Обучение по природни науки и върхови технологии

2015/6, стр. 877 - 890

PARALLEL STABILITY ANALYSIS OF MEMBRANE LAMELLAR STRICTURES AND FOAM FILMS

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Ключови думи:

90th Anniversary of the Department of Physical Chemistry of the University of Sofia Юбилей: 90 години на Катедрата по физикохимия на Софийския университет

Introduction

Thin liquid films (TLFs) bounded by simple interfaces, insoluble monolayers and membranes are in the scientific focus from many years (Scheludko, 1984). The interest to these nanothin structures is promoted by specific phenomena taking place in films and the large application in technology. An important aspect in the practical application is the stability of TLFs (Scheludko, 1967; Vrij & Overbeek, 1968; Derjaguin, 1986), which is decisive for many processes in flotation (Schulze, 1984), colloid coagulation (Chester, 1991), food industry (Patino et al., 1995), and in other disperse systems (Malysa & Warszynski, 1996). In the literature, the TLF stability is described as a result of competition between van der Waals disjoining pressure and stabilizing effect of capillary and electrostatic forces (DLVO theory). A linear hydrodynamic theory of the kinetics of hole or black spot formation is developed (Vrij, 1966; Jain et al., 1979; Radoev at al., 1983) which provides calculation of the film lifetime and critical thickness. This theory accounts for many interfacial processes such as adsorption, surface and bulk diffusion of surfactants, Marangoni effect, etc. The basic restriction of the linear theory is the small parameter expansion over the ratio between the amplitude z of the surface corrugations and the average film thickness h. Since on the point of the film rupture they are of equal order such presumption is not justified. However, the linear theory results are very important for interpretation of light scattering experiments (Young & Clark, 1981; Joosten, 1984; Meunier, 1987; Earnshaw & McGivern, 1989).

An interesting effect on the TLF stability is the coupling of the film drainage and the unstable modes due to non-linear TLF hydrodynamics (Sharma & Ruckenstein, 1987; Tsekov & Ruckenstein, 1993). Its theoretical description requires correct calculation of the drainage rate, which depends substantially by the shape of the film interfaces. Usually, a dimple is formed (Radoev et al., 1983; Ivanov et al., 1985; Joye et al., 1992; Tsekov & Ruckenstein, 1994; Velev et al., 1993) and the corresponding law of thinning (Manev et al., 1997; Tsekov, 1998) differs from the classical Reynolds expression applied first to TLF by A. Scheludko. During last decades, some attempts to take into account the influence of non-linear effects on TLF stability have been made. Some authors (Sharma & Ruckenstein, 1986; Prevost & Gallez, 1986; Yiantsios & Higgins, 1991) have reported analytical-numerical calculations based on the Navier-Stokes equations. These theories continue usual ideas of hydrodynamic stability without considering fluctuations. Other authors (Wu & Hwang, 1991) have accounted for the influence of the thermoconvection in a non-linear flow by means of temperature dependence of viscosity. The main non-linear effects are due to two factors: the non-linear hydrodynamic terms in the Navier-Stokes equations and the non-linear dependence of the disjoining pressure from the film thickness. In pure form, the first effect takes place at capillary-gravity waves on infinitely deep liquids where the disjoining pressure is missing. In this case, the interfacial kinematics is described by a Korteweg-de Vries equation of fifth degree (Boyd, 1991).

The dependence of the disjoining pressure from the film thickness is a problem, which has been object of intensive investigations. Abreast of now becoming classical van der Waals and electrostatic components, a number of new interesting effects of macroscopic interaction were observed (Israelashvili, 1991). Here we can mention non-DLVO hydrophobic, hydration, protrusion, etc., forces (Christenson, 1988). In the case of surfactant concentration above CMC the disjoining pressure isotherm exhibits periodic behavior, which is responsible for the film stratification (Bergeron & Radke, 1992). Similar periodic behavior but with smaller characteristic length could be expected as a consequence of the discrete molecular structure of the matter (Sarman, 1990).

The picture in membrane multi-lamellar structures is additionally complicated by the low value of surface tension leading to large out of plane deviations of membranes. For this reason, the steric interaction between the two membranes bordered the film becomes important and leads to the so-called undulation forces (Helfrich, 1978). This interaction depends substantially by the membrane elasticityκ , which can be conveniently measured by ellipsometry and X-ray scattering (Meunier, 1990; Meunier & Lee, 1991). Membranes are soft and easy flexible bilayer structures, which possess freedom for fluctuations into membrane plane (Cevc & March, 1987). The scale of these fluctuations grows up close to the intra-membrane phase transitions (Lemmich et al., 1994; Raudino, 1995). The mechanical properties of membranes, even if composed by two or more monolayers of insoluble surfactants, are far from those of the latter (Brochard et al., 1976; Bois & Panaiotov, 1995). The internal behavior of bilayers is well studied by means of methods based on diffraction and scattering of light (Kramer, 1971; Meunier & Henon, 1991), X-rays (Matuoka et al., 1994) and neutrons (Pfeiffer et al., 1993; Konig et al., 1994), and some interesting phase transitions are observed as result of the phase state of the lyophobic parts of surfactant molecules (Nagle, 1980; Ruggiero & Hudson, 1989). They play important role not only in the membrane transport, elastic properties and secondary quasi-crystalline arrangement of the membrane incorporations but also in the biological functions. Additional complications could arise from existence of membrane proteins, which interact each other by potential and curvature induced surface forces (Velev et al., 1993; Chandra & Safran, 1992; Kralchevsky et al., 1995). Due to the Brownian motion they migrate and create a secondary crystalline structure, which changes properties of the whole membrane (Careri, 1982). The problem of rupture of TLF bounded by biomembranes is relevant to coalescence of biological cells, fusion of colloids in cells, stability of vesicles and lamellar structures and other life important processes. Both linear (Ljunggren & Eriksson, 1991) and non-linear (Galez et al., 1993) theories were applied to the multilamellar membrane structure stability. A quasi-thermodynamic theory for rupture of bilayers and Newton black films was proposed (Kashchiev & Exerowa, 1980), which explains the phenomenon by appearance of holes with a critical size.

