University of Chemical Technology and Metallurgy

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2-Alkyl-Substituted-4-Amino-Thieno[2,3-d]Pyrimidines: Anti-Proliferative Properties to In Vitro Breast Cancer Models
(2023-09-01) Iliev I.; Mavrova A.; Yancheva D.; Dimov S.; Staneva G.; Nesheva A.; Tsoneva I.; Nikolova B.
Thienopyrimidines are structural analogs of quinazolines, and the creation of new 2-alkyl derivatives of ethyl 4-aminothienopyrimidine-6-carboxylates for the study of their anti-proliferative properties is of great pharmacological interest. Some 2-alkyl-4-amino-thieno[2,3-d]pyrimidines 2–5 were synthesized, and their cyto- and phototoxicity against BALB 3T3 cells were established by an in vitro 3T3 NRU test. The obtained results indicate that the tested compounds are not cytotoxic or phototoxic, and that they are appropriate to be studied for their anti-proliferative and anti-tumor properties. The anti-proliferative potential of the compounds was investigated on MCF-7 and MDA-MB-231 cancer cells, as well as a MCF-10A cell line (normal human mammary epithelial cells). The most toxic to MCF-7 was thienopyrimidine 3 with IC50 13.42 μg/mL (IC50 0.045 μM), followed by compound 4 (IC50 28.89 μg/mL or IC50 0.11 μM). The thienopyrimidine 4 revealed higher selectivity to MCF-7 and lower activity (IC50 367 μg/mL i.e., 1.4 μM) than compound 3 with MCF-10A cells. With respect to MDA-MB-231 cells, ester 2 manifested the highest effect with IC50 52.56 μg/mL (IC50 0.16 μM), and 2-ethyl derivative 4 revealed IC50 62.86 μg/mL (IC50 0.24 μM). It was estimated that the effect of the substances on the cell cycle progression was due to cell cycle arrest in the G2 stage for MDA-MB-231, while arrest in G1 was detected for the estrogen (ER)-positive MCF-7 cell line. The tested compound’s effects on the change of the zeta potential in the tumorigenic cells utilized in this study were determined. The calculation which we performed of the physicochemical properties and pharmacokinetic parameters influencing the biological activity suggested high intestinal absorption, as well as drug-likeness.
21st European Conference on Fracture
(2018-01-01) Susmel L.; Carpinteri A.; Hattingh D.G.; Bozic Z.; Angelova D.
3D SPACE KINEMATICS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY
(2024-01-01) Slavov V.; Aleksandrova V.
This paper presents the main results of a study on the kinematics in 3D space of a robot used for process automation in metallurgy. The robot is studied as a mechanical system with twelve degrees of freedom consisting of seven rigid bodies. The transition matrices between the local and reference coordinate systems are defined in symbolic form. The position vectors and linear velocities of characteristic points are also defined in symbolic form as well as angular velocities of bodies from the mechanical system. A calculation algorithm is compiled and entered into a standard mathematical software product. Results are obtained in symbolic form and are valid for all mechanical systems with an analogous dynamic model. The kinematics results represent a basis for studying the dynamics and vibrations of a robot for automating processes in metallurgy.
5-Arylisothiazol-3(2H)-one-1,(1)-(di)oxides: A new class of selective tumor-associated carbonic anhydrases (hCA IX and XII) inhibitors
(2019-08-01) Cornelio B.; Laronze-Cochard M.; Miambo R.; De Grandis M.; Riccioni R.; Borisova B.; Dontchev D.; Machado C.; Ceruso M.; Fontana A.; Supuran C.T.; Sapi J.
