Scientific Publications
SCIENTIFIC PUBLICATION IN THE FIELD "SEDIMENTATION":

Authors 
Dimo Khristozov, Kiril Kolikov, Georgi Krustev, Elena Peeva. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІ, 2010, p. 361369. 
Abstract 
In the paper we describe a method without drying which determines the percentage of dry matter in liquid dispersions. We derive formulae for volume mass density of the particles from the dispersion phase, for sedimentary stability et al.
Key words: liquid dispersion, dispersion phase, sedimentary stability. 

Authors 
Kiril Kolikov, Georgi Krustev. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІ, 2010, p. 378382. 
Abstract 
We offer a summarization of the Stokes’ Law for sedimentation of fluid dispersed systems with high concentration sedimenting in an alternating nonhomogeneous gravitational field or in a centrifugal field.
Key words: Stokes' law, dispersed system, sedimentation. 

Authors 
Kiril Kolikov, Georgy Krustev, Dimo Christozov, Elena Peeva. 
Publication 
20th Anniversary International Scientific Conference, 34 June 2010. 
Abstract 
In the proposed paper we describe a method which investigates liquid dispersions after establishment of ultimate (maximum) sediment and emergent in the conditions of homogeneous gravitational and centrifugal field. Two straight cylindrical cuvettes with different radii are used. It is made a system of two linear algebraic equations. After solving of this system the following are found: densities of the ultimate sediment and emergent of the investigated dispersion. After that are found else the masses of sediment and emergent and the mass of the free (disconnected) disperse medium, most frequently water or serum. We introduce another two nondimensional parameters in order to characterize the stability of liquid dispersions sedimentations at straight and inverse sedimentation.).
Key words: liquid dispersion, density, sediment, emergent, stability. 

Authors 
Kiril Kolikov, Dimo Christozov, Georgy Krustev, Radka Koleva. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІІ, 2011, p. 239245. 
Abstract 
In the paper we describe a algebraic method for determination of volume mass density of the components: ultimate sediment and emergence, and free disperse medium in liquid dispersions. To separate the components of the liquid dispersion, we use straight cylindrical cuvettes, placed in the conditions of a gravitational or centrifugal field. After establishment of separated parts, we measure the linear dimensions of these parts. By means of these dimensions, we compose a system of linear algebraic equations. After solution of this system we find the values of the densities. Through them can be determined the masses of the different components. We introduce also a dimensionless numerical scale for characterization and prediction of sedimentation stability of liquid dispersions in straight and/or reverse sedimentation.
Key words: volumetric mass density; straight/reverse sedimentation; sedimentary stability. 

Authors 
Kiril Kolikov, Dimo Christozov, Georgy Krustev, Radka Koleva. 
Publication 
Plovdiv, Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V.ХIІІ, 2011, p. 246255 
Abstract 
In this paper we describe an barycentric effect of unidirectional displacement of center of masses at sedimentation in liquid dispersions. This effect, founded by us, goes in each liquid dispersion, placed in a vessel, in the conditions of static homogeneous gravitational field, constant temperature and constant external pressure. The sedimentation can be direct, as well reverse. Based on this effect, we have created two barycentric devices, which describe in our work. These devices characterize by easy feasibility, high sensibility, availability of price and application. It is possible each type liquid dispersion to be tested, independently of transparence and color. Based on these barycentric investigations, we present a new definition for sedimentational stability.
Key words: Liquid dispersions, Sedimentation, Sedimentary stability, Barycentric method. 

Authors 
Kiril Kolikov, Georgy Krustev. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІ, 2010, p. 370373. 
Abstract 
In the present article is given the first barycentric (using the center of mass) way of determining the degree of nonequilibrium for the processes in classical thermodynamics.
Key words: center of mass, classical thermodynamics, nonequilibrium thermodynamic processes. 
SCIENTIFIC PUBLICATION IN THE FIELD "DETERMINING OF INACCURACIES":

Authors 
Kiril Kolikov, Georgi Krustev, Yordan Epitropov, Todor Mollov. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІ, 2010, p. 426428. 
Abstract 
In all measurement devices the determination of the zero value is done by calibration, so that the error of the device is minimal. Let’s the device is set to zero when it has considerable indication in the given range to widen the range. This zero is not adequate to the objective reality, but it is pseudozero, that can cause serious error in the device’s indication. Those errors are random inaccuracies of measurement.
Key words: resetting a device, random inaccuracy (error). 

