|Letters to the Editor:|
SCIENTIX: Community for Science Education in Europe [In Bulgarian]
Full text: PDF (512 K)
|M. Boycheva, R. Davidova|
How to Develop Pupils' Cognitive Interest on the Basis of the Subject "Man & Nature: Structure and Life Processes of Organisms": In-service Training of Teachers without Biological Education. III [In B
Full text: PDF (367 K)
|N. Dankova, R. Bencheva, I. Kovachev|
Interdisciplinary Lessons: Astronomy with Belles Lettres and Information Technologies [In Bulgarian]
Full text: PDF (324 K)
Diagnostics of the Environmental Culture of Pupils: A Case Study - Teaching of the VI-a Group of the Periodic Table in 8th Grade [In Bulgarian]
Full text: PDF (451 K)
Higher Education Perspectives for an Exciting Educational Experience - Part III: An Indian Context
Full text: PDF (713 K)
|V. Kant, H. Shekhar|
Thermodynamic and Interfacial Studies on Co-crystals of Nicorineamide - Thiourea Drug System
Full text: PDF (626 K)
A Comparative Evaluation of the Methods Used for Redox Equations Balancing: Asvantages and Disadvantages [In Bulgarian]
Full text: PDF (386 K)
|H. Popova, D. Petkova, V. Tonchev|
Generic Instability in the Model of Diffusion-Limited Aggregation (DLA): The Effect of Global Radii of Birth and Killing [In Bulgarian]
Full text: PDF (873 K)
|Personalities in Science:|
|Z. Kostova, M. Topashka-Ancheva|
Botyu Atanassov Botev [In Bulgarian]
Full text: PDF (1040 K)
|History and Philosophy of Science:|
|M. Atanassova, R. Angelov|
Chronology of Chemical Elements Discoveries
Full text: PDF (793 K)
With Rocket Grenade to the Moon in the Year 3000 AC (1929) [In Bulgarian]
Full text: PDF (2087 K)
Khimiya, Volume 23, Issue 2(2014)
Khimiya. 23, 177-185 (2014) Author(s): M. Boycheva, R. Davidova:
Abstract.The aim of this study was to design learning and cognitive tasks which would be used for developing cognitive interests of the students to their primary biological education. The teachers trained are without a special biological education. The school subject is “Man & Nature: Structure and Life Processes of Organisms.” The proposed methodological constructions make no claim to be universal and should be used only as models which are subject to creative improvement or adaptation by the teacher according to the concrete pecu liarities of the teaching process.
Keywords: pupils’ cognitive interest, “Man & Nature”,teachers without biological education
Khimiya. 23, 186-191 (2014) Author(s): N. Dankova, R. Bencheva, I. Kovachev:
Abstract.A good practice in school in combining astronomy with belles lettres and information technologies is shared. It is expected to be a good way to motivate students to learn science.
Keywords: astronomy, literature, information technology, interdisciplinary
Khimiya. 23, 192-207 (2014) Author(s): A. Angelacheva:
Abstract.The educational research is realized on the basis of a criterion test “VI-A Group of the Periodic Table”. The item-analysis is carried out following the methods: (a) expert evaluation of content validity and standard of successfulness of the test; (b) analysis the results of the test trial in a representative sample of pupils in the 8th grade. The empirical data show that the test has good statistical characteristics and can be used for effective diagnostics of the environmental culture of students.
Keywords: ecological culture, didactical tools, chemistry education, environmental education
Khimiya. 23, 208-231 (2014) Author(s): B.H.S. Thimmappa:
Abstract.In a modern industrialized society science education plays an important role in the progress of the country and protection of the environment. The quality of higher education in India needs substantial improvement through vision and proper planning. It is necessary to introduce a series of major educational initiatives that have immense scope for value addition and enhancing learners’ involvement in the educational activities to leave a lasting impression. An attempt has been made to indicate appropriate changes in the higher education system and arouse the interest of the young aspirants in science in their educational journey. The current paper highlights the salient features of science higher education perspectives in an Indian context. The implementation of the modern educational practices will open up a new window to explore science in its true sense and perspective. The innovative educational schemes for development of science higher education and achieving excellence go a long way in making learning an enjoyable, exciting and memorable experience.
