Browsing by Author "Alexandrova R."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    A new cu(Ii) complex of pamam dendrimer modified with 1,8-naphthalimide: Antibacterial and anticancer activity
    (2022-08-15) Manov H.; Staneva D.; Vasileva-Tonkova E.; Kukeva R.; Stoyanov S.; Grabchev I.; Alexandrova R.; Stoyanova R.
    A new fluorescent PAMAM copper complex ([Cu2 (D)(NO3 )4 ]) has been synthesized and identified. The formation of the complex has been investigated by fluorescence spectroscopy which revealed two copper ions to be bound to the dendrimer ligand. That has also been confirmed upon subjecting the solid copper complex to electron paramagnetic spectroscopy. The antimicrobial activity of the copper complex against Gram-negative bacterium Pseudomonas aeruginosa in light and the dark has been studied. The results demonstrate an increase in its activity when irradiated with daylight. This activity of the copper complex is retained even after being loaded onto a cotton cloth. The antitumor activity of the copper complex and dendrimer ligand against triple-negative breast cancer MDA-MB-231 cells has been investigated as well.
  • No Thumbnail Available
    Item
    Balance modeling of the process for SiCaV alloy producing from waste vanadium catalyst
    (2014-02-25) Petrov P.; Marinov M.; Todorov P.; Alexandrova R.; Paunova R.
    The modern steel industry is characterized by continual improving the quality of the produced steel with constantly increasing range and quantity of deoxidation and alloying alloys. Among them falls SiCa with vanadium. Consider the absence in the Republic of Bulgaria of raw materials containing vanadium for example, the needs of metallurgy are provided mainly by imports of ferro-alloys. At the same time our country has an active chemical and metallurgical industries where significant polluting quantities of vanadium catalyst drop from production of sulfuric acid, which contains Si and V. Both material and heat balance models are developed for carbothermal producing of SiCa with a high content of vanadium. Vanadium waste, metallurgical lime and metallurgical coke are the raw material. The elements in the alloy after the carbothermal reduction are: V - 9.09 %, Fe - 9.06 %, Si - 66.45 %, Ca - 12.26 %, P - 0.02 %, S - 0.04 %, C - 0.21 %, Al - 2.83 % u Mn - 0.03 %. The main contributor into the alloy of V, Si and Fe is the waste vanadium catalyst. The relative consumption of electricity according to the heat balance model is 11505 kWh/ton alloy.
  • No Thumbnail Available
    Item
    Study on the behaviour of flotation fayalite waste from copper production at nonisothermal heating
    (2014-02-25) Alexandrova R.; Paunova R.; Marinov M.; Petrov P.
    The behaviour of flotation fayalite waste from copper slag at non-isothermal heating has been studied. Only a small part from this product (about 2 %) is used in the cement production. The other part, containing rather high percentage of iron is not used and it is deposited thus polluting the environment. DTA method was used to study the behavior of this waste at the non-isothermal heating up to 1273K and 1673K. Phase transformations have been defined by chemical and X-ray analyses. The phases of hematite, magnetite and cristalobalite were determined in the end product after flotation. Thermograms, obtained by DTA show that the oxidation processes run into two stages at the non-isothermal heating - the first stage up to T = 894K and the second one up to T = 1155K. Experimentally, the melting temperature of the flotation fayalite waste (Tmelt ≈ 1457K) was found. The melting of the sample in the crucible was observed at this temperature.
  • No Thumbnail Available
    Item
    Surface functionalization of cotton fabric with fluorescent dendrimers, spectral characterization, cytotoxicity, antimicrobial and antitumor activity
    (2019-06-01) Grabchev I.; Staneva D.; Vasileva-Tonkova E.; Alexandrova R.
    Poly(propylenimine) dendrimers from first and third generations modified with 1,8-naphthalimide units and their Zn(II) complexes have been investigated by absorption and fluorescence spectroscopy. These dendrimers have been deposited on a cotton cloth by the extraction method, producing yellow-colored textile materials. They have been characterized by defining their color coordinates L*a*b*, XYZ and xy. The antimicrobial activity of dendrimers has been investigated in vitro against model gram-positive and gram-negative bacteria and yeasts. Being deposited onto the surface of cotton fabric, the studied dendrimers reduced bacterial growth and prevented the formation of bacterial biofilm. Anticancer and cytotoxicity activities have also been performed against HeLa and Lep-3 human tumor cell lines as model systems.