Fluctuations in thin liquid films

An important feature of fluctuations in fluids is the presence of collective hydrodynamic fluctuating modes (Forster, 1975; Balescu, 1975; Resibois & de Leener, 1997; Klimontovich, 1986). The local fluctuations of the TLF thickness are the major factor responsible for the film instability. Two types of modes exist in films with fluid interfaces, bending and squeezing modes, and the latter are responsible for the film rupture (Joosten, 1984; Haskell et al., 1993). The dynamic behavior of the squeezing modes is determined by the film disjoining pressure, surface tension and viscosity of the fluid (Ivanov, 1988; Ivanov & Dimitrov, 1974; Manev et al., 1976). The films rupture spontaneously at positive first derivative of the disjoining pressure. In the frames of the linear analysis, the pressure fluctuations can be expressed as a superposition of wave disturbances with different wave number and amplitude. It is known that asymmetric film disorders are the most destabilizing for films (Ivanov & Dimitrov, 1974). The effect of such surface waves is summarized in details in the paper of Narsimhan (2005).

According to TLF hydrodynamics the pressure acting on the film surfaces has the form

p = −(s / 2)Dz + (κ / 2)DDz − Π′z + d(1)P

The first term here represents the local capillary pressure, where s is the surface tension. The second term accounts for elastic deformations of the film surfaces with elasticity modulus k of the interfaces. is the first derivative in respect to h of the total disjoining pressure, being sum of all existing components, and dP represents the pressure fluctuations due to the thermal motion. In Fourier form the equation describing the thickness fluctuations reads (Ivanova & Tsekov, 2013):

(24η / q2h3 ) tz q + (sq2 + κq4 2Π′)z q = −2dP(2)q

where q represents the wave vector modulus. One can recognize now the destabilizing role of the negative components of the disjoining pressure on the film waves. They can lead to a negative harmonic force which is an indication for divergent solutions.

It is important to note the stabilizing effect of the surface tension and the film surface elasticity. It is possible to obtain from Eq. (2) the spatial spectral density of the thermal non-homogeneity of the film thickness (Horsthemke & Lefever, 1984):

Figure 3. Dependences of the lifetime on film thickness, viscosity and electrolyte concentration

232424Czz(q,t)=R2(s2qkB2T+κ4)2Πexp[(qh/122ηΠ)(2Πs−s2qκ4κq)t]−sqκqpqqq

The fundamental result (3) contains the well-known quantitative criterion for the film stability. It is easy to recognize that the thickness waves become unstable C(zz ) when the inequality 2Π> sq2 + κq4 is fulfilled. The corresponding equality defines a critical wave number

qcr = 2(8)/2s+κΠsκ

which the waves are not stable and their amplitudes grow exponentially. In the case of negligible elastic modulus k this criterion reduces to the well-known result qqforcrcr== .. The wave number of the most rapid FourieTheotherstructuresextremeandcasetheofcorrespondingnegligiblesurface criticalr mode istensionwave is numberappropriatereads

qmq = 2(6)/3s+κΠsκ

It is easy to show that the most rapid wave is unstable, since qmq < qcr . For the two cases discussed before the corresponding values of the wave numbers of the most rapid

waves are equal to qmq = Π/s and q mq = 4 23Π/κ, respectively.

The total disjoining pressure in the DLVO theory is a sum of the electrostatic and van der Waals components. The main parameter accounting for the specific interactions in films is the first derivative of the disjoining pressure

Π′ = 3KVW / h4 64CF 02/ABNkTCeeexp( 02/ABCNkTeeFh(6))

According to Fig. 1 there are two values of electrolyte concentration C, where the first derivative becomes zero. These lower and higher values correspond to maximum and minimum of the disjoining pressure, respectively. Unstable film possesses thickness smaller than that at the maximum at about C = 10 mM, where a transition from stable to unstable film occurs. In the present paper two models are discussed with different specific constants: the Model A is a film with fluid interphases and the Model B is a film separating two lipid membranes. In both cases the fluid in the film is water and therefore the standard values of the constants are: T = 300 K, e0e = 0.5 nF/m, KVW = 6.25 meV, h = 1 mPa s, h = 30 nm, R = 0.1 mm. The only difference in the two models is the elastic property of the interfacial boundary. A typical value of the surface tension of the Model A is s = 50 mN/m, while k º 0. In this case the wave number of the most rapid mode qmq is about 250 mm-1 and the critical wave number q cr is about 385 mm-1. For the Model B s º 0 and k = 0.5 pJ, and the wave number of the most rapid mode qmq is about 265 mm-1 and critical wave number qcr is about 345 mm-1.

