the specimen from its hibernaculum was probably caused by the combined effect of several factors such as the high ambient temperatures, the orientation of the slope, the altitude, the depth of the hibernaculum used, etc.
Network connectivity characterises the ability to deliver data to the sensor network from a source node to a receiver node. A significant problem with these networks occurs when a sensor node fails, leading to a loss of network connectivity. In these cases, some network areas remain isolated, and therefore the nodes cannot transmit data to the central node. The paper presents and studies the characteristics of a sensor network(SN) with mesh topology, which reflects the ability of the network to establish connections between network elements within the geometric boundaries of the sensor field and the primary node (coordinator), accumulating data from all sensors in the network. The research aims to study the connectivity and reliability of sensor networks by identifying the interdependence of probabilistic energy characteristics. Well-known is the impact on these characteristics of the wireless sensor network parameters as geometric dimensions, distribution model of sensor devices in the sensor field, mesh network topology, and radio communication range.
Wireless sensor networks are distributed networks consisting of many tiny sensor nodes with limited resources. These networks play an extremely important role in people’s modern lives. Despite their great application, one of the critical issues in their design and operation is the security of sensor nodes, data, and entire network fragments. Security breaches through software attacks on sensor networks are currently the subject of much research by academia and the research community. Hardware Trojans (HTH) are malicious changes to hardware specifications during design or production in a way that alters the functionality of IC integrated circuits under conditions specified by the attacker. The discovery of HTH is a particularly difficult task in modern submicron technologies due to their intensive development. Our research shows that security threats and attacks based on hardware building sensor networks are real and not yet sufficiently studied, which is why this work focuses on the specifics of identifying this type of threat. The paper discusses and classifies hardware- specific hardware attacks. As a result of the study, some approaches to increase sensor networks’ hardware security have been identified and proposed. The results obtained in this work can be used to improve the means of protection of wireless sensor networks against various cyber-physical attacks.
In 2020, the health status of urban forests in Etropole and Pravets municipalities was monitored based on remote sensing data and field assessment. The study provides information for early detection and identification of pests and pathogens causing damage in different forest types. Three forest stands were assessed: Scots pine ( Pinus sylvestris ) plantation near the town of Etropole, European beech ( Fagus sylvatica ) natural stand near Etropole Monastery, and Quercus spp. coppice stands in ‘Nebesnite Pasbishta’ forest park near Osikovitsa village. In two sample plots (town of Etropole and Osikovitsa village), remote sensing data were obtained by a ‘Parrot Sequoia’ multispectral camera integrated with a specialized professional system eBee ‘Flying Wing’. Normalised difference vegetation index (NDVI) was assessed by digital mixing of imagery, captured in the red and near-infrared range. It was established that the Scots pine plantations were weakened, with NDVI values between 0.66 and 0.75. The oak stands in the area of Osikovitsa village were in better health condition (NDVI mainly 0.79-0.98). Symptoms of diseases and pest damage were found during the field verifications. Severe deterioration caused by the invasive fungal pathogen Dothistroma septosporum had destroyed the pine plantation near Etropole. The pathogen caused premature needle defoliation, resulting in loss of timber yield and, in severe cases, tree death. In oak stands, damage was caused mainly by the invasive insect pest – oak lace bug ( Corythucha arcuata ). In Fagus sylvatica forests damage was caused mainly by abiotic factors (snow and wind), and wood destroying fungus Fomes fomentarius .
Objective The aim of this study to examine the amount of the total variance of the subjective well-being (SWB) of psychotherapists from 12 European countries explained by between-country vs. between-person differences regarding its cognitive (life satisfaction) and affective components (positive affect [PA] and negative affect [NA]). Second, we explored a link between the SWB and their personal (self-efficacy) and social resources (social support) after controlling for sociodemographics, work characteristics, and COVID-19-related distress. Methods In total, 2915 psychotherapists from 12 countries (Austria, Bulgaria, Cyprus, Finland, Great Britain, Serbia, Spain, Norway, Poland, Romania, Sweden, and Switzerland) participated in this study. The participants completed the Satisfaction with Life Scale (SWLS), the International Positive and Negative Affect Schedule Short Form (I-PANAS-SF), the General Self-Efficacy Scale, and the Multidimensional Scale of Perceived Social Support. Results Cognitive well-being (CWB; satisfaction with life) was a more country-dependent component of SWB than affective well-being (AWB). Consequently, at the individual level, significant correlates were found only for AWB but not for CWB. Higher AWB was linked to being female, older age, higher weekly workload, and lower COVID-19-related distress. Self-efficacy and social support explained AWB only, including their main effects and the moderating effect of self-efficacy. Conclusions The results highlight more individual characteristics of AWB compared to CWB, with a more critical role of low self-efficacy for the link between social support and PA rather than NA. This finding suggests the need for greater self-care among psychotherapists with regard to their AWB and the more complex conditions underlying their CWB.