Authors 
Kiril Kolikov, Georgi Krustev, Yordan Epitropov, Dimo Hristozov. 
Publication 
Chemometr Intell Lab, 2010, doi:10.1016/j.chemolab.2010.03.001 (1,940) 
Abstract 
In the following paper we present an easily applicable new method for the analytical representation of the maximum absolute inaccuracy (error) of an indirectly measurable variablef = f (x_{1}, x_{2},...,x_{n}) as a function of the maximum absolute inaccuracies (errors) of the directly measurable variables x_{1}, x_{2},...,x_{n}. Our new approach is more adequate for the objective reality. The gist of it is that in order to find the analytical form of the maximum absolute inaccuracy of the variable f we take for being fixed variables the statistical mean values of the modules of the moment velocities of alteration of f in respect of the variables x_{1}, x_{2},...,x_{n}, and the numerical value of the maximum absolute inaccuracy of the variable f is found using the statistical mean values of the absolute values of the absolute inaccuracies . Having this in mind we develop the theory of errors, which we will call with what we feel is a more precise term – theory of inaccuracies. We introduce some new terms – space of the absolute inaccuracy and stochastic plane of the absolute inaccuracy of f. We also define a sample plane of the ideal absolutely accurate experiment and using it we define a universal numerical characteristic – a dimensionless scale for evaluation of the quality (accuracy) of the experiment..
Key words: indirectly measurable variable; maximum absolute error; dimensionless scale. 

Authors 
Kiril Kolikov, Yordan Epitropov, Dimo Hristozov. 
Publication 
Proceedings of the Anniversary International Conference 1012.12.2010, Plovdiv, Bulgaria, p. 159  166. 
Abstract 
Let us have an indirectly measurable variable which is a function of directly measurable variables. In this survey we present the introduced by us method for analytical representation of its maximum absolute and relative inaccuracy as functions, respectively, of the maximum absolute and of the relative inaccuracies of the directly measurable variables. Our new approach consists of assuming for fixed variables the statistical mean values of the absolute values of the coefficients of influence, respectively, of the absolute and relative inaccuracies of the directly measurable variables in order to determine the analytical form of the maximum absolute and relative inaccuracies of an indirectly measurable variable. Moreover, we give a method for determining the numerical values of the maximum absolute and relative inaccuracies. We define a sample plane of the ideal perfectly accurate experiment and using it we give a universal numerical characteristic – a dimensionless scale for determining the quality (accuracy) of the experiment.
Key words: indirectly measurable variable, maximum absolute inaccuracy; maximum relative inaccuracy, dimensionless scale. 

Authors 
Kiril Kolikov, Georgi Krustev, Yordan Epitropov, Dimo Hristozov. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІІ, 2011, p. 256266. 
Abstract 
In the following paper we present an easily applicable new method for the analytical representation of the maximum relative inaccuracy (error) of an indirectly measurable variable f = f (x_{1}, x_{2},...,x_{n}) as a function of the maximum relative inaccuracies (errors) of the directly measurable variables x_{1}, x_{2},...,x_{n}. Our new approach is more adequate for the objective reality. The gist of it is that in order to find the analytical form of the maximum relative inaccuracy of the variable f we take for being fixed variables the statistical mean values of the modules of the coefficients of influence of the relative inaccuracies в f . The numerical value of the maximum relative inaccuracy of the variable f is found using the statistical mean values of the absolute values of the relative inaccuracies . Moreover, we look into functions which are continuous but are not differentiable in respect to certain arguments in some points. Having this in mind we develop the theory of errors, which we will call with what we feel is a more precise term – theory of inaccuracies. We introduce some new terms – space of the relative inaccuracy and plane of the relative inaccuracy of f . We also define a sample plane of the ideal absolutely accurate experiment and using it we define a universal numerical characteristic – a dimensionless scale for evaluation of the quality (accuracy) of the experiment.
Key words: indirectly measurable variable, maximum relative error, dimensionless scale. 