Sixteen 5-aryl-substituted isothiazol-3(2H)-one-1,(1)-(di)oxide analogs have been prepared from the corresponding 5-chloroisothiazol-3(2H)-one-1-oxide or −1,1-dioxide by a Suzuki-Miyaura cross-coupling reaction and screened for their inhibition potency against four human carbonic anhydrase isoenzymes: the transmembrane tumor-associated hCA IX and XII and the cytosolic off-target hCA I and II. Most of the synthesized derivatives inhibited hCA IX and XII isoforms in nanomolar range, whereas remained inactive or modestly active against both hCA I and II isoenzymes. In the N-tert-butylisothiazolone series, the 5-phenyl-substituted analog (1a) excelled in the inhibition of tumor-associated hCA IX and XII (Ki = 4.5 and Ki = 4.3 nM, respectively) with excellent selectivity against off target hCA I and II isoenzymes (S > 2222 and S > 2325, respectively). Since the highest inhibition activities were observed with N-tert-butyl derivatives, lacking a zinc-binding group, we suppose to have a new binding mode situated out of the active site. Additionally, three free-NH containing analogs (3a, 4a, 3i) have also been prepared in order to study the impact of free-NH containing N-acyl-sulfinamide- (-SO-NH-CO-) or N-acyl-sulfonamide-type (-SO2-NH-CO-) derivatives on the inhibitory potency and selectivity. Screening experiments evidenced 5-phenylisothiazol-3(2H)-one-1,1-dioxide (4a), the closest saccharin analog, to be the most active derivative with inhibition constants of Ki = 40.3 nM and Ki = 9.6 nM against hCA IX and hCA XII, respectively. The promising biological results support the high potential of 5-arylisothiazolinone-1,(1)-(di)oxides to be exploited for the design of potent and cancer-selective carbonic anhydrase inhibitors.
6-(Propan-2-yl)-3-methyl-morpholine-2,5-dione, a novel cyclodidepsipeptide with modulatory effect on rat thymocytes
(2012-09-01) Pavlovic V.; Cherneva E.; Yancheva D.; Smelcerovic A.
A study has been carried out on the potential effect of a novel cyclodidepsipeptide, 6-(propan-2-yl)-3-methyl-morpholine-2,5-dione (PMMD), on rat thymocytes. Rat thymocytes were cultivated with increasing PMMD concentrations (0.1, 1, 10 μg/well), for 24. h, and evaluated for proliferative activity, viability, reactive oxygen species and mitochondrial membrane potential. The higher PMMD concentrations inhibited thymocytes proliferative activity mainly through induction of oxidative stress and resulting cytotoxicity, without any mitochondrial membrane potential alterations in thymocytes. The obtained results are correlated with previously published data on effects of 6-(propan-2-yl)-4-methyl-morpholine-2,5-diones on rat thymocytes. The presence of methyl group in position 4 or/and the length of alkyl chain in position 3 of 6-(propan-2-yl)-morpholine-2,5-dione core plays a role for the obtained differences in the biological response between PMMD and two previously tested 6-(propan-2-yl)-4-methyl-morpholine-2,5-diones. © 2012 Elsevier Ltd.
8-(Pyridin-2-yl)quinolin-7-ol as a platform for conjugated proton cranes: A dft structural design
(2020-10-01) Georgiev A.; Antonov L.
Theoretical design of conjugated proton cranes, based on 7-hydroxyquinoline as a tautomeric sub-unit, has been attempted by using ground and excited state density functional theory (DFT) calculations in various environments. The proton crane action request existence of a single enol tautomer in ground state, which under excitation goes to the excited keto tautomer through a series of consecutive excited-state intramolecular proton transfer (ESIPT) steps with the participation of the crane sub-unit. A series of substituted pyridines was used as crane sub-units and the corresponding donor-acceptor interactions were evaluated. The results suggest that the introduction of strong electron donor substituents in the pyridine ring creates optimal conditions for 8-(pyridin-2-yl)quinolin-7-ols to act as proton cranes.
A Chisel Fertilizer for In-Soil Tree-Layer Site-Specific Application in Precision Farming
(2023-01-01) Nukeshev S.; Yeskhozhin K.; Karaivanov D.; Ramaniuk M.; Akhmetov E.; Saktaganov B.; Tanbayev K.