The aim of this study was to examine cross-cultural differences, as operationalized by Schwartz's refined theory of basic values, in burnout levels among psychotherapists from 12 European countries during the coronavirus disease (COVID-19) pandemic. We focused on the multilevel approach to investigate if individual- and country-aggregated level values could explain differences in burnout intensity after controlling for sociodemographic, work-related characteristics and COVID-19-related distress among participants. 2915 psychotherapists from 12 countries (Austria, Bulgaria, Cyprus, Finland, Great Britain, Serbia, Spain, Norway, Poland, Romania, Sweden, and Switzerland) participated in this study. The participants completed the Maslach Burnout Inventory-Human Service Survey, the revised version of the Portrait Values Questionnaire, and a survey questionnaire on sociodemographic, work-related factors and the COVID-19 related distress. In general, the lowest mean level of burnout was noted for Romania, whereas the highest mean burnout intensity was reported for Cyprus. Multilevel analysis revealed that burnout at the individual level was negatively related to self-transcendence and openness-to-change but positively related to self-enhancement and conservation values. However, no significant effects on any values were observed at the country level. Male sex, younger age, being single, and reporting higher COVID-19-related distress were significant burnout correlates. Burnout among psychotherapists may be a transcultural phenomenon, where individual differences among psychotherapists are likely to be more important than differences between the countries of their practice. This finding enriches the discussion on training in psychotherapy in an international context and draws attention to the neglected issue of mental health among psychotherapists in the context of their professional functioning.
In recent years, there has been a rapid development in the wearable industry. The growing number of wearables has led to the demand for new lightweight, flexible wearable antennas. In order to be applicable in IoT wearable devices, the antennas must meet certain electrical, mechanical, manufacturing, and safety requirements (e.g., specific absorption rate (SAR) below worldwide limits). However, the assessment of SAR does not provide information on the mechanisms of interaction between low-intensity electromagnetic fields emitted by wearable antennas and the human body. In this paper, we presented a detailed investigation of the SAR induced in erythrocyte suspensions from a fully textile wearable antenna at realistic (net input power 6.3 mW) and conservative (net input power 450 mW) conditions at 2.41 GHz, as well as results from in vitro experiments on the stability of human erythrocyte membranes at both exposure conditions. The detailed investigation showed that the 1 g average SARs were 0.5758 W/kg and 41.13 W/kg, respectively. Results from the in vitro experiments demonstrated that the short-term (20 min) irradiation of erythrocyte membranes in the reactive near-field of the wearable antenna at 6.3 mW input power had a stabilizing effect. Long-term exposure (120 min) had a destabilizing effect on the erythrocyte membrane.
The morphostructural features of the Lilyak Plateau and it’s spatial and morphotectonic relationships with the adjacent parts of the Eastern Pre-Balkan Mountains are examined in the light of modern mobilist ideas. The Lilyak Plateau landform is part of the South Moesian morphostructural zone. This morphostructure borders distinctly to the south with the northern border of the corresponding part of the Fore Hemus morphostructural zone. There are significant morphostructural and morphotectonic differences between these two regional morphostructural units.
