Letters to the Editor
48th National Conference of Chemistry Teachers [In Bulgarian]
E. Boiadjieva
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Digitalization of Education: Necessity and Problems [In Bulgarian]
Z. Kostova
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Laser Micro-Perforation and Fields of Application
Absract. Replacing of conventional technology for producing microfilters with a laser technology is presented in the paper. Two approaches for laser drilling through melting and sublimation are discussed. The paper describes possibilities of laser technology in obtaining filters and sieves with different diameters of the holes in the microwave range as well as high homogenity of structures. Detailed analysis of photo-etching as an alternative to laser drilling of microfilters with a certain geometry has been carried out. Advantages and disadvantages of the most common technologies are shown, too.
Keywords: laser, microsieves, microfilter, photo etching, laser drilling
H. Deneva, L. Lazov, E. Teirumnieks
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Elaboration of a Lab Ecercise to Analyze the Characteristics of Photovoltaic Panels Through a V-I Electronic Unit
Absract. A lab exercise has been developed to teach students how to monitor and analyze basic characteristics of a photovoltaic (PV) panel. The exercise configuration is based on an electronic unit, previously constructed and reported by the authors. It is applied to measure and record the PV panel voltage at different current loads. Then the Volt-Ampere (V-I) and the output (P-V) characteristics of a PV panel are analyzed. The procedures are done for different light sources and different filters. The analysis and the visualization is executed by a software, developed previously by the authors.
Keywords: lab exercise; photovoltaic panel; current vs. voltage characteristic; power output vs. voltage characteristic
D. K. Gospodinov, D. A. Zlatanski, S. I. Sotirov
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Chitosan / Alginate Complexes Prepared by Jet Mixing [In Bulgarian]
Absract. The influence of mixing procedure on the size of polyelectrolyte complexes (PECs) was investigated using modified jet mixing complexation technique. Two natural weak polyelectrolytes – chitosan and alginate were used for PECs formation. All the experiments were done with 0.1% solution of the polyelectrolytes in acetate buffer with pH 5 and ionic strengths 0.1 M. The average particle diameter was determined by the method of dynamic light scattering using the Microtrac Nanotrac Wave Particle Size, Zeta Potential and Molecular Weight Analyzer. It has been found that decreasing the diameter of the outlet tube, which brings PEC out from the mixing chamber, and increasing its length, reduces the average diameter of the complex that is in the nano-size range. Mixing at a higher pressure in the chamber, which depends on the open state of the jets at the same tube geometry, also results in the formation of smaller PECs. Possible explanation for the observed phenomenon could be the tendency of PEC to aggregate at lower velocities and longer mixing times.
Keywords: jet mixing; nanoparticles; polyelectrolyte complexes
M. Marudova, S. Sotirov, B. Pilicheva
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Applied Photonics and Antioxidant Properties of High Oleic Sunflower Oil with Herbs [In Bulgarian]
Absract. Physico-chemical and optical properties of sunflower oil with basilicum (Ocimum basilicum), rosemary (Rosmarinus officinalis) and walnut oil have been investigated. Adding herbs to the sunflower oil increases the content of polyunsaturated fatty acids β-carotene and chlorophyll. The sunflower oil with basilicum (Ocimum basilicum) shows a fluorescence peak at about 555 nm, which is due to the high β-carotene content. All samples show a peak between 741 nm and 746 nm range, which is due to pigments different from chlorophyll, and those containing herbs and a chlorophyll peak at about 683 nm.
Keywords: fluorescence, sunflower oil, oxidant stability, fatty acid composition
K. Nikolova, S. Minkova, P. Radusheva, G. Boshev, E. Faridin, N. Dzhambazov, M. Perifanova-Nemska
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The Diffusion as a Base of Dialysis [In Bulgarian]
Absract. The aim of this paper is to present the nature of the processes osmosis and diffusion, their crucial part in the excretory system of the living organism as well as the physical principles behind dialysis. There are two methods of dialysis – hemodialysis and peritoneal dialysis.
Keywords: diffusion; osmosis; dialysis; medical applications
B. Sabit, D. Dervish, M. Nikova, Y. Eneva
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In Vitro Evaluation of the Antioxidant Properties of Olive Leaf Extracts – Capsules versus Powder
Absract. The olive leaf extract has been known for its healing abilities since ancient times, when it was used to brew tea and to treat multiple conditions. In modern times it is advertised as a natural source of antioxidants which have a positive effect on human health. The extract is offered on the market as a food supplement by many different manufacturers and can be found in either capsulated or bulk form. The purpose of this experiment is to compare the antioxidant effect of the extract in relation to the form in which it is. The effect was tested in two separate systems for evaluation of total antioxidant activity – ABTS and DPPH. It was established that the extract marketed in capsulated form has better antioxidant properties than the bulk form. The tests in biologically relevant systems showed that while both forms have strong antioxidant abilities, the capsulated form achieves the same biological effect in smaller doses of the extract. The carried out experiments in all tested systems proved that the antioxidant effect of the capsulated form is stronger than the bulk one. The difference in antioxidant activity is most likely due to the protective properties of the capsule.