An original technical solution is proposed that permits the application of a main fertilizer dose once in 4-5 years at a depth of 6-25 cm with an inclined belt. The work aims to investigate the interaction between the proposed working tool (ripper-distributor) of the developed chisel-fertilizer with the soil, and to determine dependences that link its traction force with the design parameters. Studying the soil deformation pattern under the influence of working tool cutting parts based on classical mechanics made it possible to determine the dependence between the tractive force of the ripper-distributor and its design parameters. 3D modeling and C.F.D. analysis by using SolidWorks Flow Simulation® made it possible to define the fertilizer distributor parameters of the working body and flow characteristics of fertilizers. The distribution quality studies of fertilizer granules in compartments of the working tool distributor showed that the non-uniformity of distribution at different dosages (from 50 to 400 kg/ha) ranges from 7.8% for the application of granulated superphosphate up to 22.7% for the application of powdered superphosphate. The chisel-fertilizer enables soil-friendly and sloping site-specific fertilizer application at a depth from 5.6-9.8, 16-18, 23-25.8 cm, and a fertilizer distribution non-uniformity of 14-15% over the width of the spreader.
A Comparative Azeotropic Research on Combustion of Common Ternary Systems
(2023-01-01) Abdelhafiz M.; Hussein A.K.; Naeim I.; Shalaby A.; Azazy A.; Saleh A.; Tolba S.; Elbeih A.
Methyl Tertiary Butyl Ether (MTBE) and Methanol are effective fuel oxygenate that boost octane number, improve fuel performance, combustion behavior and minimize environmental pollutant emissions. In the petroleum business, however, their high-water solubility restricts their use in terms of fuel homogeneity loss. This work presents a full investigation map for the status of the phase diagram for the tertiary system of MTBE-methanol-water at different temperatures; 0, 40, and 70oC, and different pressures; 1.0 and 3.0 atm, based on different compositions. Furthermore, the thermodynamic coefficient, UNIFAC-LL, was linked to the Aspen plus Version 9. After validation of the software by the real experimental data, the software was used to complete the full map at all missing conditions. Pressure does not influence the occurrence of phase transitions, but the temperature has a minor effect on the LLE. The methanol concentration at which phase separation occurred dropped from 43% to 31.2% when the temperature was lowered from 70 to 40°C. With the use of simulation, the compositions at which phase separation occurs were also discovered. Last but not least, it was observed that the thermodynamic model (UNIFAC-LL) properly predicted the behavior of the methanol-water-MTBE ternary system with less than 3% inaccuracy in the binodal curve points. Consequently, a validated phase diagram is developed to accurately predict the physical state of the MTBE-methanol-water system at ant temperature, pressure, and mole fraction of each component. Hence, it guarantees the feasibility of using this tertiary system, as an effective octane booster additive, under severe working conditions.
A comparative study on tribological behavior between metal and polymeric composites used to repair bronze made parts in dry reciprocating sliding tests
(2017-03-01) Iliuţǎ V.; Ripǎ M.; Javorova J.; Andrei G.
The paper presents the researches on tribological behaviour of two materials used for parts subjected to friction, under dry sliding conditions. The composite material is a product of the company Diamant Metallplastic GmbH, Germany and the manufacturer recommend it for repairing or reconditioning worn or damaged bronze made parts. The material belongs to Multimetall category, which is a highly resistant 2-component repair system. This polymer composite material was tribologically tested in dry friction reciprocating conditions, in ball-on-flat configuration, using the tribometer UMT-2 (Bruker, former CETR). The counterpiece was a steel ball. Typical test conditions were as follows: normal loads of 20, 30, 40 and 50 N, sliding distance of 100 m, stroke length of 5mm, average sliding speed of 3,5 mm/s, room temperature and relative humidity of 50-60%. After testing, wear tracks were examined by electronic microscopy (SEM), laser profilometry and the profilometric module of the tribometer CETR-UMT-2. The results of the composite material analysis were compared with the similar ones obtained under similar test conditions for the bronze (metal material).