In recent years, the interest in the Internet of Things (IoT) has been growing because this technology bridges the gap between the physical and virtual world, by connecting different objects and people through communication networks, in order to improve the quality of life. New IoT wearable devices require new types of antennas with unique shapes, made on unconventional substrates, which can be unobtrusively integrated into clothes and accessories. In this paper, we propose a fully textile dual-band logo antenna integrated with a reflector for application in IoT wearable devices. The proposed antenna’s radiating elements have been shaped to mimic the logo of South-West University “Neofit Rilski” for an unobtrusive integration in accessories. A reflector has been mounted on the opposite side of the textile substrate to reduce the radiation from the wearable antenna and improve its robustness against the loading effect from nearby objects. Two antenna prototypes were fabricated and tested in free space as well as on three different objects (human body, notebook, and laptop). Moreover, in the two frequency ranges of interest a radiation efficiency of 25–38% and 62–90% was achieved. Moreover, due to the reflector, the maximum local specific-absorption rate, which averaged over 10 g mass in the human-body phantom, was found to be equal to 0.5182 W/kg at 2.4 GHz and 0.16379 W/kg at 5.47 GHz. Additionally, the results from the performed measurement-campaign collecting received the signal-strength indicator and packet loss for an off-body scenario in real-world use, demonstrating that the backpack-integrated antenna prototype can form high-quality off-body communication channels.
Snezhnika and Banski Suhodol glacierets in the Pirin Mountains are the southernmost surface ice accumulations in Europe. Apart from direct snowfall, substantial inputs from avalanching feed both glacierets. Both glacierets appear to be more stable than any other small glacier in the Mediterranean region. Although accurate knowledge of ice thickness distribution and bedrock topography is essential to understand the long-term dynamics of these ice bodies, such data are lacking for the Balkan Peninsula glaciers. Detailed GPR measurements conducted in 2018 using a 100 MHz frequency antenna revealed a maximum thickness of 17 m at Banski Suhodol and 12 m at Snezhnika. Two distinct main layers revealed by density variations were inferred at Snezhnika and several clear internal reflections observed on the radargrams were associated with thin debris layers. Based on the morphological evidence of the former ice extents and high-resolution digital elevation models, 3D reconstructions of ice thickness distribution during the Little Ice Age (LIA) were generated. The results revealed that since LIA the volume of Snezhnika dropped by 123%, and that of Banski Suhodol by 83%. Both glacierets reached maximum thickness values 5 m greater than the present ones during LIA. For the first time, ERT measurements and miniature thermistors were used to investigate ground ice occurrence in the vicinity of the Pirin's glacierets. The ERT measurements revealed no glacial ice in the proglacial area of Banski Suhodol nor in the frontal moraine. Ice-rich frozen debris and frozen sediments without massive ice occur downslope the glacieret on a slope covered by loose rock deposits. Based on the ground surface thermal data, permafrost appears likely on this scree slope, where persistent or late lying snow cover occurs regularly. Our investigation revealed that permafrost is not necessarily related to rock glaciers occurrence in the Balkan Peninsula.
Poisoning is one of the biggest threats to vultures worldwide. It has mainly been used illegally to control the populations of wild predators but as an indirect consequence, vultures have been severely affected. After consuming poison bait vultures can travel a considerable distance before dying. As a result, dead birds found cannot be linked to the poisoned bait, and often even the bait remains undetected. Here we report on the poisoning of two GPS-tracked Griffon Vultures and present valuable data in the context of forensic considerations related to wildlife crime cases investigation. Proper analysis of GPS data in a real-time and quick finding of the poisoned bait is key for preventing further poisoning. The present study provides insight into the mechanics of poisoning of vultures and other bird species. It also indicates that the use of high-resolution GPS transmitters may be the only possible way to find the exact location of the poisoned bait and to relate away-dying birds with it.
The aim of the author is to analyse the legal restrictions provided by the Treaty on the Functioning of the European Union on the free movement of capital to or from third countries. Those restrictions are reviewed in terms of the reasons upholding them, the objectives pursued by them and the hypotheses in which they are applicable. Practical examples are given, and relevant case law of the Court of Justice of the European Union is presented.
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385 members
Elena Stavrova
  • Department of Finance and Accounting
Ivan Krumov Todorov
  • Department of Finance and Accounting
Tatyana A. Dzimbova
  • Department of Anatomy and Physiology
Velin Kralev
  • Department of Informatics
Maya Georgieva Chochkova
  • Department of Chemistry
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