24 research outputs found
Some Contribuitions of the Neo-Deterministic Seismic Hazard Assessment Approach to Earthquake Risk Assessment for the City of Sofia
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Generated Accelerograms on the Example of Sofia City for the Purposes of Microzonation
No full textExpected seismic excitation is analyzed along three profiles with length of 14 km, passing through the central part of Sofia city. Accelerograms are simulated for a scenario earthquakes with M=7. A hybrid modelling method is applied, based on the modal summation technique and finite differences scheme. The site amplification is calibrated taking into account the response spectra ratio of 2D to 1D models. As a result accelerograms are generated at intervals of 100 m along the three profiles. The seismic response of reinforced concrete industrial building designed according to the Eurocodes is studied by use of the generated accelerograms. Response characteristics, such as damage index and story drift are calculated. Maps of distribution of the damage index on the area covered by the three profiles are plotted for the considered scenario. The results could be used for the purpose of microzonation.JRC.DG.G.5 - European laboratory for structural assessmen
The BTC Price Prediction Paradox Through Methodological Pluralism
No full textBitcoin’s extreme price volatility presents significant challenges for investors and traders, necessitating accurate predictive models to guide decision-making in cryptocurrency markets. This study compares the performance of machine learning approaches for Bitcoin price prediction, specifically examining XGBoost gradient boosting, Long Short-Term Memory (LSTM), and GARCH-DL neural networks using comprehensive market data spanning December 2013 to May 2025. We employed extensive feature engineering incorporating technical indicators, applied multiple machine and deep learning models configurations including standalone and ensemble approaches, and utilized cross-validation techniques to assess model robustness. Based on the empirical results, the most significant practical implication is that traders and financial institutions should adopt a dual-model approach, deploying XGBoost for directional trading strategies and utilizing LSTM models for applications requiring precise magnitude predictions, due to their superior continuous forecasting performance. This research demonstrates that traditional technical indicators, particularly market capitalization and price extremes, remain highly predictive in algorithmic trading contexts, validating their continued integration into modern cryptocurrency prediction systems. For risk management applications, the attention-based LSTM’s superior risk-adjusted returns, combined with enhanced interpretability, make it particularly valuable for institutional portfolio optimization and regulatory compliance requirements. The findings suggest that ensemble methods offer balanced performance across multiple evaluation criteria, providing a robust foundation for production trading systems where consistent performance is more valuable than optimization for single metrics. These results enable practitioners to make evidence-based decisions about model selection based on their specific trading objectives, whether focused on directional accuracy for signal generation or precision of magnitude for risk assessment and portfolio management
D-dimer – laboratory aspects and clinical application
No full textD-димер е краен продукт на плазминовото разграждане на кръстосано-свързания фибрин и е маркер за активацията на коагулационната и фибринолитичната системи. В рутинната клинична практика се използва широко за изключване на венозен тромбоемболизъм (ВТЕ), за оценка на риска от рецидивиращи тромбози и определяне на оптималната продължителност на антикоагулантната терапия, за диагноза и мониториране на синдром на дисеминирана интравазална коагулация (ДИК). Аналитичните методи за измерване на D-димер се характеризират с висока чувствителност, но относително ниска специфичност, тъй като D-димер е повишен при редица физиологични и патологични състояния. Комбинацията от измерването на D-димер със скали за оценка на клиничната вероятност позволява безопасно отхвърляне на ВТЕ. С цел повишаване на диагностичната надеждност са предложени стратегии, които да повишат специфичността на D-димер. Прилагането на възрастово-коригиран и адаптиран към клиничната вероятност разграничителен праг за ВТЕ позволява отхвърляне на диагнозата при по-голям брой пациенти без да се налага извършване на допълнителни образни изследвания. D-dimer is a terminal product of plasmin-mediated degradation of cross-linked fibrin and is a marker for the activation of both the coagulation and fibrinolytic systems. D-dimer is widely used in routine clinical practice to rule out venous thromboembolism (VTE), assess the risk of recurrent thrombosis, and determine the optimal duration of anticoagulant therapy, as well as for the diagnosis and monitoring of disseminated intravascular coagulation (DIC). The analytical methods for measuring D-dimer are high sensitive but relatively low specific, as D-dimer levels are elevated in several physiological and pathological conditions. The combination of D-dimer measurements with clinical probability scores allows for the safe exclusion of VTE. To improve diagnostic accuracy, several strategies have been proposed to increase the specificity of D-dimer testing. The application of age-adjusted and clinical probability adapted cutoff values for VTE allows VTE exclusion in a greater number of patients without the need for additional imaging studies
Preliminary Results on October 27, 2004 Vrancea Earthquake - Case Study on Sofia Strong Ground
No full textThe intermediate-depth earthquakes in Vrancea (Romania) are particularly notable in the group of the European earthquakes. The scope of this work is to show preliminary results of the seismic effects of 27, October, 2004 earthquake from the Vrancea seismogenic zone. Particular attention is done on the records registered in Bucharest and Sofia. The study is limited to the question about the level of the ground motions in terms of recorded spectral amplitudes during 2004 Vrancea strong earthquakes. For this purpose we discuss: (1) the strong ground motion records in due to Vrancea strong earthquake, 2004; (2) the regional seismicity and a review of the available recurrence and attenuation relationships; (3) results from the response of one storey building due to scaled record in Sofia.
