Letters to the Editor
On the Placement of Hydrogen and Helium in the Periodic Sistem: A Comment
J. Cvetkovic, V. M. PetrusevskiВлезте в системата, за да прочетете пълната статия
Education: Theory & Practice
Students’Scientific Literacy at the Beginning of 21st Century: In Search of Conceptual Unity [In Bulgarian]
Резюме. The aim of this study is to analyze the most frequently used definitions of the term „scientific literacy“ in the specialised literature and be integrated into a holistic construction essential features which are commonly identified. The methodological basis of the study are the ideas of epistemological constructivism. The theoretical analysis is focused on the definitions of the concept „scientific literacy â€œ in primary literature sources â€“ articles and documents of international organizations as related to school science education. It has a focus on definitions of the early 90s of the 20th century and especially those after the beginning of the 21st century â€“ the time of intensive educational reforms globally whose general trend is to develop scientific literacy for all students. We have found common aspects between the different definitions by comparing of preliminary extracted components which function as criteria and indicators in the analysis undertaken: (1) Knowledge â€“ factual and conceptual knowledge of the natural world; understanding of the nature of science. (2) Skills and abilities â€“ scientific inquiry of nature phenomena in school setting; solving and decision-making on socio-scientific issues in learning context; communication and collaboration with others. (3) Attitude and behavior â€“ awareness and evaluation of the interactions between science, technology and society; value attitudes and responsible behavior towards the environment. (4) Metacognition â€“ metacognitive knowledge and metacognitive skills. The results of the analysis are the basis for designing a general model which presents our views of scientific literacy in the early 21st century as a holistic construct. It brings together four interrelated dimensions â€“ cognitive-epistemic, functional, social and metacognitive. These dimensions operate simultaneously in certain context (personal, social and/or global) with leading and integrating role of metacognition.
Keywords: scientific and science literacy, science and technology, school science education
T. Kolarova, I. Hadjiali, M. Dokova, V. AleksandrovВлезте в системата, за да прочетете пълната статия
Education: Theory & Practice
Use of Competence Ontological Model for Matching of Qualifications
Резюме. The ontological representation of competence knowledge about various specialties (from national qualifications frameworks) for their efficient matching and retrieval for the purpose of the European and National Qualifications Frameworks transparency is represented. The structure of atomic competencies is formalized by ontology that can be automatically built by semantically marked Web resources from the Semantic Media Wiki environment. Computer ontologies and methods of their use to ensure the transparency of the European and National Qualification Frameworks are suggested.
Keywords: ontology, competence, qualification, Semantic Web, Wiki.
J. Rogushina, S. PryimaВлезте в системата, за да прочетете пълната статия
Computer Simulations: Application for Graduates’Adaptation at Oil and Gas Refineries
Резюме. The present paper is devoted to analysis of computer simulators efficiency in terms of graduatesâ€™ adaptation at oil and gas refineries. The experience of such modeling system implementation shows that through the use of a computer simulator based on interactive simulation system we can reach high levels of enterprise employees professionalism in a short time. This, in turn, reduces the risk of abnormal and emergency situations and can finally reduce the cost of production. It will also be possible to increase the fault tolerance of the equipment by reducing the influence of the human factor and clarify regulatory requirements for the installation, including the start, emergency stop, and regular and emergency situations.
Keywords: chemical technology, computer simulators, refineries
T. O. Dolganova, I. M. Dolganov, K. A. VasyuchkaВлезте в системата, за да прочетете пълната статия
Boson/Fermion Janus Particles
Резюме. Thermodynamically, bosons and fermions differ by their statistics only. A general entropy functional is proposed by superposition of entropic terms, typical for different quantum gases. The statistical properties of the corresponding Janus particles are derived by variation of the weight of the boson/fermion fraction. It is shown that di-bosons and anti-fermions separate in gas and liquid phases, while three-phase equilibrium appears for poly-boson/fermion Janus particles.
Keywords: entropy, bosons, fermions, Janus particles
R. TsekovВлезте в системата, за да прочетете пълната статия
Activation Energy [In Bulgarian]
Резюме. A number of inaccuracies and errors on such an important concept of chemistry, as the activation energy of chemical reactions, have found a place in textbooks and academic documents. This article provides the necessary clarifications for adequate consideration of the concept of energy of activation; with using this method a close understanding of this basic concept in Chemistry would be expected.
