Semiempirical Quantum Chemical and Ab Intio Study of Co(Ii), Ni(Ii),Cu(Ii) and Zn(Ii) Complexes with the Azo Dye Derived from 4-Amino Antipyrine and 2,4-Dihydroxy Acetopheone

Semi-empirical quantum chemical calculation was made to study the nucleophilicity of the ligand and to study the mode of bonding between the ligand and the metal ions. The natural atomic charge at different atomic sites of the ligand has been calculated along with the electrostatic potential map to predict the reactive sites for electrophilic and nucleophilic attack. The theoretical spectral data such as IR, NMR and electronic have been calculated and compared with the experimentally generated data.

On the Sound, Produced by a Coin, Rolling in a Balloon

Balloons may be a thing children love playing with, but they also have different interesting physical properties such as the sound that is produced when something is put inside a balloon. The phenomenon of interest of this article is the one of gently rolling a coin in a balloon and exploration of the sound produced by this movement. It turns out that when a coin with edges is put in a balloon and is being rolled a buzzing sound is produced which varies in frequencies depending on the count of edges of the coin. This can be observed in non-laboratory conditions. Not many experiments have been conducted to explore this phenomenon.

Study of Compositions for Selective Water Isolation in Gas Wells

A hydrophobic composition containing water repellents and highly volatile solvents is shown in this study to isolate water from the bottomhole formation zone of gas wells and reduce as much as possible the saturation of pore spaces with water. During injection, this composition shows selectivity and mostly penetrates water-saturated porous media. The study shows that the injection of such composition into porous media has a high water-insulating effect, reducing the water permeability of water-saturated porous media by 35 times with a degree of water isolation of 97%. Moreover, while injecting, it has selective action, mainly penetrating water-saturated media rather than gas-saturated media. As a result of injecting 0.91 to 0.99 pore volumes (pv) of the composition, the Qwater/Qgas ratio reaches 5.22 to 5.26, indicating high selectivity.

Development of the Concept of Entropy: A Simpler Alternative to Carnot Cycle

The relationship between entropy and reversible heat and temperature is developed using a simple cycle, in which an ideal gas is subjected to isothermal expansion and compression and heated and cooled between states. The procedure is easily understood by students if they have knowledge of calculations involving internal energy, reversible work, and heat capacity for an ideal gas. This approach avoids the more time-consuming Carnot cycle. The treatment described here illustrates how the total entropy change resulting from an irreversible process is always positive.

Mutations and Variants of SARS-CoV-2, the Coronavirus Causing COVID-19

In 2020, the SARS-CoV-2 coronavirus caused a pandemic with severe consequences for many countries. The life cycle of the virus is briefly described. It is noted that the multiplication of viral genetic material is accompanied by the emergence of mutations, which leads to the emergence of new viral variants. Viral variants may differ in their effectiveness in infecting, spreading, in the severity of the disease they cause, and in their ability to escape acquired immunity. The most important SARS-CoV-2 variants that have emerged so far are discussed. The need for global monitoring of the emergence of new variants and rapid and mass vaccination to tackle the pandemic is emphasized.

Difficult Topics in the Chemistry Curriculum – Bulgarian Students‘ View

Chemistry is often considered a difficult subject, and the way students perceive learning affects their achievements. The research aims to identify: the topics in the secondary Chemistry curriculum perceived as difficult and as interesting by the Bulgarian students, the reasons for students’ difficulties and ways to overcome it. An inquiry was conducted with 321 students aged 16 – 17 years. According to them, the most difficult topics are Organic Chemistry and Chemical calculations (abstract and requiring specific skills). The most interesting topics are Organic Chemistry and Theory of Electrolytic Dissociation. Acids and bases. There is no significant correlation between levels of perceived difficulty and interest. Students relate difficulties to: information overload, emphasis on memorization, and lack of connections to everyday life. More lab activities and the practical application of the knowledge are recommended. Our research results can help improve Chemistry curricula and teaching practice.

From the Formation of the Earth to the Establishment of Luka

The article discusses successive stages in the evolution of life up to the establishment of the prokaryotic cell emphasizing the transitions from pre-biotic environment to organic precursors, pre-RNA-RNA, RNA-proteins-DNA, DNA-LUCA. They are paired with the development of pre-biotic structural progenitors of a cell - micelles, vesicles, protocells, prokaryotic ancestor, two prokaryotic branches – Eubacteria and Archaebacteria. The driving force is the natural selection (chemical, biochemical and biological), maintaining the correspondence between the emerging structures and their environment.

Potential Applications of Antibacteria in Edible Coating as Fish Preservative

Fish is a product that breaks down quickly due to biochemical reactions that cause a decrease in the quality of its nutritional and sensory values. Natural preservatives make fish safer for consumption than fish preserved with formalin. Edible coating is a preservative that can be eaten, can prevent biological, chemical and physical changes, is able to prevent mass transfer, acts as a moisture barrier, be contained antimicrobial/antibacterial and antioxidants, increases shelf life, as well as protects food from microbial contamination. Antimicrobial/antibacterial compounds added to edible coatings are able to inhibit food degradation and/or remodel toxic compounds such as free radicals. Antimicrobials can be obtained from plant extracts such as alkaloids, flavonoids, saponins, tannins, phenolic acids, and eugenol. These compounds can slow the growth of bacteria in fish namely Escherichia coli, Pseudomonas aeruginosa, Staphylococcus sp., Staphylococcus aureus, Psychrotrophic and Psychrophilic bacteria counts, Enterobacteriaceae, and lactic acid bacteria. This article reviews the application of various antibacterial compounds from various plants that are added to edible coatings as preservatives in fish.

Meteors – Basic Concepts and Terminology

This article discusses some basic concepts related to meteor astronomy, as well as the use of the correct terminology when working in Bulgarian. Due to the huge volume of topics, this is the first part of an upcoming series that examines only the most general principles in meteor science. The article can serve the public observatories and similar structures related to the teaching of amateur astronomy (due to the lack of such literature in Bulgarian), and meteor phenomena will continue to attract the attention of a wide range of people, giving them mostly a strong, emotional impact!

1300 Years Since the Birth of Geber – Beginning and Foundation of Arabic Alchemy

Geber (Latinized name of Jabir ibn Hayyan (c. 721 – c. 815)) is among the most notable representatives of medieval chemistry. The article, dedicated to the 1300th anniversary of his birth, tries to depict his work as the beginning and groundwork for Arabic alchemy, also serving as a push for the formation of chemistry in the future. The article touches upon his life, characteristics, evaluation of his works, doubts about his identity and authorship. His influences are examined and his achievements in the area of metallurgy (sulfur-mercury theory, characterizing all known metals), knowledge of `secret` (stimulating the transmutation of metals) substances, mineral acids, salts, chemical processes and apparatus, his contributions to practical chemistry prove the broadness of his interests. His rational and practical approach is acknowledged and also his “outer” spiritualism present in the terminology inherited by the authors of Alexandria. The legacy he leaves – his authority, influence on the development of chemistry and followers – Arabic medical alchemists. In the conclusion his services to science and civilization are summarized.