A Computational approach to explicit feedback stochastic nonlinear model predictive control
(2010-01-01) Grancharova A.; Johansen T.A.
Nonlinear Model Predictive Control (NMPC) involves the solution at each sampling instant of a finite horizon optimal control problem subject to nonlinear system dynamics, and state and input constraints. Mathematical models of engineering systems usually contain some amount of uncertainty. In the robust NMPC problem formulation, the model uncertainty is taken into account. This paper presents an approximate multi-parametric Nonlinear Programming approach to explicit solution of feedback stochastic MPC problems for constrained nonlinear systems in the presence of stochastic uncertainty. It is assumed that the discrete probability distribution of the uncertainty is known. The mathematical expectation of the cost function is minimized subject to state and input constraints. The approximate explicit approach constructs a piecewise nonlinear approximation to the optimal sequence of feedback control policies. It is demonstrated by explicit feedback stochastic NMPC for a cart moving on a plane and attached to the wall via a spring. ©2010 IEEE.
A COMPUTER SIMULATION OF A BIOMASS GASIFICATION PROCESS
(2020-01-01) Chilev C.; Simeonov E.; Stoyanov V.; Chaushev S.
The biomass is one of the promising energy sources of the future. It is possible to use its energy potential through thermo-chemical conversion processes of pyrolysis and gasification. A particular attention has been recently paid to biomass gasification. Several models have been advanced to describe this complex process. The present communication suggests a flowsheet simulating a wood biomass gasifier. The simulations are carried out by ASPEN PLUS V.8.0 commercial software. The thermo-chemical models assume that the reactants reach a chemical equilibrium. The flowsheet includes three stages: raw biomass drying, a gasification process and a products separation. The simulations provide to predict the final composition of the gas mixture produced by biomass gasification. Sensitivity analyses are performed to determine the effect of the pressure, the air flow, the moisture content, and the air stream enthalpy on the amounts of the gases produced.
A conjugate heat transfer in a fixed-bed ceramic regenerator for air conditioning applications
(2020-01-01) Penev A.; Tsokov L.; Penkova N.
A mathematical model of the conjugate heat transfer in ceramic regenerative heat exchangers aiming a heat recovery in air conditioning systems is elaborated. The transient thermal and fluid flow fields in such a regenerator are obtained via numerical solutions by the finite volume method. The models are validated by comparing the computed and measured outlet temperatures and the heat transfer coefficients obtained by the simulations and the theory of similarity. The results related to the heat transfer and the thermal efficiency of the regenerator are discussed.
A correlation between structural and vibrational spectroscopic data of some beryllium sulfates and selenates (review)
(2016-01-01) Karadjova V.
The present paper summarizes experimental results on the study of some beryllium compounds and is a part of a dissertation entitled ``Synthesis, structure and properties of some beryllium salts - sulfates and selenates``. The solubility diagrams of the three-component systems BeSeO4-K2SeO4-H2O, BeSO4-Rb2SO4-H2O, and BeSeO4-MSeO4-H2O (M = Co, Ni, Cu, Zn) at 25°C are presented and the crystallization field widths of the solid phases are determined. The experimental results are discussed with respect to the complex formation processes in the ternary solutions and the solubility of the salt components in their binary solutions. New compounds, Rb2Be(SO4)2·2H2O and K2Be(SeO4)2·2H2O, have been obtained as a result of co-crystallization processes in the systems pointed above. The crystal structures of BeSeO4·4H2O, M2Be(SO4)2·2H2O (M = K, Rb), and K2Be(SeO4)2·2H2O are determined from single crystal X-ray diffraction data. It has been established that the beryllium selenate tetrahydrate crystallizes in the orthorhombic space group Cmca (D18 2h). The double beryllium compounds are isostructural and crystallize in the monoclinic space group P21/c (C52h). Vibrational (infrared and Raman) spectra are recorded in the regions of the normal vibrations of the different motives building up the structures of the beryllium compounds studied. The vibrational spectra are discussed in the light of both the crystal structures of the beryllium salts and the chemical properties of the different entities. Special attention is paid to the influence of different crystal chemical factors on the strength of the hydrogen bonds formed in the beryllium compounds. These are the Be-O interactions (synergetic