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Photometric observations and light curve solutions of the W UMa stars NSVS 2244206,NSVS 908513,CSS J004004.7+385531 and VSX J062624.4+570907

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Research in Astronomy and Astrophysics 2016年第9期16卷 15-22页

作者： diana petrova Kiurkchieva Velimir Angelov Popov Doroteya Lyubenova Vasileva Nikola Ivanov Petrov Department of Physics Shumen University115Universitetska Str.1712 ShumenBulgaria IRIDA Observatory 17A Prof.Asen Zlatarov Str.SofiaBulgaria Institute of Astronomy and National Astronomical Observatory Bulgarian Academy of Sciences72Tsarigradsko Shose Blvd.1784 SofiaBulgaria

Photometric observations in Sloan 9＇ and i＇ bands of four W UMa stars, NSVS 2244206, NSVS 908513, CSS J004004.7＋385531 and VSX J062624.4＋570907, are presented. The light curve solutions reveal that all targets have overcontact configurations with fillout factors within 0.15-0.26. Their components are G-K spectral types and are almost in thermal contact. They are also relatively close in size and luminosity： the radius ratios r2/r1 are within 0.75-0.90; the luminosity ratios 12/11 are within 0.53-0.63. The results of the light curve solution of CSS J004004.7＋385531 imply the weak limb-darkening effect of its primary component and possible presence of additional absorbing features in the system.

关键词： methods data analysis -- stars fundamental parameters -- stars binaries eclipsing individ-ual (NSVS 2244206, NSVS 908513, CSS J004004.7+385531, VSX J062624.4+570907)

Observations and light curve solutions of the W UMa binaries V796 Cep,V797 Cep,CSS J015341.9+381641 and NSVS 3853195

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Research in Astronomy and Astrophysics 2017年第5期17卷 31-38页

作者： diana petrova Kjurkchieva Velimir Angelov Popov Sunay Ibryamov Ibryamov Doroteya Lyubenova Vasileva Nikola Ivanov Petrov Department of Physics Shumen University115 Universitetska Str.9712 ShumenBulgaria IRIDA Observatory Rozhen NAOBulgaria Institute of Astronomy and NAO Bulgarian Academy of Sciences72 Tsarigradsko Shose Blvd.1784 SofiaBulgaria

Photometric observations in Sloan g′and i′bands of four W UMa binaries, V796 Cep,V797 Cep, CSS J015341.9＋381641 and NSVS 3853195, are presented. Our observations showed that CSS J015404.1＋382805 and NSVS 3853195 are the same star. We determined the initial epochs T_0 of all targets and found improved values for the period of NSVS 3853195. The light curve solutions of our data revealed that the components of each target are almost the same in terms of mass, temperature,radius and luminosity. The stellar components are G and K spectral types and undergo partial *** systems have barely-overcontact configurations and can be classified as H subtype W UMa *** established that the relation between the luminosity ratio l_2/l_1 and mass ratio q of our targets is approximately l_2/l_1 = q^（1.5）.

关键词： stars: binaries: eclipsing -- stars: fundamental parameters -- stars: individual (V796 Cep,V797 Cep CSS J015341.9+381641 NSVS 3853195)

Telbivudine vs tenofovir in hepatitis B e antigen-negative chronic hepatitis B patients: OPTIMA roadmap study

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World Journal of Hepatology 2016年第32期8卷 1402-1413页

作者： Zahari Krastev diana petrova Iskren Kotzev Mustafa Kemal Celen Meryl Mendelson Richa Chandra Priti Pandey Kamal Hamed Clinic of Gastroenterology St.Ivan Rilsky University HospitalMedical University Department of Gastroenterology University Hospital Alexandrovska Clinic of Hepatogastroenterology University Hospital St Marina Infectious Disease Clinic Dicle University Novartis Pharmaceuticals Corporation East Hanover Novartis Healthcare Pvt. Ltd.