Authors 
Kiril Kolikov, Georgi Krastev, Yordan Epitropov. 
Publication 
Plovdiv, Scientific studies of USB  Plovdiv, S. B, Natural sciense and Humanities, V. ХIІІ, 2011, p. 267274. 
Abstract 
With every precise measurement of a variable it is necessary to point out the inaccuracy involved in the measurement. Thus in the experimental sciences fundamental application have the maximum absolute and maximum relative inaccuracies (errors). In the current paper we expand the classic theory of the inaccuracies aiming at gaining if needed additional information about the inaccuracy of the measurement. Namely, let f = f (x_{1}, x_{2},...,x_{n}) is an indirectly measurable variable which is a function of the measurable variables x_{1}, x_{2},...,x_{n}. If in order to determine f several series of experimental measurements of x_{1}, x_{2},...,x_{n} have been carried out and the numerical values of f are different but the corresponding numerical values of the maximum absolute or of the maximum relative inaccuracies of f are equal by applying our method one can determine under which experiment the inaccuracy of the measurement is smaller.
Our new approach consists in introducing inaccuracies of second order and using them we represent the maximum absolute inaccuracy of second order as a quadratic form of the maximum absolute inaccuracies , and the maximum relative inaccuracy of second order as a quadratic form of the maximum relative inaccuracies. The numerical value of the maximum absolute inaccuracy of second order is determined by the statistical mean values of the absolute values of the absolute inaccuracies , and the numerical values of the maximum relative inaccuracy of second order is determined by the statistical mean values of the absolute values of the relative inaccuracies . Moreover, we examine functions which are continuous but are not differentiable in respect to some arguments in some points.
Key words: indirectly measurable variable, maximum absolute inaccuracy (error), maximum relative inaccuracy (error). 
SCIENTIFIC PUBLICATION IN THE FIELD "ELECTROSTATICS AND NUCLEAR FORCES":

Authors 
Kiril Kolikov 
Publication 
Kiril Kolikov. Electromagnetic nature of nuclear forces and the toroid structure of the helion and the alpha particle. Natural Science, 7, p. 484491, 2012. 
Abstract 
In the present paper, we consider the nucleons in the helium3 and helium4 nuclei as tori. These tori rotate with constant angular velocity around an axis, which is perpendicular to the rotation plane and passes through the centre of mass of the nuclei. Based on exact analytical expressions for the electrostatic interaction between two spheres with arbitrary radii and charges derived by us recently, we find that the wellknown potential binding energy for the helion and for the alpha particle is of electromagnetic character. Using the above mentioned formulae, we find the interaction force in the nuclei under consideration. Our toroid model recovers the basic experimental results not only for the binding energy, but also for the stability, radii, spins and the magnetic moments of the helion and the alpha particle.
Key words: Helion, Alpha particle, Strong interaction, Potential binding energy, Electrostatic interaction. 

Authors 
Kiril Kolikov, Dragia Ivanov, Georgi Krastev†, Yordan Epitropov, Stefan Bozhkov. 
Publication 
Kiril Kolikov, Dragia Ivanov, Georgi Krastev†, Yordan Epitropov, Stefan Bozhkov. Electrostatic interaction between two conducting spheres. Journal of Electrostatics, 70, p. 9196, 2012. 
Abstract 
In the paper we consider the problem of the electrostatic interaction between two charged conducting spheres with arbitrary electrical charges and radiuses. Using the image charges method we determine exact analytical formulas for the force F and for the potential energy W of the interaction between these two spheres as well as for the potential V of the electromagnetic field in an arbitrary point created by them. Our formulas lead to Coulomb’s law for point charges. We theoretically prove the experimentally shown fact that two spheres with the same type (positive or negative) of charges can also attract each other.
Key words: Conducting sphere; Coulomb's law; Image charges method; Electric interaction; Potential energy of electrostatic interaction; Potential of electrostatic field.


Authors 
Kiril Kolikov, Dragiya Ivanov, Georgi Krastev†. 
Publication 
Kiril Kolikov, Dragia Ivanov, Georgi Krastev†. Electromagnetic nature of the nuclear forces and a toroid model of nucleons in atomic nuclei. Natural Science, 1, p. 4756, 2012. 
Abstract 
In this paper we consider nucleons as tori, rotating with a constant angular velocity around the straight line passing through their mass centre (geometric centre) and perpendicular to their plane of rotation. We theoretically determine the corresponding potential energy and the force of interaction between pairs of nucleons, using our precise analytical formulas for the electrostatic interaction between two spheres with arbitrary radii and charges, which we derive using experimentally obtained results for the radii and the masses of the nucleons. From the values for binding energy found through our method, it follows that nuclear forces are electromagnetic in nature. In terms of magnitude of the force of interaction between proton and neutron, we obtain that Coulomb's forces are shortrange. Our toroid model explains the experimental results not only for binding energy, but also for the radius, magnetic moment and the spin of the nuclei of atoms.
Key words: Strong Interaction; Nucleon; Binding Potential Energy; Electromagnetic Interaction. 