Figure 1. The isotherm of Π

is presented for aqueous films

Rupture of thin liquid films

The process of film rupture occurs in two stages: formation of a hole and expansion of its area. The slow rate-determining step is the hole-formation (Scheludko, 1967; Derjaguin, 1984) and the film rupture can be defined by the appearance of the first hole in the film. It is known that small fluctuations of physical quantities are Gaussian (Horsthemke & Lefever, 1984). Therefore, the probability density for a local deviation from the average thickness of the film is given by the normal distribution

p(z,t) = exp(−z2 / 2A2 ) / 22Ap

To take into account that the film ruptures at the hole-formation, one must introduce an adsorption boundary at z = -h. Thus, one can derive an expression for the probability density for locale thickness fluctuations in the real unstable film

w(z ,t ) = [exp(−z 2 / 2A 2) exp( (z + 2h) 2 / 2A 2)] / 22Ap

From Eq. (8) one can estimate the total probability for the film to be alive until the time t, which is equal to the probability not to have a hole in the film in the presence of adsorption boundary

W (t ) = w (z,t )d z = erf(h / 2A(9) )

h

For unstable films W(¥) = 0 and one can calculate the average lifetime of the film t as follows

∞ ∞

t = td (1W ) =(10)Wdt

0 0

This lifetime depends on the amplitude A of the unstable waves and calculations are carried out numerically to discriminate the influence of different physical factors.

Let us consider first the influence of the elastic properties on the film lifetime (Fig. 2). The dependence of the critical value of the wave vector qcr for the Model A on the surface tension is the square root, while for the Model B the dependence of qmd on the elasticity module is the root of the square root. Hence, the lifetime of films in the Model A is stronger dependent on s than the dependence of t on k for films in the Model B. The surface elasticity in both cases suppresses the amplitude of the fluctuation waves and thus increases the film lifetime.

The dependences of the film lifetime on the film thickness, viscosity and electrolyte concentration, presented in Fig. 3 for both models, are similar. At large film thicknesses the disjoining pressure disappears and the probability of hole-formation tends to zero. This explains the observed increase of t at higher film thickness h. The role of viscosity is to delay the evolution of the waves due to the increase of friction inside the film, which naturally increases the film lifetime. As is seen that the lifetime increases also with increase of the electrolyte concentration since the larger surface charge density results in higher value of the stabilizing electrostatic component of the disjoining pressure. At sufficiently large concentrations the electrostatic component must be reduced due to shortening of the electric double layer thickness. This effect should reduce also the film lifetime but it is significant for concentrations outside the considered range of C. The trends of the lifetime of films formed between biological membranes (the Model B) are weaker than that for the Model A.

Figure 2. Influence of the surface tension and the elasticity modulus on the TLF lifetime

Generally, the film lifetime should not depend on the film radius for non-thinning films. The behavior of t(R) on Fig. 4 is analogous for the two considered models. There are obviously radii, at which the films are more stable due to the lack of standing waves with a wavelength equal to the most rapid one. When the most rapid wave is present in the wave spectrum, the film lifetime decreases significantly to a constant value. At larger radii this is always the case.

Conclusion

In the present paper two models of thin liquid films are discussed: the Model A for films bounded by classical interfaces and the Model B for films separating lipid bilayers. As a result of the theoretical consideration differences in the behavior of the two systems are discovered, due to the different power of the elastic responses of the films. The dependences of the film lifetime on various physical parameters such as the electrolyte concentration, surface tension, interfacial elasticity, viscosity and film thickness are examined. The dependence of the lifetime on the film radius is especially interesting due to the presence of ‘magic’ values, corresponding to sufficiently stable films.

Figure 4. Dependence of the film lifetime on the radius of the film

Acknowledgments. The present paper is dedicated to the 90th Anniversary of the Department of Physical Chemistry, University of Sofia. The authors are thankful to the FP7 Project BeyondEverest and to the Bulgarian NSF for a financial support through the Grant DRG 02/3.

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АНАЛИЗ НА ПРИРОДНИ ВОДИ В ОБЩИНА СЛИВЕН

Никола Урумов, Анелия Иванова

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Виктория Дечкова, Никола Велчев, Нели Иванова

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MATHEMATICAL MODELLING OF THE TRANSMISSION DYNAMICS OF PNEUMONIA AND MENINGITIS COINFECTION WITH VACCINATION

Deborah O. Daniel, Sefiu A. Onitilo, Omolade B. Benjamin, Ayoola A. Olasunkanmi

2024 година
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2023 година
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ПОДКАСТ – КОГА, АКО НЕ СЕГА?

Христо Чукурлиев

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2022 година
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METEOROLOGICAL DETERMINANTS OF COVID-19 DISEASE: A LITERATURE REVIEW

Z. Mateeva, E. Batchvarova, Z. Spasova, I. Ivanov, B. Kazakov, S. Matev, A. Simidchiev, A. Kitev

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MATHEMATICAL MODELLING OF THE TRANSMISSION MECHANISM OF PLAMODIUM FALCIPARUM

Onitilo S. A, Usman M. A., Daniel D. O. Odetunde O. S., Ogunwobi Z. O., Hammed F. A., Olubanwo O. O., Ajani A. S., Sanusi A. S., Haruna A. H.