effect), the proton acceptor capacity of the selenate and sulfate ions, the proton acceptor capacity of the different oxygen atoms as determined according to the Brown's bond valence theory, the compositions of the beryllium tetrahedra (acidity of the water molecules), the anti-cooperative effect (proton donor and proton acceptor competitive effect), the repulsion potential of the lattice sites of water molecules location, the size of M+ cations. The intramolecular O-H bond distances are derived from the νOD vs. rOD correlation curve [H.D. Lutz, C. Jung, J. Mol. Struct., 404, 1997, 63-66]. Water librations of protiated and deuterated samples are also discussed. Crystal matrix infrared spectroscopy was applied to analyze: (i) the distribution of SO42- ions included in the structure of K2Be(SeO4)2·2H2O at two crystallographically different positions; (ii) the molecular symmetry of SeO42- ions in BeSeO4·4H2O determined from the vibrational behavior of matrix-isolated SO42- guest ions; (iii) the strength of the hydrogen bonds (with the application of the isotopic dilution method and that of the matrix-isolated HDO molecules).
A correlation between the kinetic and thermodynamic adsorption characteristics of an optical brightener on a pulp surface
(2008-01-01) Radeva G.; Veleva S.; Valcheva E.
An attempt to find a correlation between the kinetic and thermodynamic terms (e.g. activation energy, pre-exponential factor, isosteric heat, entropy, etc.) of the chemisorption process involved in a commercial optical brightener/pulp system is presented. A linear inter-relationship between the kinetic and thermodynamic characteristics of the system was found. Based on the coefficients obtained in the thermodynamic investigation of the adsorption process, it was possible to calculate the kinetic coefficient of the surface inhomogeneity. The use of both a model employing uniformly inhomogeneous surfaces and an approach involving all the kinetic and thermodynamic data was confirmed by the results obtained.
A correlation method in studying chemisorption processes on uniformly inhomogeneous surfaces
(2010-03-01) Radeva G.; Valcheva E.; Veleva S.
Chemisorption processes taking place on uniformly inhomogeneous surfaces in the presence of entropic inhomogeneity are examined. A new form of linearity relationship connecting the current rate and the equilibrium constant at definite degrees of surface coverage is derived. The relationship can be applied to complex chemisorption processes when determination of the rate constant is impossible. Linear correlations between the activation energy and the adsorption enthalpy, as well as between the entropy characteristics and pre-exponential factors, are obtained. The complex effect of the energy and entropy factors on the kinetics and the equilibrium is discussed theoretically and verified experimentally. These factors operate through a thermodynamic and a kinetic compensation effect. The present paper illustrates the correlation methods employing experimental results derived from the study of the chemisorption of the optical brighteners Leucophor AP and Tinopal UP onto pulp, of Fe 3+ and Cu2+ ions onto fibrous polyampholyte and of hydrolysis-modified polyacrylonitrile (HMP) onto pulp.
A Coupled PDE-ODE Model for Nonlinear Transient Heat Transfer with Convection Heating at the Boundary: Numerical Solution by Implicit Time Discretization and Sequential Decoupling
(2023-04-01) Filipov S.M.; Hristov J.; Avdzhieva A.; Faragó I.
This article considers heat transfer in a solid body with temperature-dependent thermal conductivity that is in contact with a tank filled with liquid. The liquid in the tank is heated by hot liquid entering the tank through a pipe. Liquid at a lower temperature leaves the tank through another pipe. We propose a one-dimensional mathematical model that consists of a nonlinear PDE for the temperature along the solid body, coupled to a linear ODE for the temperature in the tank, the boundary and the initial conditions. All equations are converted into a dimensionless form reducing the input parameters to three dimensionless numbers and a dimensionless function. A steady-state analysis is performed. To solve the transient problem, a nontrivial numerical approach is proposed whereby the differential equations are first discretized in time. This reduces the problem to a sequence of nonlinear two-point boundary value problems (TPBVP) and a sequence of linear algebraic equations coupled to it. We show that knowing the temperature in the system at time level n − 1 allows us to decouple the TPBVP and the corresponding algebraic equation at time level n. Thus, starting from the initial conditions, the equations are decoupled and solved sequentially. The TPBVPs are solved by FDM with the Newtonian method.