Authors 
Kiril Kolikov, Dragiya Ivanov, Georgi Krastev†. 
Publication 
Kiril Kolikov, Dragia Ivanov, Georgi Krastev†. Electromagnetic nature of the nuclear forces and toroid structure of the deuteron and triton. Natural Science, 2, p. 123130, 2012. 
Abstract 
In this paper we model in a new way the nuclei of deuterium and tritium. We consider the nucleons as toroids that rotate at a constant angular velocity around an axis perpendicular to their rotation plane and passing through the center of mass of the nuclei. Based on exact analytical formulas obtained by us for the electrostatic interaction between two spheres with arbitrary radii and charges, we obtain that the known binding energy of the deuteron and triton has an electromagnetic nature. We also obtain through these formulas the force of interaction inside these nuclei. Besides that, within the framework of the classical model we use, we calculate the volumes and mass densities of the nucleons. Throughout all that we use the experimentally obtained results for the radii and masses of the nucleons and nuclei under study. Through our toroid model we confirm the main experimental results obtained for the deuteron and triton not only for the binding energy but also for the magnetic moments, spins and stability.
Key words: deuteron, triton, strong interactions, binding energy, electrostatic interactions. 
SCIENTIFIC PUBLICATION IN THE FIELD "BIOCHEMICAL STUDIES":

Authors 
Vanya Bogoeva, Lidiya Petrova, Ivan Ivanov, Hristina Kulina George Russev 
Publication 
Vanya Bogoeva, Lidiya Petrova, Ivan Ivanov, Hristina Kulina and George Russev. Interaction of wheat germ agglutinin with porphyrin compounds – potential anticancer agents, Biotechnology & Biotechnological Equipment (IF 0.29), 25, 3, 2011. 
Abstract 
Wheat germ agglutinin (WGA) is the first studied plant lectin shown to bind more strongly to tumour cells than to normal ones. WGA interacts with prostate cancer cells, human pancreatic cells and coloncancer cells.
Our results showed the interaction of WGA with two porphyrin compounds – Fe porphyrin and Pd porphyrin. The dissociation constants for the porphyrin binding was kD (0.081.02 µM) showing high affinity for the two porphyrins for this protein. The hyperbolic titration curve indicated the presence of a single porphyrin binding site.
In conclusion, we show that two photosentisizers with anticancer activity Fe porphyrin and Pd porphyrin, have high affinity for WGA. Since WGA binds to cancer cells, the results suggest that it may have utility in the targeted delivery of drugs for cancer.


Authors 
Vanya Bogoeva, Ivan Ivanov, Hristina Kulina, George Russev, Lybomira Atanasova 
Publication 
Vanya Bogoeva, Ivan Ivanov, Hristina Kulina, George Russev and Lybomira Atanasova. A novel cytokininbinding property of mistletoe lectin I from viscum album, Biotechnol. & Biotechnol. Eq. 2013, 27(1), 35833585. 
Abstract 
Lectins are proteins known for their ability to recognize and bind specific carbohydrates. In addition to their carbohydratebinding sites, some lectins possess hydrophobic sites and binding pockets capable of accommodating ligands such as phytohormones. Using the fluorescence spectroscopy method, we studied the interaction of mistletoe lectin I (MLI, from Viscum album) with hormones from the cytokinin group such as N6isopentenyladenine, zeatin, kinetin, and N6benzylaminopurine. Our results demonstrated that MLI binds to the studied cytokinins with high affinity (Kd = 0.7–1.7 μM). The interaction of MLI with the phytohormones causes conformational rearrangements within the protein and significant fluorescence increase (up to 40%) upon ligand binding. The hyperbolic titration curves as well as the comparable binding affinities indicate that the cytokinins could accommodate the same binding site. This is the first spectroscopic study demonstrating the novel property of mistletoe lectin to bind several cytokinins. Due to the high affinity to phytohormones, MLI could be related to the group of phytohormone(cytokinin)binding proteins. 

