Photoluminescence of Neutron-Irradiated LiF Single Crystals
In 1980, a single LiF crystal was irradiated by thermal neutrons up to the exposition dose 1019 n/cm2 at the Salaspils nuclear reactor. The crystal has been kept at room temperature for 29 years. Samples in size of 5×4×1 mm3 were cut from the crystal and some of them annealed at 920 K for 30 min. To study photoluminescence, measurements with a confocal laser scanning microscope Leica TCS SP5 were performed, during which 3D-defects of size of ~1μm3 were revealed. Photoluminescence was observed in the red spectral region with the peak of ~ 655 nm when excited with an argon laser (Δ = 458 nm).
The installation of thermal energy storage system (TES) provides the optimisation of energy source, energy security supply, power plant operation and energy production flexibility. The aim of the present research is to evaluate the feasibility of thermal energy system installation at Riga TPP–2. The six modes were investigated: four for non-heating periods and two for heating periods. Different research methods were used: data statistic processing, data analysis, analogy, forecasting, financial method and correlation and regression method. In the end, the best mode was chosen – the increase of cogeneration unit efficiency during the summer.
Festuca L. is one of the most complicated genera in Poaceae. Polyacrylamide gel electrophoresis was used to study the isoenzyme variation of glutamate-oxaloacetate transaminase, malate dehydrogenase, glutamate dehydrogenase, isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase in natural populations of F. valesiaca Schleich. ex Gaud., F. rupicola Heuff., F. dalmatica (Hack.) K. Richt. and F. stojanovii (Acht.) Kozuharov ex Foggi & Petrova. The aim of the present study was to assess isoenzyme variation and genetic affinities among the four species of the genus Festuca. Genetic identities (I) and distances (D) were calculated to evaluate qualitative genetic affinities and systematic relationships among the species. Considering the patterns of isoenzyme variation in the studied group, it is evident that F. dalmatica and F. stojanovii are closely related species. The species F. valesiaca and F. rupicola are isoenzymatically well characterized as distinct genetic entities. The obtained results generally support recent narrow species concept in the genus Festuca.
A. Ivanova, A. Tokmakov, K. Lebedeva, M. Roze and I. Kaulachs
Organometal halide perovskites are promising materials for lowcost, high-efficiency solar cells. The method of perovskite layer deposition and the interfacial layers play an important role in determining the efficiency of perovskite solar cells (PSCs). In the paper, we demonstrate inverted planar perovskite solar cells where perovskite layers are deposited by two-step modified interdiffusion and one-step methods. We also demonstrate how PSC parameters change by doping of charge transport layers (CTL). We used dimethylsupoxide (DMSO) as dopant for the hole transport layer (PEDOT:PSS) but for the electron transport layer [6,6]-phenyl C61 butyric acid methyl ester (PCBM)) we used N,N-dimethyl-N-octadecyl(3-aminopropyl)trimethoxysilyl chloride (DMOAP).
The highest main PSC parameters (PCE, EQE, VOC) were obtained for cells prepared by the one-step method with fast crystallization and doped CTLs but higher fill factor (FF) and shunt resistance (Rsh) values were obtained for cells prepared by the two-step method with undoped CTLs.
I. Dimitrova Ivanova, B. Atanasova, S. Dragneva, L. Vladimirova, Z. Krastev, A. Kostadinova, A. Ivanova and K. Tzatchev
Pre-analytical factors of variation need to be carefully considered and investigated in efforts to harmonize all aspects of the total testing process. This study aimed to evaluate contamination and stability in copper (Cu) analysis of serum and urine by flame atomic absorption spectroscopy (FAAS) and to compare the stability of urine Cu in controls and in D-penicillamine (D-PA) administration. Cu was measured by AAnalyst 400, Perkin Elmer, USA. Blood was collected in BD Vacutainer®SSTTM II Advance tubes and BD Vacutainer® Trace Element tubes. Sterile polyethylene and polypropylene vessels for collection, transportation, storage and preliminary preparation of samples were used in urinalysis. Stability in serum and 24 h urine was evaluated in two temperature regimens: 15-25°C and 2-8°C, for particular time of storage. No significant differences (p = 0.20) in Cu concentration was found between the two types of tested tubes with patient`s sera. The stability of the samples (serum and urine) was better at refrigeration temperature. In urine the stability was better in D-PA administration.Standardization of Cu analysis could be achieved by assessing the aspects of pre-analytical factors of variations.