Keywords: antioxidant; olive leaves extract; free radicals; chemiluminescence
H. Saint-James, G. Bekova, Z. Guberkova, N. Hristova-Avakumova, L. Atanasova, S. Alexandrov, T. Traykov, V. Hadjimitova
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Model of Contentive and Technological Integration Applied in Environmental Education [In Bulgarian]
Absract. The problem concerning unity of scientific knowledge and hence its transformation into educational knowledge is not new to research. In recent years, the idea of implementing this unity has been present in the normative documentation for the management of pre-school and school education. The question remains how the concept of integration is materialized in the aforementioned documentation, and especially how it is technologically enshrined in the practice of training. The article presents a comprehensive model for integration, which is in the intersection of formal and non-formal education and its professional pedagogical decoding in three interconnected sections – normative, contentive and technological. In these three sections, integral constructs are brought out as a new kind of entity aimed at forming students’ cognitive, affective, reflective and social skills through content-based emphasis in environmental education.
Keywords: integration, standard, skills, environmental education
K. Doychinova, N. Raycheva,
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Remarks on the Normative Provision of the Process of Learning in School [In Bulgarian]
Absract. The present article presents regulatory requirements for school assessment of students regulated by Regulation No. 11 of 01.09.2016. The forms, types, manner and classifications of assessment are discussed in the article. The general provisions, principles and institutes in the process of assessment in the school education system, the action and force of the new Ordinance are considered. A comparative study with the previous Regulation No. 3 of April 15, 2003 is made in order to present the dynamics of change of the educational policy in the assessment system at schools. Some de lege ferenda proposals for legislative changes are made in order to improve the cited legal framework. Due to its ontological nature, the present article does not discuss the problems of the assessment of students with Special Educational Needs (SEN) and students studying arts and sports. In order to avoid unnecessary repetition, it is assumed that all texts that do not cited by law are texts from Regulation No 11 of 01.09.2016.
Keywords: regulation; education policy; assessment; schools
R. Angelov, S. Traykova
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Analysis of the Results of the External Assessment of ‘Gepgraphy and Economy’, 5th Grade – Years 2017 and 2018 [In Bulgarian]
Absract. The article presents and analyzes the achievements of the pupils from the 2017 and 2018 external evaluations of geography and economy in Vth grade. Some tricky educational requirements in the new subject curriculum are highlighted. The expert opinions, expressed during the public discussion of the new curriculum, are compared with the obtained results.
Keywords: geography education; external evaluation; curriculum; educational requirements and achievements
I. Drenovski, I. Ruseva
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Paracelsus in the History of Chemistry, Medicine and Pharmacy [In Bulgarian]
Absract. Philippus Aureolus Teophrastus Bombastus von Hohenheimm, known also as Paracelsus, is one of the most eminent representative of European alchemy. His achievements and fragments of the course of life are both presented in the present article.
Keywords: alchemy, iatrochemistry, history of chemistry, history of medicine, history of pharmacy, Middle ages, Renaissance
N. R. Stepanov
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2019 – The International Year of the Periodic Table of Chemical Elements
Absract. The 150th anniversary of the discovery of Periodic Table of chemical elements by Dmitri Mendeleev in 1869 will be celebrated in 2019 year. The key role of Mendeleev’s work on elements systematization is presented in brief together with the indispensable efforts of many other chemists too. Different types of Periodic tables and the development of ideas concerning the structure of a table or other graphical representations of the existing state-of-art over years are shown in a more historical point of view.
Keywords: 150th anniversary; periodic table; history of discovery; Dmitri Mendeleev
M. Atanassova, R. Angelov, D. Gerginova, A. Zahariev
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Technology (Schattzberg, 2018) [In Bulgarian]
Absract. In modern life, technology is everywhere. But what is it? In this book Erik Schatzberg explains why technology is so difficult to define by examining its three-thousand-year history, one shaped by persistent tensions between scholars and technical practitioners. Since the time of the ancient Greeks, scholars have tended to hold technicians in low esteem, defining technical practices as mere means toward ends defined by others. Technicians, in contrast, have repeatedly pushed back, insisting on the dignity, creativity, and cultural worth of their work. The tension between scholars and technicians continued from Aristotle through Francis Bacon and into the nineteenth century. It was only in the twentieth century that modern meaning of technology arose: technology as the industrial arts, technology as applied science, and technology as technique. The author traces these three meanings to the present day, when talk about technology has become pervasive, but conclusion among the three principle meanings of technology remains common. The author shows that only through a humanistic concept of technology can we understand the complex human choices embedded in our modern world.
Keywords: technology, history of technology, contemporary issues
B. V. Toshev
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