AIMTo make efficacy and safety comparison of telbivudine-raodmap and tenofovir-roadmap in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB) patients. METHODSThis was the first prospective, randomised, two-arm, open-label, non-inferiority study in HBeAg-negative CHB patients that compared telbivudine and tenofovir administered as per roadmap concept. Patients were treated up to 24 wk and, depending on virologic response, continued the same therapy or received add-on therapy up to 104 wk. Eligible patients received an additional 52 wk of treatment in the extension period (i.e., up to 156 wk). Patients who developed virologic breakthrough (VB) while on monotherapy also received add-on therapy. The primary efficacy endpoint was the rate of patients achieving hepatitis B virus (HBV) DNA RESULTSA total of 241 patients were randomised. Non-inferiority of telbivudine arm to tenofovir arm was demonstrated at week 52 (± 7 d window), with over 91% of patients in each treatment arm achieving HBV DNA level CONCLUSIONEfficacy was shown for both telbivudine-roadmap and tenofovir-roadmap regimens in HBeAg-negative CHB patients over 156 wk. Telbivudine arm was associated with renal improvement.

关键词： Chronic hepatitis B Glomerular filtration rate Telbivudine Tenofovir Roadmap concept

Chronic hepatitis C virus infection:Prevalence of extrahepatic manifestations and association with cryoglobulinemia in Bulgarian patients

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World Journal of Gastroenterology 2007年第48期13卷 6518-6528页

作者： diana V Stefanova-petrova Anelia H Tzvetanska Elisaveta J Naumova Anastasia P Mihailova Evgenii A Hadjiev Rumiana P Dikova Mircho I Vukov Konstantin G Tchernev Department of Internal Diseases and Gastroenterology University Hospital Alexandrovska Viral Laboratory University Pediatric Hospital Central Laboratory of Immunology University Hospital Alexandrovska Department of Hematology University Hospital Alexandrovska Department of Pathology University Hospital Alexandrovka National Centre for Health Information

AIM: To assess the prevalence of extrahepatic manifestations in Bulgarian patients with chronic hepatitis C virus (HCV) infection and identify the clinical and biological manifestations associated with cryoglobulinemia. METHODS: The medical records of 136 chronically infected HCV patients were reviewed to assess the prevalence of extrahepatic manifestations. Association between cryoglobulin-positivity and other manifestations were identified using χ2 and Fisher’s exact test. Risk factors for the presence of extrahepatic manifestations were assessed by logistic regression analysis. RESULTS: Seventy six percent (104/136) of the patients had at least one extrahepatic manifestation. Clinical manifestations included fatigue (59.6%), kidney impairment (25.0%), type 2 diabetes (22.8%), paresthesia (19.9%), arthralgia (18.4%), palpable purpura (17.6%), lymphadenopathy (16.2%), pulmonary fi brosis (15.4%), thyroid dysfunction (14.7%), Raynaud’s phenomenon (11.8%), B-cell lymphoma (8.8%), sicca syndrome (6.6%), and lichen planus (5.9%). The biological manifestations included cryoglobulinproduction (37.5%), thrombocytopenia (31.6%), and autoantibodies: anti-nuclear (18.4%), anti-smooth muscle (16.9%), anti-neutrophil cytoplasm (13.2%) and anti-cardiolipin (8.8%). All extrahepatic manifestations showed an association with cryoglobulin-positivity, with the exception of thyroid dysfunction, sicca syndrome, and lichen planus. Risks factors for the presence of extrahepatic manifestations (univariate analysis) were: age ≥ 60 years, female gender, virus transmission by blood transfusions, longstanding infection (≥ 20 years), and extensive liver fi brosis. The most signifi cant risks factors (multivariate analysis) were longstanding infection and extensive liver fi brosis. CONCLUSION: We observed a high prevalence of extrahepatic manifestations in patients with chronic HCV infection. Most of these manifestations were associated with impaired lymphoproliferation and cryoglobulin produc