Albena Merdzhanova, Veselina Panayotova, Diana A. Dobreva, Rostitsa Stancheva and Katya Peycheva
Rapana venosa is an edible mollusc with nutritional and economic importance. There is limited information about its lipid composition. The aim of the present study is to provide information about lipid composition, fatty acid profiles, fat soluble vitamins and cholesterol content of raw and cooked Rapana venosa. Cooking did not affect the ratio of lipid classes, but fatty acids composition varied significantly. Considerable variations were observed in fatty acid distribution of total lipids and neutral lipids. Fatty acid groups of phospholipids remained unaffected by temperature treatment. The most abundant fatty acids in all lipid classes of raw and cooked specimens were palmitic acid (C16:0) and eicosapentaenoic acid (C20:5n-3). The sum of omega-3 polyunsaturated fatty acids (PUFA) was higher than omega-6 PUFA in all lipid fractions. The results of the present study showed that cooking process affected cholesterol, fat soluble vitamins and carotenoids content differently. Larger variations were observed for vitamin A, β-carotene and astaxanthin and to lesser for vitamin E. Cholesterol and vitamin D3 were also affected by the thermal stress. The present study revealed that Rapana venosa meat could be a good source of high quality nutritional lipids, which are well preserved even after culinary treatment
I. Ivanova, B. Atanasova, A. Kostadinova, Y. Bocheva and K. Tzatchev
Copper (Cu) and zinc (Zn) are essential for life. Body Cu and Zn content depends on variety of factors - age, gender, and diet, type of drinking water, geographical location and genetic predisposition. Copper status becomes even more relevant not only in rare genetic disorders such as Wilson disease but in diseases such as cardiovascular ones, impaired glucose tolerance and neuro-degenerative and tumor diseases. The study aimed to examine the distribution of serum Cu and Zn in a representative group of the Bulgarian population and to describe factors which influence metal content. It also aimed to describe the link between serum Cu levels and the frequency of Alzheimer’s disease (AD) in Bulgarians. Cu and Zn in serum were measured in 379 individuals (172 males and 207 females) from 5 different regions in Bulgaria by flame atomic absorption using AAnalyst 400, Perkin Elmer. Statistical analyses were performed by SPSS, 19. Median and inert-quartile range (IQR) for blood Cu were 15.89 (13.87-7.89) μmol/L and for Zn - 13.00 (11.7-14.68) μmol/L in the examined group. Higher Cu levels in females than in males were found (p < 0.001). Decrease of Zn with aging was established (p > 0.05). Significant difference (p < 0.05) was found in serum Cu between young people (< 30 year old) and adults over 61 year old. Statistically significant difference in Cu and Zn was observed (p < 0.05) in respect of residences. Difference without significance was measured between serum lipids and serum Cu (p = 0.541) and Zn (p = 0.741).
