Proceedings of the Bulgarian Academy of Sciences 2022-10-30T11:58:44+02:00 Ralitsa Boteva Open Journal Systems <p>Founded in 1948 by academician Georgy Nadjakov, "Comptes rendus de l’Académie bulgare des Sciences" is also known as "Доклади на БАН","Доклады Болгарской академии наук" and "Proceedings of the Bulgarian Academy of Sciences".</p> <p>If applicable, the name of the journal should be abbreviated as follows: C. R. Acad. Bulg. Sci. (according to ISO.)</p> <p><big><strong>Related subjects:</strong></big></p> <p class="condensed">Astronomy, Mathematics, Physics, Chemistry, Biology, Geology, Geophysics, Space Sciences, Engineering Sciences, Physical Geography, Medicine, Agricultural Sciences.</p> <p class="condensed">The manuscripts should contain only unpublished data in the respective scientific field. They can further be expanded to be published elsewhere. All manuscripts are subject to peer review and copy editing.</p> <p><strong><big>2002-2021 website:</big></strong></p> <p>The site with the archive of <em>Comptes rendus de l’Académie bulgare des Sciences</em> - 2002 to 2021 is <a href="" target="_blank" rel="noopener">still accessible at that address.</a></p> Some Notes on the Four-parameter Kies Distribution 2022-10-27T15:51:16+03:00 Tsvetelin Zaevski Nikolay Kyurkchiev <p>This short note is inspired by the work of [<sup>1</sup>] which is devoted on the four-parameter Kies distribution. Some of the results presented in this seminal paper need to be clarified. We present and prove the correct results following the original work.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Nullity Condition on Trans-Sasakian 3-Manifolds 2022-10-27T15:59:08+03:00 Wenjie Wang <p>In this paper, we are concerned with the κ-nullity condition on trans-Sasakian manifolds of dimension three. Such manifolds are classified under an additional assumption that the scalar curvature is invariant along the Reeb flow or a topology restriction.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Large Scale Ranking Using Stochastic Gradient Descent 2022-10-27T16:14:12+03:00 Engin Tas <p>A system of linear equations can represent any ranking problem that minimizes a pairwise ranking loss. We utilize a fast version of gradient descent algorithm with a near-optimal learning rate and momentum factor to solve this linear equations system iteratively. Tikhonov regularization is also integrated into this framework to avoid overfitting problems where we have very large and high dimensional but sparse data. </p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Bending Elasticity of Phospholipid Bilayers Containing an Amphipathic Peptide with Low Mammalian Cytotoxicity 2022-10-29T11:46:46+03:00 Victoria Vitkova Angelina Stoyanova-Ivanova Sirine Jaber Emilia Naydenova Dancho Danalev <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>Peptide mimetics imitate natural peptides’ structure but they could be specifically designed to be more selective concerning their toxicity to mammalian cells. In most cases this specificity is due to their ability to form α-helix in amphipathic environment. In addition, the specific activity depends on the ability of final structure to penetrate cell membrane. Being responsible for the cell integrity and compartmentalization, biomembranes also play a major role in cellular processes, in which the membrane deformations are important. In the present study we probe peptide-membrane interactions for a shortened amino acid sequence KLAKLAK-NH<sub>2</sub> of an antimicrobial peptide with apoptotic effect. The bending rigidity of model lipid bilayers is measured by flicker spectroscopy of quasispherical unilamellar vesicles monitored and analyzed in phase contrast light microscopy. At high peptide concentrations ∼ 30 μmol/L and peptide-to-lipid total molar ratios ∼ 0.90 bilayer stacking formation is observed. A reduction of the bending constant is reported at peptide-to-lipid total molar ratio ∼ 0.80. The membrane softening indicates peripheral peptide orientation at the lipid bilayer, which is considered a prerequisite for channel formation. Based on KLAKLAK-NH<sub>2</sub> effect on the membrane bending elasticity we provide an evaluation of the peptide partition coefficient characterizing its affinity to POPC bilayers. The acquired results might be helpful in efforts to further tailor the pharmacokinetic properties of antimicrobial peptides in combination with strengthened stability towards enzymatic degradation.