|B. V. Toshev|
2019: Two Important Events
Full text: PDF (330 K)
|Education: Theory & Practice:|
|E. Karashtranova, N. Karashtranov, V. Vladimirov|
A Content Analysis of the Results from the State Matriculation Examination in Mathematics
Full text: PDF (854 K)
Variants in Learning Based on Constructivism [In Bulgarian]
Full text: PDF (382 K)
|E. Karashtranova, N. Karashtranov, N. Borisova, D. Kostadinova|
Some Concepts from Probability and Statistics and Opportunities to Integrate Them in Teaching Natural Sciences
Full text: PDF (1145 K)
|Patiha, M. Firdaus|
Review and Improved Technique of the Initial Rate Method
Full text: PDF (817 K)
|D. Tasheva, P. Vassileva|
45-th International Chemistry Olympiad [In Bulgaria]
Full text: PDF (1397 K)
|From the Research Laboratories:|
|S. N. Chaulia|
Semi-Empirical Computational Study of the Ligand Metal Complexes Derived from 4-Aminoanthipyrine and 2-4-Dihidroxy Benzoic Acid
Full text: PDF (862 K)
|V. Pencheva, S. Penchev, L. Ivanov|
Advances of Photothermal Microscopy of Composite Magnetoelectric Nanolayers Using Laser Heterodyne Probe
Full text: PDF (1545 K)
Considerations on DADNE Isomers - A DFT Treatment
Full text: PDF (1461 K)
|M. Kumar, A. Rani, R. Khare, H.S. Tuli, S. Arora, R. Kumar|
6,6',8.8'- Tetramethyl - 4,4',7,7'- Tetrahydros-7,7'- Bi-1,2,4,5- Tetrazocine- 3,3'(2H,2'H)- Dithion, A Novel Hydrazone Schiff Base with Promising Pharmacological Effects
Full text: PDF (931 K)
Khimiya, Volume 28, Issue 1(2019)
Khimiya. 28, 9-15 (2019) Author(s): E. Karashtranova, N. Karashtranov, V. Vladimirov:
Abstract.This paper presents an analysis of the results from the State Matriculation Examination in Mathematics achieved by the students from the Science and Mathematics High School “Acad. S. Korolyov” within the period of 2012-2014.
Keywords: mathematics education
Khimiya. 28, 16-26 (2019) Author(s): Y. Klissarov:
Abstract.Constructivism is the methodological basis of active learning and its variants: learning by experience, learning by doing, autonomous learning, contextual learning, problem solving and problem-based learning, project-oriented learning, collaborative learning and learning through interaction. Common characteristics is solving real-life problems taking into account individual differences of learners - learning styles, learning abilities, motivation. The developed interactive learning environment is considered to be the media for social interaction and cooperation, providing a lot of opportunities for each student to choose and contribute. Thus new knowledge integrates into existing structures, experience is gained to be tested in various situations. Student achievement and development of their independent cognitive activity, however, are dependent on teacher’s competences.
Keywords: constructivism; problem-solving; action-oriented approach; ask-based activities
Khimiya. 28, 27-33 (2019) Author(s): E. Karashtranova, N. Karashtranov, N. Borisova, D. Kostadinova:
Abstract.The aim of the suggested approach is to focus on acquisition of elements of Probability and Statistics that are included in the curricula of Mathematics, Informatics and Information Technologies in Bulgaria. The educational tools offered show the opportunities for co-related education in Informatics and Statistics. The approach used for the development of educational materials allows a quick and flexible reaction to the changes in education.
Keywords: teaching Probability and Statistics in Bulgaria; simulation modules; educational tools
Khimiya. 28, 34-47 (2019) Author(s): Patiha, M. Firdaus:
Abstract.It is claimed that, in certain circumstances, initial-rate method (IRM) has advantages over the integral method (IM). But, the IRM will only be effective if the concentration change is less than 5 % and the rate constant (k) obtained should be checked with IM. There are two main purposes of this research. First, to prove that the claim is invalid and the IRM can be used on broader concentration changes. In addition, the rate law model used in the claimed is invalid for reaction that takes place in two mechanisms. Second, to find a new form of IRM equation, which does not require IM checks. This study used the oxidation of formic acid with bromine as a reaction model. The values of n and k of this reaction at two mechanisms were determined by the IM, and then by the conventional IRM, the method used in the claim, and by the new IRM generated by this study. All of k values are compared by using IM as the standard. The proposed method is claimed valid if the error percentage of k is less than 5 %. Despite the shortcomings, the results show that the new IRM is valid and more reliable.