ПОСТАНОВКА ЗА ИЗМЕРВАНЕ СКОРОСТТА НА ЗВУКА ВЪВ ВЪЗДУХ

Станислав Сланев, Хафизе Шабан, Шебнем Шабан, Анета Маринова

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MAGNETIC PROPERTIES

Sofija Blagojević, Lana Vujanović, Andreana Kovačević Ćurić

„TAP, TAP WATER“ QUANTUM TUNNELING DEMONSTRATION

Katarina Borković, Andreana Kovačević Ćurić

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КОМЕТИТЕ – I ЧАСТ

Пенчо Маркишки

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DISTANCE LEARNING: HOMEMADE COLLOIDAL SILVER

Ana Sofía Covarrubias-Montero, Jorge G. Ibanez

2021 година
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STUDY OF COMPOSITIONS FOR SELECTIVE WATER ISOLATION IN GAS WELLS

Al-Obaidi S.H., Hofmann M., Smirnov V.I., Khalaf F.H., Alwan H.H.

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POTENTIAL APPLICATIONS OF ANTIBACTERIAL COMPOUNDS IN EDIBLE COATING AS FISH PRESERVATIVE

Maulidan Firdaus, Desy Nila Rahmana, Diah Fitri Carolina, Nisrina Rahma Firdausi, Zulfaa Afiifah, Berlian Ayu Rismawati Sugiarto

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INVESTIGATION OF 238U, 234U AND 210PO CONTENT IN SELECTED BULGARIAN DRINKING WATER

Bozhidar Slavchev, Elena Geleva, Blagorodka Veleva, Hristo Protohristov, Lyuben Dobrev, Desislava Dimitrova, Vladimir Bashev, Dimitar Tonev

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DEMONSTRATION OF DAMPED ELECTRICAL OSCILLATIONS

Elena Grebenakova, Stojan Manolev

2020 година
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ДОЦ. Д-Р МАРЧЕЛ КОСТОВ КОСТОВ ЖИВОТ И ТВОРЧЕСТВО

Здравка Костова, Елена Георгиева

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JACOB’S LADDER FOR THE PHYSICS CLASSROOM

Kristijan Shishkoski, Vera Zoroska

КАЛЦИЙ, ФОСФОР И ДРУГИ ФАКТОРИ ЗА КОСТНО ЗДРАВЕ

Радка Томова, Светла Асенова, Павлина Косева

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MATHEMATICAL MODELING OF 2019 NOVEL CORONAVIRUS (2019 – NCOV) PANDEMIC IN NIGERIA

Sefiu A. Onitilo, Mustapha A. Usman, Olutunde S. Odetunde, Fatai A. Hammed, Zacheous O. Ogunwobi, Hammed A. Haruna, Deborah O. Daniel

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WATER PURIFICATION WITH LASER RADIATION

Lyubomir Lazov, Hristina Deneva, Galina Gencheva

2019 година
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LASER MICRO-PERFORATION AND FIELDS OF APPLICATION

Hristina Deneva, Lyubomir Lazov, Edmunds Teirumnieks

ПРОЦЕСЪТ ДИФУЗИЯ – ОСНОВА НА ДИАЛИЗАТА

Берна Сабит, Джемиле Дервиш, Мая Никова, Йорданка Енева

IN VITRO EVALUATION OF THE ANTIOXIDANT PROPERTIES OF OLIVE LEAF EXTRACTS – CAPSULES VERSUS POWDER

Hugo Saint-James, Gergana Bekova, Zhanina Guberkova, Nadya Hristova-Avakumova, Liliya Atanasova, Svobodan Alexandrov, Trayko Traykov, Vera Hadjimitova

Бележки върху нормативното осигуряване на оценяването в процеса

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ТЕХНОЛОГИЯ

Б. В. Тошев

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ON THE GENETIC TIES BETWEEN EUROPEAN NATIONS

Jordan Tabov, Nevena Sabeva-Koleva, Georgi Gachev

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CHEMOMETRIC ANALYSIS OF SCHOOL LIFE IN VARNA

Radka Tomova, Petinka Galcheva, Ivajlo Trajkov, Antoaneta Hineva, Stela Grigorova, Rumyana Slavova, Miglena Slavova

ЦИКЛИТЕ НА КРЕБС

Ивелин Кулев

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ПРИНЦИПИТЕ НА КАРИЕРНОТО РАЗВИТИЕ НА МЛАДИЯ УЧЕН

И. Панчева, М. Недялкова, С. Кирилова, П. Петков, В. Симеонов

UTILISATION OF THE STATIC EVANS METHOD TO MEASURE MAGNETIC SUSCEPTIBILITIES OF TRANSITION METAL ACETYLACETONATE COMPLEXES AS PART OF AN UNDERGRADUATE INORGANIC LABORATORY CLASS

Anton Dobzhenetskiy, Callum A. Gater, Alexander T. M. Wilcock, Stuart K. Langley, Rachel M. Brignall, David C. Williamson, Ryan E. Mewis

THE 100

Maria Atanassova, Radoslav Angelov

A TALE OF SEVEN SCIENTISTS

Scerri, E.R. (2016). A Tale of Seven Scientists and a New Philosophy of Science.