</p> </div> </div> </div> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Comparative Study of Drought Tolerance of Virginia Tobacco Genotypes Differing in Origin and Their Corresponding Hybrid Progenies 2022-10-29T19:20:34+03:00 Elena Shopova Bistra Mihailova Marina Drumeva-Yoncheva Dessislava Todorova Iskren Sergiev Yonko Yonchev <p class="p1">Soil drought is a serious problem in agriculture leading to considerable loss of production. Tobacco is relatively sensitive to water scarcity, and the selection of resistant drought varieties is of particular importance. In this study we compared the tolerance to three different levels of drought of six genotypes of Virginia tobacco – two varieties were introduced in Bulgaria, two lines are of Bulgarian origin, and two are their hybrids. Biochemical markers of stress (malondialdehyde, hydrogen peroxide and free proline) were determined. The results showed that the Polish genotype V 385 and one of the Bulgarian lines L 0842 were moderately sensitive to drought, while the parental genotypes – the American variety Coker 254 and the Bulgarian line L 0543, as well as the two newly created Bulgarian hybrids H 27 and H 135 were relatively resistant to drought. These data can serve as a basis for selection and development of new genotypes with increased resistance to drought.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Revision of the Species Bauhinia bulgarica Kitan. fil. (Fabaceae) Known from the Bulgarian Upper Miocene-Lower Pliocene 2022-10-29T13:34:32+03:00 Vladimir Bozukov <p class="p1">A revision of the species <em>Bauhinia</em> <em>bulgarica</em>, which was found in the fossil macroflora of Garmen (SW Bulgaria), is presented. The fossil material originates from sediments dated as Late Miocene-Early Pliocene. The new taxonomic solution is <em>Smilax</em> <em>excelsa</em> L. foss. It is accepted on the basis of the close morphological structure of the fossil leaf imprint and the leaf forms of the recent <em>Smilax</em> <em>excelsa</em> L. (Smilacaceae), which is widespread in the SE Balkan Peninsula and SW Asia.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences In vitro Micropropagation of Helichrysum arenarium (Asteraceae) as a Tool for Introducing the Species in Agriculture 2022-10-29T12:46:08+03:00 Marina Stanilova Boryanka Traykova Vladimir Vladimirov Maria Petrova Ivanka Semerdjieva Elina Yankova-Tsvetkova <p class="p1"><em>Helichrysum</em> <em>arenarium</em>, known as sandy everlasting, is a perennial plant species, used in traditional medicine. In Bulgaria, it is protected by the Biodiversity Act and under a special regime of use based on the Medicinal Plants Act. Seeds from five Bulgarian populations were in vitro germinated and seedlings were sub-cultured on five media supplemented with different plant growth regulators (PGRs) and control MS medium free of PGR. The type of cytokinin turned out to be of crucial importance, as the presence of kinetin stimulated formation of rhizomes and direct organogenesis, BAP caused callogenesis, indirect organogenesis and hyperhydricity, and Meta-topolin – necrosis. Best results were obtained on medium with reduced macrosalt and sucrose concentrations as rhizomes gave rise to numerous well-developed and spontaneously rooted plantlets, up to 55 originating from a single seed. Plants were potted in soil mixture, adapted to phytotron conditions, and transferred to the greenhouse for acclimation, then planted on the ex situ collection. All plants flowered during the first summer outdoor. Nuclear DNA amount was measured by flow cytometry to check possible abnormalities of the in vitro multiplied plants. The estimated DNA amount varied in the range 1C = 0<em>.</em>85–0.89 pg. No deviations in the ploidy level were detected. No difference between the studied populations was found. In vitro micropropagation was shown to be an appropriate method for rapid plant multiplication of <em>H.</em> <em>arenarium</em> thus offering the opportunity for its introduction into agriculture.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences The Effect of HMGB1 Protein and Its Truncated Form on the Expression of RAGE Variants in Breast Cancer Cells 2022-10-29T13:21:27+03:00 Jordana Todorova Maria Petrova Evdokia Pasheva Iva Ugrinova <p class="p1">HMGB1 protein is a DNA binding nuclear protein. Its properties to bind different non-B DNA conformations and also to bend linear DNA implicate the protein in many essential cellular processes as DNA replication, repair, transcription, remodelling, etc. HMGB1 plays important role outside the cell as it is passively released from necrotic cells and actively from apoptotic ones and binds its specific receptor for advanced glycation end products RAGE. HMGB1/RAGE interactin is implicated in various diseases including cancer. Different soluble RAGE forms were reported whose functional role is to serve as a decoy for the ligands and in this way to block the signalling pathway. How the ligands regulate the production of RAGE variants is a subject of great scientific interest. We studied the effect of HMGB1 and its truncated form lacking the C- terminus on the expression of full-length (flRAGE) and soluble RAGE (sRAGE) in breast cancer cell lines: MCF7 represents a hormone dependent cancer with better prognosis and MDA-MB-231 – hormone independent with substantial invasive capacity. HMGB1 stimulates the total RAGE expression in both breast cancer cells but in MCF7 the ratio changes and is in favour of the membrane fraction. The absence of the C-tail of HMGB1 provokes comparable changes in RAGE production in MCF7 cells as the whole HMGB1 molecule. In MDA-MB- 231cell line the total amount of RAGE was slightly affected but it is entirely represented by the membrane form and the soluble one is in negligible amounts.