I. Valkov, R. Ivanova, C. Marinova, A. Alexiev, K. Antonov, D. Jelev, R. S. Ivanova and L. Mateva
Serum lipids abnormalities are widespread among patients with chronic hepatitis C (CHC), but the impact of concomitant hepatic steatosis [steatosis, nonalcoholic steatosis (NAS)], as well as distinctions between it and nonalcoholic fatty liver disease (NAFLD) are not well established yet. The aim of the study was to assess and compare the serum lipids in patients with genotype 1 CHC with and without steatosis, those with NAFLD, and healthy controls (HC). A total of 1010 subjects were included in this study: 366 CHC genotype 1 patients with steatosis (n = 227) and without steatosis (n = 139), 403 NAFLD patients, and 241 HC without fatty liver or other disease, matched for age and gender. Serum lipids, body mass index (BMI), components of metabolic syndrome (MS), and serum insulin levels were evaluated. In addition serum lipoprotein (a) [Lp(a)] levels were studied in 112 CHC and 80 NAFLD patients. The mean levels of total cholesterol, LDL-cholesterol and triglycerides (Tg) were higher and the mean levels of HDL-cholesterol were lower in all patients with steatosis (CHC and NAFLD) than in CHC cases without steatosis (p < 0.05 and p = 0.001, resp.). Higher prevalence and severity of lipid abnormalities, including Lp(a), were observed in patients with NAFLD than in those with CHC (p < 0.001). No difference was found between CHC patients without steatosis and HC. Higher prevalence and grade of glucose metabolic abnormalities were also observed in patients with NAFLD and CHC with steatosis than in cases without steatosis (p < 0.05 and p = 0.001, resp.). Lipid and glucose metabolic abnormalities in patients with CHC were dependent on steatosis. CHC with steatosis and NAFLD were associated with insulin resistant type dyslipidemia, with total cholesterol and LDL-cholesterol being generally lower in CHC.
Michał A. Janiak, Adriana Slavova-Kazakova, Vessela D. Kancheva, Milena Ivanova, Tsvetelin Tsrunchev and Magdalena Karamać
The presented study revealed that there were changes in the phenolic compounds profile of extract of wild thyme (Thymus serpyllum L.) after γ-irradiation at the dose of 5 kGy. Ethanolic extracts of irradiated and non-irradiated herb were prepared and their compounds were analyzed by RP-HPLC-DAD technique. Between thirty two detected constituents, twelve phenolic compounds classified as hydroxybenzoic and hydroxycinnamic acids derivatives, flavones and flavanones were identified. Among them, caffeic acid derivatives and flavones predominated with the highest content of rosmarinic acid and luteolin-7-O-glucoside, respectively. Additionally, thymol was recognized in the analyzed extracts. γ-Irradiation slightly affected the quantitative profile of phenolic compounds of a wild thyme ethanolic extract. Only four constituents differed significantly (P<0.05) in terms of their content in the irradiated and non-irradiated samples. The content of phenolic acids (p-coumaric and caffeic acids) decreased and that of flavonoid aglycons (luteolin and eriodictyol) increased after the γ-ray treatment.
Oleg V. Borodin, Mikhail A. Bykov and Anna O. Ivanova
The height of a face in a 3-polytope is the maximum degree of its incident vertices, and the height of a 3-polytope, h, is the minimum height of its faces. A face is pyramidal if it is either a 4-face incident with three 3-vertices, or a 3-face incident with two vertices of degree at most 4. If pyramidal faces are allowed, then h can be arbitrarily large, so we assume the absence of pyramidal faces in what follows.
In 1940, Lebesgue proved that every quadrangulated 3-polytope has h ≤ 11. In 1995, this bound was lowered by Avgustinovich and Borodin to 10. Recently, Borodin and Ivanova improved it to the sharp bound 8.
For plane triangulation without 4-vertices, Borodin (1992), confirming the Kotzig conjecture of 1979, proved that h ≤ 20, which bound is sharp. Later, Borodin (1998) proved that h ≤ 20 for all triangulated 3-polytopes. In 1996, Horňák and Jendrol’ proved for arbitrarily polytopes that h ≤ 23. Recently, Borodin and Ivanova obtained the sharp bounds 10 for trianglefree polytopes and 20 for arbitrary polytopes.
In this paper we prove that any polytope has a face of degree at most 10 with height at most 20, where 10 and 20 are sharp.