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DEVELOPMENT OF A LESSON PLAN ON THE TEACHING OF MODULE “WATER CONDUCTIVITY”

A. Thysiadou, S. Christoforidis, P. Giannakoudakis

AMPEROMETRIC NITRIC OXIDE SENSOR BASED ON MWCNT CHROMIUM(III) OXIDE NANOCOMPOSITE

Arsim Maloku, Epir Qeriqi, Liridon S. Berisha, Ilir Mazreku, Tahir Arbneshi, Kurt Kalcher

THE EFFECT OF AGING TIME ON Mg/Al HYDROTALCITES STRUCTURES

Eddy Heraldy, Triyono, Sri Juari Santosa, Karna Wijaya, Shogo Shimazu

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A CONTENT ANALYSIS OF THE RESULTS FROM THE STATE MATRICULATION EXAMINATION IN MATHEMATICS

Elena Karashtranova, Nikolay Karashtranov, Vladimir Vladimirov

SOME CONCEPTS FROM PROBABILITY AND STATISTICS AND OPPORTUNITIES TO INTEGRATE THEM IN TEACHING NATURAL SCIENCES

Elena Karashtranova, Nikolay Karashtranov, Nadezhda Borisova, Dafina Kostadinova

45. МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Василева

2018 година
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ЗДРАВЕ И ОКОЛНА СРЕДА

Кадрие Шукри, Светлана Великова, Едис Мехмед

РОБОТИКА ЗА НАЧИНАЕЩИ ЕНТУСИАСТИ

Даниела Узунова, Борис Велковски, Илко Симеонов, Владислав Шабански, Димитър Колев

DESIGN AND DOCKING STUDIES OF HIS-LEU ANALOGUES AS POTENTIOAL ACE INHIBITORS

Rumen Georgiev, , Tatyana Dzimbova, Atanas Chapkanov

X-RAY DIFFRACTION STUDY OF M 2 Zn(TeО3)2 (M - Na, K) ТELLURIDE

Kenzhebek T. Rustembekov, Mitko Stoev, Aitolkyn A. Toibek

CALIBRATION OF GC/MS METHOD FOR DETERMINATION OF PHTHALATES

N. Dineva, I. Givechev, D. Tanev, D. Danalev

ELECTROSYNTHESIS OF CADMIUM SELENIDE NANOPARTICLES WITH SIMULTANEOUS EXTRACTION INTO P-XYLENE

S. S. Fomanyuk, V. O. Smilyk, G. Y. Kolbasov, I. A. Rusetskyi, T. A. Mirnaya

БИОЛОГИЧЕН АСПЕКТ НА РЕКАНАЛИЗАЦИЯ С ВЕНОЗНА ТРОМБОЛИЗА

Мариела Филипова, Даниела Попова, Стоян Везенков

CHEMISTRY: BULGARIAN JOURNAL OF SCIENCE EDUCATION ПРИРОДНИТЕ НАУКИ В ОБРАЗОВАНИЕТО VOLUME 27 / ГОДИНА XXVII, 2018 ГОДИШНО СЪДЪРЖАНИЕ СТРАНИЦИ / PAGES КНИЖКА 1 / NUMBER 1: 1 – 152 КНИЖКА 2 / NUMBER 2: 153 – 312 КНИЖКА 3 / NUMBER 3: 313 – 472 КНИЖКА 4 / NUMBER 4: 473 – 632 КНИЖКА 5 / NUMBER 5: 633 – 792 КНИЖКА 6 / NUMBER 6: 793 – 952 КНИЖКА 1 / NUMBER 1: 1 – 152 КНИЖКА 2 / NUMBER 2: 153 – 312 КНИЖКА

(South Africa), A. Ali, M. Bashir (Pakistan) 266 – 278: j-j Coupled Atomic Terms for Nonequivalent Electrons of (n-1)fx and nd1 Configurations and Correlation with L-S Terms / P. L. Meena (India) 760 – 770: Methyl, тhe Smallest Alkyl Group with Stunning Effects / S. Moulay 771 – 776: The Fourth State of Matter / R. Tsekov

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ИМОБИЛИЗИРАНЕНАФРУКТОЗИЛТРАНСФЕРАЗА ВЪРХУКОМПОЗИТНИФИЛМИОТПОЛИМЛЕЧНА КИСЕЛИНА, КСАНТАН И ХИТОЗАН

Илия Илиев, Тонка Василева, Веселин Биволарски, Ася Виранева, Иван Бодуров, Мария Марудова, Теменужка Йовчева

ELECTRICAL IMPEDANCE SPECTROSCOPY OF GRAPHENE-E7 LIQUID-CRYSTAL NANOCOMPOSITE

Todor Vlakhov, Yordan Marinov, Georgi. Hadjichristov, Alexander Petrov

ON THE POSSIBILITY TO ANALYZE AMBIENT NOISERECORDED BYAMOBILEDEVICETHROUGH THE H/V SPECTRAL RATIO TECHNIQUE

Dragomir Gospodinov, Delko Zlatanski, Boyko Ranguelov, Alexander Kandilarov

RHEOLOGICAL PROPERTIES OF BATTER FOR GLUTEN FREE BREAD

G. Zsivanovits, D. Iserliyska, M. Momchilova, M. Marudova

ПОЛУЧАВАНЕ НА ПОЛИЕЛЕКТРОЛИТНИ КОМПЛЕКСИ ОТ ХИТОЗАН И КАЗЕИН

Антоанета Маринова, Теменужка Йовчева, Ася Виранева, Иван Бодуров, Мария Марудова