A criterion to uniform stability for functional perturbed differential equations
(2016-01-01) Ahmad A.; Haider K.; Javad N.; Zeinev A.
In this paper we consider a class of non autonomous ODEs with a functional perturbation. For the unperturbed equation a Lyapunov function bounded by two quadratic forms is known. The Lipschitzean rate of the vector field along with some additional requirements to the derivatives of the Lyapunov function guarantee existence of uniform stable solutions. A sufficient condition that guarantees uniform stability of the zero-solution to the equation under consideration is discussed.
A cyber-physical approach for development of Vacuum Control System on the EBMR plant
(2023-01-01) Tzakova D.; Ivanova T.; Belev Y.; Batchkova I.
One of the great challenges of the Fourth Industrial Revolution is the transition to Cyber-Physical Systems, which allows for a high degree of adaptability, autonomy, reliability, usability and security. Cyber-Physical Systems-based control and automation is one of the possible ways to implement a smart factory. The cyber-physical approach, proposed in this paper is based on to the standard for Batch Control IEC-61512 (also known as S88) and the standard for development of distributed process measurement and control systems - IEC-61499. The suggested approach is implemented for development of vacuum control system, which is a part of the electron beam melting and refining plant producing metals and alloys with a high degree of purity.
A Flexible Miniature Antenna for Body-Worn Devices: Design and Transmission Performance
(2023-03-01) Al-Sehemi A.; Al-Ghamdi A.; Dishovsky N.; Atanasov N.; Atanasova G.
The last few years have seen a rapid increase in body-worn devices because these devices cover a broad spectrum of potential uses. Moreover, body-worn devices still require improvements in their flexibility, size, and weight that necessitate the development of flexible and miniature antennas. In this paper, we present a new flexible miniature antenna for body-worn devices. To ensure flexibility and comfort when the antenna is in contact with the human body, a substrate from natural rubber filled with TiO2 is developed. The miniaturization is achieved using the quadratic Koch curve. The antenna design, optimization, and characterization are performed on a human body model. The performance of the antenna is analyzed in two scenarios: (1) in- to on-body, and (2) on- to off-body wireless communications. The results show that the antenna realized the maximum telemetry range of more than 80 mm for in-body communications and more than 2 m for off-body communications. Moreover, the highest 10 g specific absorption rate value was 0.62 W/kg. These results, in addition to the antenna’s compact dimensions (12 mm × 26 mm × 2.5 mm) and the low manufacturing price, make the proposed antenna an ideal candidate for health telemetry applications.
A flexible planar antenna on multilayer rubber composite for wearable devices
(2017-01-01) Al-Sehemi A.; Al-Ghamdi A.; Dishovsky N.; Atanasova G.; Atanasov N.
This paper presents the design of a flexible antenna using planar dipole with a reflector to achieve optimal radiation efficiency and low specific absorption rate (SAR) when the antenna is placed directly over the skin of body model. The antenna is designed for the 2.45GHz frequency band. The parametric analysis of the proposed antenna is carried out. The proposed antenna achieves stable onbody performance: |S11| varies from −16.05 dB (on skin) at 2.47 GHz resonant frequency to −16.40 dB (in free space) at 2.44 GHz resonant frequency. It was found that the maximum 1 g average SAR value is only 0.23W/kg for an input power of 100mW when the antenna is placed directly over the skin of a three-layer body model, and radiation efficiency is 20.5%. The measured results are presented to demonstrate the validity of the proposed antenna.

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