Authors 
Lidiya Petrova, Hristina Kulina, Anton Trifonov, George Russev, Kristiana Marinova and Vanya Bogoeva 
Publication 
Lidiya Petrova, Hristina Kulina, Anton Trifonov, George Russev, Kristiana Marinova and Vanya Bogoeva. Binding of antitumor compounds to wheat protein, Biotechnol. & Biotechnol. Eq. 27(3), 3857  3860 (2013). 
Abstract 
Binding of porphyrins to biological macromolecules is important to be studied as an approach to keeping them in stable, effective and safe dosage forms. In this work we show the interaction of three porphyrin compounds: Hematoporphyrin IX, Mn and Feporphyrins with plant lectin Wheat germ agglutinin (WGA). Porphyrin binding to WGA was monitored by the changes in the intrinsic protein fluorescence. Conformational changes due to the formation of WGAporphyrin complexes, were shown by the hyperbolic binding curves. The calculated dissociation constants KD (0.16 μМ to 0.24 μМ) indicate high affinity of WGA for the three porphyrins. Most probably they occupy the same high affinity sites. In conclusion, since WGA binds cancer cells and interacts with antitumor compounds, it could be useful as a drug delivery molecule. 
SCIENTIFIC PUBLICATION IN THE FIELD "PHYSICOCHEMICAL STUDIES":

Authors 
Ivan Minkov, Emil Manev, Svetla Sazdanova, Kiril Kolikov 
Publication 
Minkov, E. Manev, S. Sazdanova, K. Kolikov, Tests of the modified device for studying osmotic processes. Analysis of the results obtained at varied experimental conditions, Sci. Works (conference proceedings), Union of the Scientists in Bulgaria, Section Plovdiv, SeriesB. Natural Sciences and the Humanities Vol.XIII, ISSN 13119192, 2012, pp. 97100. 
Abstract 
Osmotic processes in aqueous solutions of sucrose was studied under varied experimental conditions: constant and variable solution volume; different concentrations (0.05 – 0.3 mil/L) and temperatures (22 – 42oC). The obtained experimental dependences are juxtaposed with the theoretical calculations through the socalled “van’t Hoff Law”


Authors 
Ivan Minkov, Georgi Krustev, Emil Manev, Kiril Kolikov 
Publication 
Minkov, G. Krustev, E. Manev, K. Kolikov, Average hydrostatic pressure on smooth solid surfaces. Application to membrane osmometry, Sci. Works, Schumen Univ.( conference proceedings), Shumen University press, ISBN: 9789545776434, 2012, pp. 359367. 
Abstract 
Hydrostatic pressure is a universal physical parameter, related to numerous applications in science and industry. This work examines the average hydrostatic pressure exerted upon some frequent for the practice types of planar (rectangular and circular) and corresponding nonplanar smooth surfaces of solid bodies immersed in a homogeneous liquid. The results obtained here are applied for the estimation of the osmotic pressure in colloidal and low molecular substance solutions, using semipermeable membranes. Further on, the maximal absolute and relative errors in the calculation of the osmotic pressure are assessed for the different cases. We expect the results obtained in our work to be applicable in colloid science, molecular biology, medicine, etc.
Key words: hydrostatic pressure, osmotic pressure, liquid, solid surface. 

Authors 
Dilyana Ivanova, Jana Angarska and Emil Manev 
Publication 
D. Ivanova, Zh. Angarska, E. Manev. Disjoining pressure isotherms obtained by dynamic method for foam films stabilized by nonionic surfactants. Ann. Shumen Univ., Nat.Sci., Chemistry, Vol. XXII B1, pp.5261, 2013. 
Abstract 
The present study is an attempt to explain by an additional nonDLVO force the accelerated thinning of foam films at low concentrations of ndodecylß Dmaltoside and hexaethylene glycol monododecyl ether in the presence of 0.1M NaCl, than that predicted by the Reynolds law. For its evaluation П(h) isotherms were obtained based on experimental dynamic thinning curves.
Keywords: foam film, disjoining pressure, film thinning. 

Authors 
Ivan Minkov, Emil Manev, Svetla Sazdanova, Kiril Kolikov 
Publication 
Minkov, E. Manev, S. Sazdanova, K. Kolikov. Influence of the experimental conditions on the osmotic pressure in aqueous solutions. Ann. Shumen Univ., Nat.Sci., Chemistry, Vol. XXII B1, pp.1727, 2013. 
Abstract 
Kinetics of the osmotic process in aqueous sucrose solutions was studied at two different regimes (constant and variable solution volume) in a wide range of solute concentrations: 0.02 – 1.0 mol/L. The obtained experimental dependences are in agreement with the expected acceleration of the osmosis upon raising the solute concentration. Yet, they reveal striking divergence in the rates of the process at constant and variable solution volume. The rise of pressure is much slower at variable volume, although the osmotic process occurs at a markedly faster rate of solvent influx.
Keywords: osmosis, osmotic pressure, kinetic of osmosis. 