CHEMILUMINESCENT AND PHOTOMETRIC DETERMINATION OF THE ANTIOXIDANT ACTIVITY OF COCOON EXTRACTS

Y. Evtimova, V. Mihailova, L. A. Atanasova, N. G. Hristova-Avakumova, M. V. Panayotov, V. A. Hadjimitova

ИЗСЛЕДОВАТЕЛСКИ ПРАКТИКУМ

Ивелина Димитрова, Гошо Гоев, Савина Георгиева, Цвета Цанова, Любомира Иванова, Борислав Георгиев

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PARAMETRIC INTERACTION OF OPTICAL PULSES IN NONLINEAR ISOTROPIC MEDIUM

A. Dakova, V. Slavchev, D. Dakova, L. Kovachev

ДЕЙСТВИЕ НА ГАМА-ЛЪЧИТЕ ВЪРХУ ДЕЗОКСИРИБОНУКЛЕИНОВАТА КИСЕЛИНА

Мирела Вачева, Хари Стефанов, Йоана Гвоздейкова, Йорданка Енева

RADIATION PROTECTION

Natasha Ivanova, Bistra Manusheva

СТАБИЛНОСТ НА ЕМУЛСИИ ОТ ТИПА МАСЛО/ ВОДА С КОНЮГИРАНА ЛИНОЛОВА КИСЕЛИНА

И. Милкова-Томова, Д. Бухалова, К. Николова, Й. Алексиева, И. Минчев, Г. Рунтолев

THE EFFECT OF EXTRA VIRGIN OLIVE OIL ON THE HUMAN BODY AND QUALITY CONTROL BY USING OPTICAL METHODS

Carsten Tottmann, Valentin Hedderich, Poli Radusheva, Krastena Nikolova

ИНФРАЧЕРВЕНА ТЕРМОГРАФИЯ ЗА ДИАГНОСТИКА НА ФОКАЛНА ИНФЕКЦИЯ

Рая Грозданова-Узунова, Тодор Узунов, Пепа Узунова

ЕЛЕКТРИЧНИ СВОЙСТВА НА КОМПОЗИТНИ ФИЛМИ ОТ ПОЛИМЛЕЧНА КИСЕЛИНА

Ася Виранева, Иван Бодуров, Теменужка Йовчева

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ТРИ ИДЕИ ЗА ЕФЕКТИВНО ОБУЧЕНИЕ

Гергана Карафезиева

МАГИЯТА НА ТВОРЧЕСТВОТО КАТО ПЪТ НА ЕСТЕСТВЕНО УЧЕНЕ В УЧЕБНИЯ ПРОЦЕС

Гергана Добрева, Жаклин Жекова, Михаела Чонос

ОБУЧЕНИЕ ПО ПРИРОДНИ НАУКИ ЧРЕЗ МИСЛОВНИ КАРТИ

Виолета Стоянова, Павлина Георгиева

ИГРА НА ДОМИНО В ЧАС ПО ФИЗИКА

Росица Кичукова, Ценка Маринова

ПРОБЛЕМИ ПРИ ОБУЧЕНИЕТО ПО ФИЗИКА ВЪВ ВВМУ „Н. Й. ВАПЦАРОВ“

А. Христова, Г. Вангелов, И. Ташев, М. Димидов

ИЗГРАЖДАНЕ НА СИСТЕМА ОТ УЧЕБНИ ИНТЕРНЕТ РЕСУРСИ ПО ФИЗИКА И ОЦЕНКА НА ДИДАКТИЧЕСКАТА ИМ СТОЙНОСТ

Желязка Райкова, Георги Вулджев, Наталия Монева, Нели Комсалова, Айше Наби

ИНОВАЦИИ В БОРБАТА С ТУМОРНИ ОБРАЗУВАНИЯ – ЛЕЧЕНИЕ ЧРЕЗ БРАХИТЕРАПИЯ

Георги Върбанов, Радостин Михайлов, Деница Симеонова, Йорданка Енева

NATURAL RADIONUCLIDES IN DRINKING WATER

Natasha Ivanova, Bistra Manusheva

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АДАПТИРАНЕ НА ОБРАЗОВАНИЕТО ДНЕС ЗА УТРЕШНИЯ ДЕН

И. Панчева, М. Недялкова, П. Петков, Х. Александров, В. Симеонов

STRUCTURAL ELUCIDATION OF UNKNOWNS: A SPECTROSCOPIC INVESTIGATION WITH AN EMPHASIS ON 1D AND 2D 1H NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

Vittorio Caprio, Andrew S. McLachlan, Oliver B. Sutcliffe, David C. Williamson, Ryan E. Mewis

j-j Coupled Atomic Terms for Nonequivalent Electrons of (n-1)f

j-jCOUPLEDATOMICTERMSFORNONEQUIVALENT, ELECTRONS OF (n-f X nd CONFIGURATIONS AND, CORRELATION WITH L-S TERMS

INTEGRATED ENGINEERING EDUCATION: THE ROLE OF ANALYSIS OF STUDENTS’ NEEDS

Veselina Kolarski, Dancho Danalev, Senia Terzieva

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ZAGREB CONNECTION INDICES OF TiO2 NANOTUBES