Keywords: E-resource, teaching tools, enhanced understanding, active participation, vibrant curriculum, educational significance, contemporary practices
Khimiya. 23, 232-247 (2014) Author(s): V. Kant, H. Shekhar:
Abstract.The present communication aims at investigating the Nicotinamide (NA) – Thiourea (TU) binary system in the solid state emphasizing thermodynamic and interfacial studies. It was found from the solid-liquid phase diagram of the system that an A 1:5 additive co-crystal formed at 161°C and two side by side eutectic solid dispersions E2 (mole fraction 0.407 of TU) and E1 (mole fraction 0.968 of TU) at 142°C and 116°C respectively. The activity coefficient model based on enthalpy of fusion was employed to calculate the excess thermodynamic properties that of gE, hE and sE, which predict the nature of molecular interaction, ordering and stability between the components. The negative value of integral Gibbs free energy of mixing, ΔGM for all the eutectic and non-eutectic solid dispersions favours the spontaneous mixing in all solid dispersions. The driving force of nucleation during solidification (ΔGv) and the critical free energy of nucleation (ΔG*) at different undercoolings have also been highlighted. The value of radius of critical nucleus (r*) of solid dispersions has been found in nm scale which suggests new dimensions of solidification process for nano solid drug dispersions and it would be very surprising for the pharma world. The solid-liquid interface energy (σ), grain boundary energy (σgb) and the Gibbs-Thomson coefficient (τ) of all drug alloys have also been discussed. Interface morphology of the alloys follows the Jackson’s surface roughness (α) theory and predicts the faceted growth (α > 2) proceeds in all the cases.
Keywords: phase diagram, thermodynamic excess and mixing functions, critical radius, interfacial energy, roughness parameter
Khimiya. 23, 248-259 (2014) Author(s): I.L. Dukov:
Abstract.The advantages and disadvantages of the methods for redox equations balancing have been commented and supported by suitable examples. Although the oxidation number method and half reaction method show some limitations, they can be applied for balancing of a large number of redox reactions. The material balance method (algebraic method) is the most universal method. It can be applied for balancing of all type reactions. The modified form of the method permits to reduce considerably the algebraic calculations and is suitable for complex redox reactions balancing.
Keywords: redox reactions, oxidation number method, half reactions method, material balance method
Khimiya. 23, 260-268 (2014) Author(s): H. Popova, D. Petkova, V. Tonchev:
Abstract.We construct a simple model of diffusion-limited growth of two 1D clusters with common birth and killing radii without exchange of the diffusing particles (pure 1D diffusion). It is aimed at rationalizing the instability observed in the original DLA model in 2D. Using tabulated probabilities for attachment/killing of the random walkers we obtain the velocity of the instability growth. Thus, beyond the initial stages the difference in the cluster sizes Δh grows as dΔh/dt=1-Δb/Δk where the birth radius is xmax + Δb, the killing radius is xmax + Δk, the time is measured in number of particles released per growing aggregate and xmax is the size of the bigger cluster.
Keywords: diffusion-limited aggregation (DLA), growth instability, birth and killing radii, tabulated probabilities
Khimiya. 23, 269-274 (2014) Author(s): Z. Kostova, M. Topashka-Ancheva:
Abstract.This memorial note is devoted to Botyu Botev (1919-2008) who was an eminent scientist and public figure in the fields of cytology, immunology and educational policy.
Keywords: Botyu Botev, scientific activity, biology, educational policy
Khimiya. 23, 275-290 (2014) Author(s): M. Atanassova, R. Angelov:
Abstract.The discovery of chemical elements during the centuries from Antiquity up to now was observed in chemical and political point of view. A special attention was spared for the French chemists and the work of Marie Curie.
Keywords: chemical elements, history, discoveries