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Ultrastructural Studies on Lamb Liver with Experimental Bunostomosis 2022-10-29T15:50:04+03:00 Yotko Kamenov Kostadin Kanchev Yana Mizinska-Boevska <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>Ultrastructural studies were carried out on liver obtained after the appear- ance of clinical signs of bunostomosis from a group of experimentally infested lambs.</p> <p>In the hepatocytes of the liver severe changes affecting the endoplasmic reticulum, especially the rough one, and the nucleic chromatin were determined.</p> <p>The formation of lipid drops into the injured hepatocytes followed the way of a fat degeneration rather than of a lipid infiltration. Both the liver&nbsp;parenchyma and mesenchyma compounds were affected.</p> <p>This is an evidence of a direct toxic pathogenic action of the etiology agent. These data add to the knowledge of the bunostomosis pathogenesis more information about the leading role of the toxic factor.</p> </div> </div> </div> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Association between the Expression of KISS1, KISS1R and MMP-9 in Invasive Breast Carcinomas 2022-10-29T18:09:09+03:00 Despina Pupaki Svitlana Bachurska Dimitar Parvanov Dessislava Ankova Pavel Rashev <p class="p1"><span class="Apple-converted-space">&nbsp;</span>Metastases are the leading cause of fatal outcome in patients with breast cancer, therefore different proteins related to metastasis are widely studied for the potential to control the spread of cancer cells. It has been shown in various types of cancers that the anti-metastatic role of the KISS1/KISS1R system has been performed by suppressing metalloproteinase 9 (MMP-9) expression, but there is evidence that the relationship between KISS1/KISS1R signalling and MMP-9 in breast cancer seems to be different. The aim of the current study was to assess the association between protein expression of KISS1, KISS1R and MMP-9 using software-based measurement of staining intensity and the possible link to tumour size, grade and receptor status in invasive breast carcinomas. Standard histopathological parameters were determined by an experienced pathologist and immunohistochemical staining for KISS1, KISS1R and MMP-9 was performed on tissue samples from 54 patients. Evaluation of staining intensity was performed using ImageJ software on RGB images by two operators. Results showed significant strong positive correlation between KISS1, KISS1R and MMP-9 and strong expression of studied proteins in tumour associated stromal cells. No association was found between the expression of the studied proteins and size, receptor status or grade. Higher expression of KISS1R, however, was observed in HER2-negative compared to HER2-positive carcinomas, which might indicate an alternative pathway for stimulating pro- proliferation of tumour cells when HER2 expression is low.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Hormonal Status and Bone Health in Bulgarian Adolescents with Secondary Amenorrhoea 2022-10-29T18:50:54+03:00 Diana Hristova Milko Sirakov <p class="p1">A prospective study was conducted including 67 girls with secondary amenorrhoea (excluding cases with PCOS, medical disorders and steroid therapy) and 38 healthy controls. The following indicators were compared between the two groups: serum levels of LH, FSH, estradiol, Ca, P and vitamin D, z- scores for bone mineral density, osteocalcin and <span class="s1">β</span>-CrossLaps, and prevalence of vitamin D deficiency. The group with secondary amenorrhoea was additionally subdivided according to the main cause – alimentary deficiency, excessive physical exercise and stress-induced. LH, FSH and estradiol levels were compared between the three subgroups.</p> <p class="p1">Ca, P and vitamin D levels in the studied and the control groups were not significantly different. The following indicators were significantly lower in the studied group compared to the control one: prolactin (291.74 mIU/ml and 336.24 mIU/ml), estradiol (322.43 pmol/ml and 475.45 pmol/ml) and LH (3.79 IU/L and 4.99 IU/L) levels, LH/FSH ratio (0.55 and 0.96) and z-score (<em>−</em>0<em>.</em>48 and 0.47). FSH was significantly higher in the studied group (6.90 IU/L) compared to the control one (5.44 IU/L). The serum levels of LH and estradiol were significantly lower in the subgroup with secondary stress-induced amenorrhoea (1.73 IU/L and 220.60 pmol/ml) compared to the subgroups with amenorrhoea due to alimentary deficiency (4.68 IU/L and 394.68 pmol/ml) or extreme physical exercise (3.74 IU/L and 323.91 pmol/ml).