Keywords: initial rate method; integral method; rate constant; reaction order
Khimiya. 28, 48-93 (2019) Author(s): D. Tasheva, P. Vassileva:
Abstract.The paper represents problems (theoretical and practical) of the 45th International Chemistry Olympiad and the solutions of theoretical problems. Comments of Bulgarian team presentation are given.
Keywords: International Chemistry Olympiad (IChO); practical exam; theoretical problems and solutions
Khimiya. 28, 94-108 (2019) Author(s): S. N. Chaulia:
Abstract.Theoretical molecular structures of the ligand and its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been studied using the semi-empirical quantum chemical methods. The experimental IR, electronic and NMR data of the investigated compounds are compared with the computational data. The ESP map and the natural atomic charge of the ligand was calculated to ascertain the reactive sites of the ligand. The experimental data agree well with the computational data.
Keywords: MEP, natural atomic charge, correlation coefficient, AM1, PM3
Khimiya. 28, 109-118 (2019) Author(s): V. Pencheva, S. Penchev, L. Ivanov:
Abstract.A theoretical solution advances the potential for photothermal microscopy of nanostructured composite magnetoelectrics and high- temperature superconductors. Photothermal displacement (PTD) is a sensitive effect employed as a fingerprint of the physical and structural properties of a variety of prospective materials. Thermal- diffusion model is developed for the general case including opaque and also transparent probes. Laser double- heterodyne technique is employed to improve the resolution of PTD measurement. The excessive noise is eliminated to the level viable to detect structural inhomogeneities and thickness of nanolayers up to 0.1nm. The method is applicable to nanolayers deposited on opaque substrates, as well, transparent substrates with large gradient of refractive index of the interface. Very good agreement between experimental results and theoretical prediction is achieved. The developed laser scheme is particularly feasible for non- destructive measurements of samples at operational conditions and restricted access.
Keywords: photothermal; laser; heterodyne; magnetoelectric; nanolayer
Khimiya. 28, 119-140 (2019) Author(s): L. Turker:
Abstract.Isomers of diaminodinitroethylene (DADNE) are subjected to quantum chemical treatment within the realm of density functional theory at the level of B3LYP/6-311++G(d,p). Mono anions and cations of them are also considered (UB3LYP/6-311++G(d,p)). The possibility of cis-trans isomerization is analyzed. Some quantum chemical properties, IR and UV-VIS spectra, some ballistic properties etc. are mentioned.
Keywords: DADNE; FOX-7; DADE; explosives; DFT calculations; isomers; ions
Khimiya. 28, 141-154 (2019) Author(s): M. Kumar, A. Rani, R. Khare, H.S. Tuli, S. Arora, R. Kumar:
Abstract.Novel hydrazone Schiff base viz. 6,6',8,8'-tetramethyl-4,4',7,7'-tetrahydro-7,7'-bi-1,2,4,5-tetrazocine-3,3'(2H,2'H)-dithionehas been synthesized from3,4-diacetylhexane-2,5-dione and thiocarbohydrazideandcharacterized. The bicyclichydrazone Schiff basehas been found active against bacteria[S.aureus and K.pneumoniaae] and fungi [A.niger and Trichophytonrubrum]. DNA photo-cleavage and antiangiogenic behavior of synthesized hydrazone Schiff base has been studied. Furthermore,the synthesizedhydrazone Schiff basesignificantly inhibited cell proliferation with IC50 value 62.5μg/ml. The flow-cytometry analysis of hydrazone Schiff base treated human breast cancer cells showed that apoptosis rate increased with increase in dose. In conclusion present study proposes the development of novel therapeutic strategy for MCF-7 cancer cell treatment.
Keywords:3,4-diacetylhexane-2,5-dione;thiocarbohydrazide; antimicrobial activities; anti-angiogenesis; DNA-cleavage and anti-proliferation