Sohaib Khalid, Johan Kok, Akbar Ali, Mohsin Bashir

SYNTHESIS OF NEW 3-[(CHROMEN-3-YL)ETHYLIDENEAMINO]-PHENYL]-THIAZOLIDIN-4ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Malesore Pllana, Musaj Pacarizi, Veprim Thaçi, Gjyle Mulliqi-Osmani

2017 година
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GEOECOLOGICAL ANALYSIS OF INDUSTRIAL CITIES: ON THE EXAMPLE OF AKTOBE AGGLOMERATION

Zharas Berdenov, Erbolat Mendibaev, Talgat Salihov, Kazhmurat Akhmedenov, Gulshat Ataeva

TECHNOGENESIS OF GEOECOLOGICAL SYSTEMS OF NORTHEN KAZAKHSTAN: PROGRESS, DEVELOPMENT AND EVOLUTION

Kulchichan Dzhanaleyeva, Gulnur Mazhitova, Altyn Zhanguzhina, Zharas Berdenov, Tursynkul Bazarbayeva, Emin Atasoy

СПИСАНИЕ ПРОСВѢТА

Списание „Просвета“ е орган на Просветния съюз в България. Списанието е излизало всеки месец без юли и август. Годишният том съдържа 1280 стра- ници. Списанието се издава от комитет, а главен редактор от 1935 до 1943 г. е проф. Петър Мутафчиев, историк византолог и специалист по средновеков-

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47-А НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

В последните години тези традиционни за българското учителство конфе- ренции се организират от Българското дружество по химическо образование и история и философия на химията. То е асоцииран член на Съюза на химици- те в България, който пък е член на Европейската асоциация на химическите и

JOURNALS OF INTEREST: A REVIEW (2016)

BULGARIAN JOURNAL OF SCIENCE AND EDUCATION POLICY ISSN 1313-1958 (print) ISSN 1313-9118 (online) http://bjsep.org

INVESTIGATING THE ABILITY OF 8

Marina Stojanovska, Vladimir M. Petruševski

SYNTHESIS OF TiO -M (Cd, Co, Mn)

Candra Purnawan, Sayekti Wahyuningsih, Dwita Nur Aisyah

EFFECT OF DIFFERENT CADMIUM CONCENTRATION ON SOME BIOCHEMICAL PARAMETERS IN ‘ISA BROWN’ HYBRID CHICKEN

Imer Haziri, Adem Rama, Fatgzim Latifi, Dorjana Beqiraj-Kalamishi, Ibrahim Mehmeti, Arben Haziri

PHYTOCHEMICAL AND IN VITRO ANTIOXIDANT STUDIES OF PRIMULA VERIS (L.) GROWING WILD IN KOSOVO

Ibrahim Rudhani, Florentina Raci, Hamide Ibrahimi, Arben Mehmeti, Ariana Kameri, Fatmir Faiku, Majlinda Daci, Sevdije Govori, Arben Haziri

ПЕДАГОГИЧЕСКА ПОЕМА

Преди година-две заедно с директора на Националното издателство „Аз- буки“ д-р Надя Кантарева-Барух посетихме няколко училища в Родопите. В едно от тях ни посрещнаха в голямата учителска стая. По стените ѝ имаше големи портрети на видни педагози, а под тях – художествено написани умни мисли, които те по някакъв повод са казали. На централно място бе портретът на Антон Семьонович Макаренко (1888 – 1939). Попитах учителките кой е Макаренко – те посрещнаха въпроса ми с мълчание. А някога, в г

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„СИМВОЛНИЯТ КАПИТАЛ“ НА БЪЛГАРСКОТО УЧИЛИЩЕ

Николай Цанков, Веска Гювийска

KINETICS OF PHOTO-ELECTRO-ASSISTED DEGRADATION OF REMAZOL RED 5B

Fitria Rahmawati, Tri Martini, Nina Iswati

ALLELOPATHIC AND IN VITRO ANTICANCER ACTIVITY OF STEVIA AND CHIA

Asya Dragoeva, Vanya Koleva, Zheni Stoyanova, Eli Zayova, Selime Ali

NOVEL HETEROARYLAMINO-CHROMEN-2-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Gjyle Mulliqi-Osmani, Veprim Thaçi

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Quantum Connement of Mobile Na+ Ions in Sodium Silicate Glassy

QUANTUM CONFINEMENT OF MOBILE Na + IONS, IN SODIUM SILICATE GLASSY NANOPARTICLES

OPTIMIZATION OF ENGINE OIL FORMULATION USING RESPONSE SURFACE METHODOLOGY AND GENETIC ALGORITHM: A COMPARATIVE STUDY

Behnaz Azmoon, Abolfazl Semnani, Ramin Jaberzadeh Ansari, Hamid Shakoori Langeroodi, Mahboube Shirani, Shima Ghanavati Nasab

EVALUATION OF ANTIBACTERIAL ACTIVITY OF DIFFERENT SOLVENT EXTRACTS OF TEUCRIUM CHAMAEDRYS (L.) GROWING WILD IN KOSOVO

Arben Haziri, Fatmir Faiku, Roze Berisha, Ibrahim Mehmeti, Sevdije Govori, Imer Haziri