Keywords: activation energy, chemical kinetics, influence of temperature, catalysis
B. V. ToshevВлезте в системата, за да прочетете пълната статия
Synthesis, Characterization and Biological Activities of Pyrazolyl Copper(II) Nitrate Complexes
Резюме. Three pyrazolyl copper(II) complexes vz. diaqua-bis(3-ferrocenyl-1H-pyrazole)-dinitrato-copper(II) (C1), diaqua-(3-ferrocenylpyrazolyl-1-methylene pyridine)-dinitrato-copper(II) (C2) and diaqua-bis(3-phenyl-1H-pyrazole)-dinitrato-copper(II) nitrito (C3) have been synthesized and characterized by IR spectroscopy, UV-vis, thermogravimetric analysis, melting point determination and magnetic measurements. The complexes were obtained in low to high yields and the combination of various techniques suggests that these complexes show an octahedral geometry with coordination via two nitrogen atoms from the pyrazolyl ligand, two oxygen atoms from water molecules and two oxygen atoms from the nitrate group. All complexes are thermally stable in the temperature range of 80-100oC. The antimicrobial activities were screened using a range of gram negative and gram positive bacteria and fungi. It was observed that all the complexes have anti-microbial activities against studied microbes.
Keywords: pyrazole, copper, nitrate, anti-microbial activities
A. Munyaneza, G. Kumar, I. C. MorobeВлезте в системата, за да прочетете пълната статия
Synthesis of New [(3-Nitro-2-Oxo-2H-Chromen-4-Ylamino)-Phenyl]-Phenyl-Triazolidin-4-Ones and Their Antibacterial Activity
Резюме. A series of reactions that result in the synthesis of novel thiazolidynones based on 4-chloro-3-nitrobenzopyran-2-one is presented in this study. During the condensation reaction of 4-chloro-3-nitrobenzopyran-2-one 2 and benzene-1,4-diamine, 4-(4-Amino-phenylamino)-3-nitro-chromen-2-one 3 is synthesized in high yield. By catalytic condensation of product 3 and benzaldehyde, salicylaldehyde and 3-nitrobenzaldehyde, novel derivatives of 4-[4-(Benzylidene-amino)-phenylamino]-3-nitrobenzopyran-2-one, 4(a-c), as condensation products are synthesized. In the following series of reactions, by cyclization of the products 4(a-c) and 2-mercaptopropionic acid, corresponding substituted thiazolidinones 5(a-c) are synthesized. Determination of structure of the synthesized products is done on the basis of spectrometric data. Compounds 4(a-c) and 5(a-c) are examined for their antibacterial activity against S. aureus, E. coli and Klebsiella by measuring the zones of inhibition around the disks impregnated with the corresponding solutions of compounds in N,N-DMF concentration 2 mg/mL, 4 mg/mL and 6 mg/mL. Compounds of series 4 have shown moderate antibacterial activity against these microorganisms, whereas compounds of series 5 have shown significant activity. The impact of substitutions in antmicrobial activity is also explored.
Keywords: thiazolidin-4-one, benzopyran-2-one, cyclization, inhibition zones
R. Hoti, H. Ismaili, I. Vehapi, N. Troni, G. Mullqi-Osmani, V. ThaciВлезте в системата, за да прочетете пълната статия
From the Research Laboratories
Stability of RJ-5 Fuel
Резюме. In this work, the stability of a bicyclic high-energy-density fuel, RJ-5 (C14H18), has been inspected. The tendency of RJ-5 jet fuel to form hydroperoxide structure under storage conditions has been examined. The negative âˆ†Gorxn values showed that oxidation of fuel through hydroperoxidation is a spontaneous process. It was shown that the bridgehead carbon atoms and the carbon atoms that link the norbornane structure with the other ring system are the vulnerable centers to hydroperoxidation because the corresponding hydroperoxides are quite low in total electronic energies. The thermodynamic calculations showed that these hydroperoxide structures may rearrange themselves to minimize their energy forming different molecules. These rearranged molecules have been identified using rearrangement mechanism in the literature. The probable rearrangement products were determined and confirmed by thermodynamic calculations. The heat of combustion values of RJ-5, hydroperoxides and rearrangement products of hydroperoxides have been calculated using T1 heat of formation data. The results showed that the formation of hydroperoxide molecules under storage conditions worsens the performance of RJ-5 jet fuel.
Keywords: jet fuel, RJ-5, oxidation, hydroperoxidation, rearrangement
L. Turker, S. VarisВлезте в системата, за да прочетете пълната статия
Science and Society
A Study of Begliktash Megalithic Complex
Резюме. The article presents the results of interdisciplinary study of megalithic complex Begliktash conducted by a group of researchers from the University of Shumen. The main conclusion is that Begliktash is a natural phenomenon with interesting stone complex morphology that may have been artificially consolidated and used both to perform rituals and for calendar purposes.
Keywords: Begliktash, megalithic complex, community
D. Kyurkchieva, E. Stoykov, S. Ivanov, B. Borisov, H. Hristov, P. Kyurkchiev, D. Vladev, I. IvanovaВлезте в системата, за да прочетете пълната статия