关键词： Hepatitis C Liver cirrhosis Extrahepatic manifestations

Detection of Malignant and Benign Breast Cancer Using the ANOVA-BOOTSTRAP-SVM

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Journal of Data and Information Science 2020年第2期5卷 62-75页

作者： Borislava petrova Vrigazova Department of Statistics and Econometric Faculty of Economics and Business AdministrationSofia UniversityBulgaria

Purpose:The aim of this research is to propose a modification of the ANOVA-SVM method that can increase accuracy when detecting benign and malignant breast ***:We proposed a new method *** involves applying the analysis of variance(ANOVA)to support vector machines(SVM)but we use the bootstrap instead of cross validation as a train/test splitting *** have tuned the kernel and the C parameter and tested our algorithm on a set of breast cancer ***:By using the new method proposed,we succeeded in improving accuracy ranging from 4.5 percentage points to 8 percentage points depending on the *** limitations:The algorithm is sensitive to the type of kernel and value of the optimization parameter *** implications:We believe that the ANOVA-BOOTSTRAP-SVM can be used not only to recognize the type of breast cancer but also for broader research in all types of ***/value:Our findings are important as the algorithm can detect various types of cancer with higher accuracy compared to standard versions of the Support Vector Machines.

关键词： Breast cancer detection ANOVA Bootstrap Support vector machines

Chronic Epstein-Barr virus-related hepatitis in immunocompetent patients

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World Journal of Gastroenterology 2006年第35期12卷 5711-5716页

作者： Mihaela petrova Maria Muhtarova Maria Nikolova Svetoslav Magaev Hristo Taskov diana Nikolovska Zahariy Krastev Clinic of Gastroenterology Medical Institute Ministry of Interior Sofia Bulgaria Central Laboratory of Immunology National Centre of Infectious and Parasitic Diseases Sofia Bulgaria Clinic of Gastroenterology University Hopsital "St. Iv. Rilsky" Sofia BulgariaCo-first-author: Maria Muhtarova

AIM: To investigate reactivated Epstein-Barr virus (EBV) infection as a cause for chronic hepatitis. METHODS: Patients with occasionally established elevated serum aminotransferases were studied. HIV, HBV and HCV-infections were excluded as well as any other immunosuppressive factors, metabolic or toxic disorders. EBV viral capsid antigen (VCA) IgG and IgM, EA-R and EA-D IgG and Epstein-Barr nuclear antigen (EBNA) were measured using IFA kits. Immunophenotyping of whole blood was performed by multicolor flow cytometry. CD8+ T cell responses to EBV and PHA were determined according to the intracellular expression of IFN-γ. RESULTS: The mean alanine aminotransferase (ALT) and gamma glutamyl transpeptidase (GGTP) values exceeded twice the upper normal limit, AST/ALT ratio < 1. Serology tests showed reactivated EBV infection in all patients. Absolute number and percentages of T, B and NK cells were within the reference ranges. Fine subset analysis, in comparison to EBV+ healthy carriers, revealed a significant decrease of naive T cells (P < 0.001), accompanied by increased percentage of CD45RA- (P < 0.0001), and terminally differentiated CD28-CD27- CD8+ T cells (P < 0.01). Moderately elevated numbers of CD38 molecules on CD8+ T cells (P < 0.05) proposed a low viral burden. A significantly increased percentage of CD8+ T cells expressing IFN-γ in response to EBV and PHA stimulation was registered in patients, as compared to controls (P < 0.05). Liver biopsy specimens from 5 patients revealed nonspecific features of low-grade ***: Chronic hepatitis might be a manifestation of chronic EBV infection in the lack of detectable immune deficiency; the expansion of CD28- CD27- and increase of functional EBV-specific CD8+ T cells being the only surrogate markers of viral activity.