The results of this study confirm the significant influence of the Vrancea intermediate-depth seismogenic zone on very large territory of Bulgaria and the need to provide realistic seismic input, from Vrancea sources, for the purposes of seismic microzonation.JRC.G.5 - European laboratory for structural assessmen
Antiplatelet therapy – platelet function test for platelet response assessment
No full textДвойната антиагрегантна терапия е основен фармакологичен механизъм за потискане на тромбоцитната функция с цел предотвратяване на тромботичните усложнения след перкутанна коронарна ангиопластика. Настоящите проучвания показват, че използването на прецизирана антитромбоцитна терапия води до значимо клинично подобрение след имплантация на стент. Необходимостта от индивидуализиране на терапията се обуславя от наличието на широки интериндивидуални вариации в тромбоцитния отговор и от различната фармакодинамика на отделните P2Y12 инхибитори – клопидогрел, празугрел и тикагрелор. Оценката на ADP индуцираната тромбоцитната агрегация спомага за предотвратяване както на нежеланите исхемични събития, така и на асоциирания риск от кървене. Основната цел на нашите проучвания първоначално беше установяване и преодоляване на резистентността към терапията с клопидогрел с оглед намаляване на нежеланите исхемични събития. С прилагането на празугрела и тикагрелора – медикаментите с по-силен и предвидим антиагрегантен ефект, вниманието ни се насочи към установяване на увеличен отговор и кървене на фона на двойна антиагрегантна терапия и индивидуализирането ѝ, с цел минимизиране на кървенето. Дългогодишният ни опит показва, че импедансната агрегометрия е бърз и надежден метод за оценка на тромбоцитната функция. Тестовете дават възможност за диференциране на пациентите с оптимална, висока и ниска тромбоцитна реактивност към терапията с P2Y12 инхибитори. Основният извод от нашите проучвания – липсата на исхемични събития при индивидуализирането на терапията без увеличаване на хеморагичния риск, осигурява намирането на баланс между исхемичните и хеморагичните усложнения по време на терапия. Dual antiplatelet therapy is the main pharmacological mechanism used to suppress platelet function in order to prevent thrombotic complications following percutaneous coronary angioplasty. Current studies show that the use of tailored antiplatelet therapy leads to significant clinical improvement after stent implantation. The need to individualize therapy is due to the presence of wide interindividual variations in platelet response and the differing pharmacodynamics of various P2Y12 inhibitors – clopidogrel, prasugrel, and ticagrelor. Assessment of ADP-induced platelet aggregation helps prevent both adverse ischemic events and the associated bleeding risk. The primary objective of our studies was initially to establish and overcome resistance to clopidogrel therapy with the aim of reducing adverse ischemic events. With the introduction of prasugrel and ticagrelor – medications that offer a stronger and more predictable antiplatelet effect – our focus shifted to identifying increased response and bleeding in the context of dual antiplatelet therapy, and to individualizing therapy to minimize bleeding. Our long-term experience shows that impedance aggregometry is a fast and reliable method for evaluating platelet function. The tests allow for the differentiation of patients with optimal, high, and low platelet reactivity to P2Y12 inhibitor therapy. The main conclusion from our studies is that individualizing therapy leads to the absence of ischemic events without an increased risk of hemorrhage, thereby achieving a balance between ischemic and hemorrhagic complications during treatment
Knowledge Clusters – A Tendency for Achieving Competitive Advantage
No full textThis paper initiates the start of a research process of knowledge clusters definition, main prerequisites for their establishment, formation stages and key participants. It presents one example of a knowledge cluster in Spain, by describing its establishment process, main participants and mechanisms of functioning. The author describes some of the projects and initiatives in the field of knowledge cluster formations in Bulgaria. On the base of the literature review and the Bulgarian experience in that area, some conclusions are drawn. The author states that this article raises more questions than giving certain answers. It also reveals a broad arena for future research work.</p
Prenatal Renal Vein Thrombosis
No full textBackground: The neonatal period has a number of characteristics leading to an increased risk of severe and, in many cases, life-threatening complications. Renal venous thrombosis is one of them. It accounts for 16–20% of all thromboembolisms in the neonatal period. Due to the delicate balance in coagulation status in the first days after birth, conditions such as infections, hypoxia, hypotension, and dehydration can lead to the occurrence of this complication. The incidence of renal thrombosis is 2.2/100,000 live births, with cases of intrauterine renal thrombosis being even rarer (7% of cases). The diagnosis of the disease is usually performed using ultrasound examination and Doppler sonography, although contrast angiography is the gold standard for diagnosing these conditions. Case presentation: We present a clinical case of a male child with manifestations of diabetic fetopathy and prenatally occurring venous thrombosis of the right kidney, confirmed by ultrasound 2 h after birth. Results: The occurrence and evolution of venous thrombosis was monitored through a series of ultrasound examinations. Despite the restoration of renal blood flow after the initiation of therapy, long-term follow-up at 6 and 12 months revealed the onset of renal atrophy. Conclusions: Prenatal renal vein thrombosis is a rare but severe pathology for the newborns. Ultrasound examination is the method of first choice in cases of suspected renal vein thrombosis, as well as for renal blood flow restoration and for the monitoring of the fate of the affected kidney
From Communism to Capitalism: The Transition of Bulgarian Tourism Sector and Contemporary Discourses
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