</p> <p class="p1">In girls with secondary amenorrhea, the levels of osteocalcin were significantly lower compared to the ones in the control group (26.41 and 30.99 ng/ml) while <span class="s1">β</span>-CrossLaps levels were similar (0.34 and 0.98 ng/mL). High prevalence of vitamin D deficiency was observed in both the patients with secondary amenorrhoea (71.6%) and the control group (65.8%).</p> <p class="p1">Significant changes in hormone levels and bone health were observed in Bulgarian adolescent girls with secondary amenorrhoea as well as high prevalence of vitamin D deficiency in both the studied and the control groups. Early diagnosis and timely interventions are needed to improve bone health in adolescents with secondary amenorrhoea.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences The Effect of Bioactive Compounds of Prunus spinosa Leaves and Flowers Mixture on the Antioxidant Capacity in Streptozotocin-induced Diabetic Rats 2022-10-29T19:02:35+03:00 Mehmet Temiz Emine Okumus <p class="p1">Diabetes is a serious and chronic public health problem worldwide. Hyperglycemia leads to the production of free radicals thus impairing oxidant/antioxidant balance and causing various complications in diabetes. Herbs can pro- vide natural remedies against various diseases in traditional medicine. Phyto- chemicals especially phenolic compounds have some biological properties such as antioxidant and antidiabetic effects. Plant parts of <em>Prunus</em> <em>spinosa</em> are used in traditional medicine against various disorders. This study evaluated the mixture of <em>Prunus</em> <em>spinosa</em> leaves and flowers extract (PSE) on the antioxidant capacity in diabetes. The phenolic profile of PSE was determined by HPLC method. Antioxidant capacity was evaluated with radical scavenging activities as well as total phenolic and flavonoid content. Seven random groups (<em>n</em> = 8) of rats were constituted to evaluate the antioxidant capacity – control, diabetic, PSE25, PSE50, insulin, metformin, and acarbose. Total oxidant status (TOS) and total antioxidant status (TAS) were analyzed in the liver tissues. Chlorogenic acid and ellagic acid were found to be the main compound in the mixture of <em>P.</em> <em>spinosa</em> leaves and flowers extract. Antioxidant capacity of PSE exhibited effective radical scavenging activity. Although oxidative stress seriously increased in diabetes, PSE25 and PSE50 supplementation significantly <span class="s1">recuperated liver antioxidant status. In conclusion, PSE markedly has antioxidant capacity through its high phenolic compounds, thus PSE treatment may have potential antioxidant effects for health benefits in diabetes.</span></p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Magnetic Porous Silica-lipid Bilayer Hybrid Carriers for Target Delivery of Curcumin 2022-10-29T12:12:11+03:00 Ivalina Trendafilova Denitsa Momekova Neli Koseva Margarita Popova <p class="p1">Mesoporous silica nanoparticles with embedded magnetic particles and sizes around 80 nm were prepared. Curcumin loading in mesoporous silica was realized by a post-synthesis impregnation procedure. The loaded particles were additionally modified by surface coating with a phospholipid bilayer of a thickness of around 5 nm changing the surface charge of the carrier from negative to positive, which enables the efficient attachment to cells, increasing the probability of cellular uptake. The non-loaded, curcumin loaded and their surface-coated counterparts were characterized by XRD, N<sub><span class="s1">2 </span></sub>physisorption, thermal analysis, TEM, and ATR-FTIR spectroscopy. Release experiments were performed and demonstrated that the phospholipid coating contributed greatly a sustained drug release to be achieved. A comparative study on the antiproliferative effect of curcumin loaded into the mesoporous carrier and lipid-coated vs. free drug was performed on a panel of three human cell lines. On the basis of the obtained results, it can be concluded that obtained hybrid magnetic silica-lipid particles are promising carriers of curcumin.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Detection of Volatile Compounds of (Hyacinth Flowers Hyacinthus orientalis L.) from Turkey 2022-10-29T12:28:19+03:00 Mozhgan Zarifikhosroshahi Zeynep Ergun Sevket Alp Gulsah Ozturk <p class="p1">Hyacinth (<em>Hyacinthus</em> <em>orientalis</em> L.) is one of the most beloved ornamental plants with fragrant flowers. As one of the important bulbous plants, hyacinth is used as a cut flower, potted flower, and garden flower. Due to their unique aroma, hyacinth flowers are used in perfumery especially in France whose perfume industry is well-known in the world. In this study, Headspace Solid Phase Micro Extraction (HS-SPME) GC/MS (Gas Chromatography/Mass Spectrometry) technique was used for the analysis of volatile compounds of flower samples. A total of 28 volatile compounds were identified in the fresh flowers of hyacinths. Phenylethyl alcohol, benzyl acetate, a-pinene, and furfural were the major aromas accounting for hyacinth fragrance.