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COMPUTER SIMULATORS: APPLICATION FOR GRADUATES’ADAPTATION AT OIL AND GAS REFINERIES

Irena O. Dolganova, Igor M. Dolganov, Kseniya A. Vasyuchka

SYNTHESIS OF NEW [(3-NITRO-2-OXO-2H-CHROMEN4-YLAMINO)-PHENYL]-PHENYL-TRIAZOLIDIN-4-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Hamit Ismaili, Idriz Vehapi, Naser Troni, Gjyle Mulliqi-Osmani, Veprim Thaçi

STABILITY OF RJ-5 FUEL

Lemi Türker, Serhat Variş

A STUDY OF BEGLIKTASH MEGALITHIC COMPLEX

Diana Kjurkchieva, Evgeni Stoykov, Sabin Ivanov, Borislav Borisov, Hristo Hristov, Pencho Kyurkchiev, Dimitar Vladev, Irina Ivanova

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2016 година
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THE EFFECT OF KOH AND KCL ADDITION TO THE DESTILATION OF ETHANOL-WATER MIXTURE

Khoirina Dwi Nugrahaningtyas, Fitria Rahmawati, Avrina Kumalasari

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ОЦЕНЯВАНЕ ЛИЧНОСТТА НА УЧЕНИКА

Министерството на народното просвещение е направило допълне- ния към Правилника за гимназиите (ДВ, бр. 242 от 30 октомври 1941 г.), според които в бъдеще ще се оценяват следните прояви на учениците: (1) трудолюбие; (2) ред, точност и изпълнителност; (3) благовъзпитаност; (4) народностни прояви. Трудолюбието ще се оценява с бележките „образцово“, „добро“, „незадо- волително“. С „образцово“ ще се оценяват учениците, които с любов и по- стоянство извършват всяка възложена им ил

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VOLTAMMERIC SENSOR FOR NITROPHENOLS BASED ON SCREEN-PRINTED ELECTRODE MODIFIED WITH REDUCED GRAPHENE OXIDE

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ИЗСЛЕДВАНЕ НА ПРОФЕСИОНАЛНО-ПЕДАГОГИЧЕСКАТА РЕФЛЕКСИЯ НА УЧИТЕЛЯ ПО БИОЛОГИЯ (ЧАСТ ВТОРА)

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На 8 март 2016 г. в голямата зала на Националния политехнически музей в София фондация „Вигория“ връчи годишните си награди – почетен плакет „Златна детелина“. Тази награда се дава за цялостна професионална и творче- ска изява на личности с особени заслуги към обществото в трите направления на фондация „Вигория“ – образование, екология, култура. Наградата цели да се даде израз на признателност за високи постижения на личности, които на професионално равнище и на доброволни начала са рабо

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ПО ПЪТЯ

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TEACHER’S ACCEPTANCE OF STUDENTS WITH DISABILITY

Daniela Dimitrova-Radojchikj, Natasha Chichevska-Jovanova

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Книжка 4
БЛАГОДАРЯ ВИ!

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SYNTHESIS OF FLUORINATED HYDROXYCINNAMOYL DERIVATIVES OF ANTI-INFLUENZA DRUGS AND THEIR BIOLOGICAL ACTIVITY

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Книжка 2
TEACHING CHEMISTRY AT TECHNICAL UNIVERSITY

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РУМЕН ЛЮБОМИРОВ ДОЙЧЕВ (1938 – 1999)

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145 ГОДИНИ БЪЛГАРСКА АКАДЕМИЯ НА НАУКИТЕ

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V. Romanenko, G. Nikitina Academy of Information Technologies in Education, Russia

ALLELOPATHIC AND CYTOTOXIC ACTIVITY OF ORIGANUM VULGARE SSP. VULGARE GROWING WILD IN BULGARIA

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GENDER ISSUES OF UKRAINIAN HIGHER EDUCATION

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44

Донка Ташева, Пенка Василева

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SCIENTIX – OБЩНОСТ ЗА НАУЧНО ОБРАЗОВАНИЕ В ЕВРОПА

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Книжка 1
ОБРАЗОВАНИЕ ЗА ПРИРОДОНАУЧНА ГРАМОТНОСТ

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DIFFERENTIAL TEACHING IN SCHOOL SCIENCE EDUCATION: CONCEPTUAL PRINCIPLES

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

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Книжка 5

ЗА ХИМИЯТА НА БИРАТА

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Книжка 4
RECASTING THE DERIVATION OF THE CLAPEYRON EQUATION INTO A CONCEPTUALLY SIMPLER FORM

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SIMULATION OF THE FATTY ACID SYNTHASE COMPLEX MECHANISM OF ACTION

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Книжка 2
Книжка 1
COLORFUL EXPERIMENTS FOR STUDENTS: SYNTHESIS OF INDIGO AND DERIVATIVES

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Книжка 6
ADDRESING STUDENTS’ MISCONCEPTIONS CONCERNING CHEMICAL REACTIONS AND SYMBOLIC REPRESENTATIONS

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КОНЦЕПТУАЛНА СХЕМА НА УЧИЛИЩНИЯ КУРС П О ХИМИЯ – МАКР О СКОПСКИ ПОДХОД

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