关键词： Chronic hepatitis Epstein-Barr Epstein-Barr virus-specific CD8+ T cell

Same Eastern Europe,Different Attitudes towards China——The Differences between the Foreign Policies of Bulgaria and Poland towards China after 1989

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Same Eastern Europe,Different Attitudes towards China——The...

作者： Ivanova Zlatina petrova 华东师范大学

学位级别：硕士

2019年是中华人民共和国成立70周年。这也标志着中国与保加利亚、中国和波兰建交70周年。从建交时间上来看,保加利亚与波兰只有三天的差距,分别是1949年10月4日与1949年10月7日。彼时,两国正式承认中华人民共和国,并与这个新的国家实体... 详细信息

2019年是中华人民共和国成立70周年。这也标志着中国与保加利亚、中国和波兰建交70周年。从建交时间上来看,保加利亚与波兰只有三天的差距,分别是1949年10月4日与1949年10月7日。彼时,两国正式承认中华人民共和国,并与这个新的国家实体建立了外交关系。近70年来,中保关系和中波关系的发展虽然经历了一些紧张和困难的时期,但他们也不断地加强、改善两国之间的关系。因此,我们现在所拥有的是一个有着相对悠久历史的国家,我们所看到的和期待的对于中国和保加利亚,中国和波兰的双方关系来说,无疑是一个光明且充满希望的未来。这个研究致力于保加利亚和波兰对中国的外交政策。其目的是审视1989年后保加利亚和波兰对华外交政策之间的差异。理由是分析中保关系和中波关系以及保加利亚和波兰对中华人民共和国的态度。我认为保加利亚和波兰之间存在意识形态差异。保加利亚对中国更加务实和友好,而波兰因为更具意识形态性而对中国相对不那么友好。

关键词：中国保加利亚波兰外交政策

Synthesis and characterization of yttrium-aluminum-iron and yttrium-cerium-iron citric complexes

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Journal of Rare Earths 2008年第3期26卷 307-314页

作者： N. petrova D. Todorovsky1 I. Mitov G. Tyuliev Faculty of Chemistry University of Sofia 1 J. Bourchier Blvd. Sofia 1164 Bulgaria Institute of Catalysis Bulgarian Academy of Sciences Acad. G. Bonchev Str. bl. 11 Sofia 1113 Bulgaria

Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol （EG） medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR,^ 13C and ^1H NMR, X-ray photoelectron and Mossbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bonded as adduct and ester with citric acid ligand and did not contain ligands with deprotonated alcoholic groups. The complexes consisted of agglomerated spheres, 0.7-3 μm in diameter. The local composition of the products was established by energy dispersive X-ray microanalysis. The comparison of the number of the ligands, their average electrical charge and the esterification degree of mono-, di- and trimetallic complexes proved the mixed-metal nature of the species studied. The thermal decomposition of the complexes was studied and a general scheme of the processes taking place was proposed. Highly crystalline, phase homogeneous YaFe4AlO12 was produced after heating the respective complex at 1000 ℃. Ce-doped yttrium-iron garnet, similarly prepared, contained traces of CeO2.

关键词： garnets polymerized complex method Mossbauer spectroscopy thermal analysis NMR-spectroscopy rare earths

Structure-activity relationship in water-gas shift reaction over gold catalysts supported on Y-doped ceria

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Journal of Rare Earths 2019年第4期37卷 383-392页

作者： Tatyana Tabakova Lyuba Ilieva Ivan Ivanov Maela Manzoli Rodolfo Zanella Petya petrova Zbigniew Kaszkur Institute of Catalysis Bulgarian Academy of Sciences Department of Drug Science and Technology & Centre for Nanostructured Interfaces and Surfaces University of Turin Centro de Ciencias Aplicadas y Desarrollo Tecnologico Universidad Nacional Autonoma de Mexico Institute of Physical Chemistry PAS

The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(>90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y^(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.

关键词： Gold catalyst Water gas shift reaction Doped ceria Yttrium Hydrogen production Rare earths