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Compact Low-dropout Linear Regulator Design in 0.13 µm CMOS Technology for IoT Based Remote Infectious Disease Monitoring System 2022-10-29T14:03:36+03:00 Khairun Minhad Mohammad Bhuiyan Tan Ding Mohammad Hemel Omar Dawi Mamun Reaz Mahdi Miraz <p class="p1"><span class="Apple-converted-space">&nbsp;</span>With the widespread adoption of the internet of things (IoT), power management of the different electronic (i.e. IoT) devices has become a major challenge. The low-dropout linear regulator (LDO) circuit is widely used for power management applications of electronic devices. This article reports the design and simulation of a low-dropout linear regulator (LDO) circuit, powered by a 1.2 V DC power supply voltage. In order to optimise the power dissipation, low layout silicon area and lower dropout voltage, a current mirror based transistor optimised LDO circuit has been implemented. The simulation results show that the proposed LDO regulator circuit exhibits a 582 mV low-dropout voltage, 1.568 mW power dissipation, and a very compact layout silicon area of 163.84 µm <sup><span class="s1">2</span></sup>(12<em>.</em>795 <em>×</em> 12<em>.</em>805 µm). The proposed LDO linear regulator archi- tecture is designed and validated in 0.13 µm TSMC CMOS process technology using Mentor Graphic EDA tools.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Analysis of Cell Proliferation and Apoptosis in Virtual Model 2022-10-29T14:29:48+03:00 Suji Jalajakumari Swathi Devaraj Thangatamilan Manivel Sureshkumar Ramasamy <p class="p1"><span class="Apple-converted-space">&nbsp;</span>Breast cancer is the second leading cause of cancer among women globally. Several treatments are involved in breast cancer like surgery, chemotherapy, radiotherapy, and hormone therapy; chemotherapy being used most often. Multicellular systems complications can be deeply understood by analyzing and studying how cells grow, move, divide, die and interact. To examine these factors, we use PhysiCell as our modelling platform. Virtual cell growth analysis is essential to view the cancer cell growth daily. PhysiCell physics-based multicellular simulator is an open-source agent-based simulator used to design a virtual model to analyze the changing cell cycle progression, volume, death, motility, mechanics and processes. Analysis was made on the cancer cell death rate, cell damage rate, and cell repair rate. Data were taken for every 6 hours of simulation and the result confirms that the chemotherapeutic agent kills 45% of cancer cells.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Modelling of Different On-chip Inductors for Radio Frequency Integrated Circuits 2022-10-29T14:51:44+03:00 Dhamodaran Muneeswaran Jegadeesan Subramani Thanapal Pandi Navaneethan Chenniappan Meenatchi Shanmugam <p class="p1"><span class="Apple-converted-space">&nbsp;</span>This paper presents a typical frequency-dependent modelling of different on-chip inductors for RFICs design problems. Modern RF circuits often feature on-chip inductors required by modern circuit design. A comparison of different inductor geometrics includes a planar spiral inductor and novel multilayer inductors are analyzed. An electromagnetic model with fewer assumptions than empirical equations and higher efficiency than full-field solvers would be welcome. So would facile comparisons of different inductor structures. This paper describes recent work on the electromagnetic modelling of on-chip inductor structures, applied to the comparison of inductor geometries, including the traditional spiral inductor and a novel multilayer inductor. The electromagnetic modelling of the investigative model is also presented.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences Static-dynamic Tests of Bearing Capacity of Wind Turbine Piles 2022-10-29T15:33:50+03:00 Mladen Cosic Nenad Susic Ksenija Djokovic <p class="p1"><span class="Apple-converted-space">&nbsp;</span>The paper presents the static load tests (SLT) and dynamic load tests (DLT) of the piles and numerical analyses of piles in interaction with the soil of wind turbines. Pile tests were conducted using the equipment with counter-weights for SLT and an autonomous system for the control of DLT of the piles. Numerical DLT analyses were performed by the signal matching method. Tests proved that the design resistance of piles of SLT and mobilized static resistance of DLT are higher than the design forces obtained from the design of the wind turbine foundations. Also, the need to develop a plan for testing the bearing capacity of piles, concerning large and significant buildings was emphasized.</p> 2022-10-30T00:00:00+03:00 Copyright (c) 2022 Proceedings of the Bulgarian Academy of Sciences