bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of non-linear discretetime feedback regulators with assignable closed-loop dynamics
Authors: Dubljevic Stevan
Published: July 2008

In the present work the application of a new approach is demonstrated to a discrete-time state feedback regulator synthesis with feedback linearization and pole-placement for non-linear discrete-time systems. Under the simultaneous implementation of a non-linear coordinate transformation and a non-linear state feedback law computed through the solution of a system of non-linear functional equations, both the feedback linearization and pole-placement design objectives were accomplished. The non-linear state feedback regulator synthesis method was applied to a continuous stirred tank reactor (CSTR) under non-isothermal operating conditions that exhibits steady-state multiplicity. The control objective was to regulate the reactor at the middle unstable steady state by manipulating the rate of input heat in the reactor. Simulation studies were performed to evaluate the performance of the proposed non-linear state feedback regulator, as it was shown a non-linear state feedback regulator clearly outperformed a standard linear one, especially in the presence of adverse disturbance under which linear regulation at the unstable steady state was not feasible.
Intellectual property protection of pharmaceutical products and processes
Authors: Ilic-Stojanovic Snezana , Djordjevic Sinisa
Published: July 2008

The role of intellectual property is significantly increasing within new international economic and commercial relationships. Intellectual capital is being increasingly recognised as one of the most important domains belonging to the greatest and the most powerful world companies. Intellectual property protection is a complex category and it comprises legal, technical and economical-financial aspects.
Patents in the pharmaceutical industry
Authors: Jovanovic Slobodanka
Published: July 2008

The pharmaceutical industry is characterized by dynamic development, the existence of big multinational companies and a global market. Such development of the pharmaceutical industry was highly influenced by the introduction of patent protection and compliance with intellectual property regulations. One of the most important international obligations is the TRIPS Agreement.
Development of software for the thermohydraulic analysis of air coolers
Authors: Serbanovic Slobodan , Milosevic Dejan , Djordjevic Emila , Tasic Aleksandar , Djordjevic Bojan
Published: July 2008

Air coolers consume much more energy compared to other heat exchangers due to the large fan power required. This is an additional reason to establish reliable methods for the rational design and thermohydraulic analysis of these devices. The optimal values of the outlet temperature and air flow rate are of particular importance. The paper presents a methodology for the thermohydraulic calculation of air cooler performances, which is incorporated in the "Air Cooler" software module. The module covers two options: cooling and/or condensation of process fluids by ambient air. The calculated results can be given in various ways ie. in the tabular and graphical form.
Influence of the outlet air temperature on the thermohydraulic behaviour of air coolers
Authors: Djordjevic Emila , Serbanovic Slobodan , Milosevic Dejan , Tasic Aleksandar , Djordjevic Bojan
Published: July 2008

The determination of the optimal process conditions for the operation of air coolers demands a detailed analysis of their thermohydraulic behaviour on the one hand, and the estimation of the operating costs, on the other. One of the main parameters of the thermohydraulic behaviour of this type of equipment, is the outlet air temperature. The influence of the outlet air temperature on the performance of air coolers (heat transfer coefficient overall heat transfer coefficient, required surface area for heat transfer air-side pressure drop, fan power consumption and sound pressure level) was investigated in this study. All the computations, using AirCooler software [1], were applied to cooling of the process fluid and the condensation of a multicomponent vapour mixture on two industrial devices of known geometries.
The role and importance of ozone for atmospheric chemistry and methods for measuring its concentration
Authors: Markovic Dragan , Markovic Dragan , Sulic Desanka
Published: July 2008

Depending on where ozone resides, it can protect or harm life on Earth. The thin layer of ozone that surrounds Earth acts as a shield protecting the planet from irradiation by UV light. When it is close to the planet's surface, ozone is a powerful photochemical oxidant that damage, icons frescos, museum exhibits, rubber, plastic and all plant and animal life. Besides the basic properties of some methods for determining the ozone concentration in working and living conditions, this paper presents a detailed description of the electrochemical method. The basic properties of the electrochemical method are used in the construction of mobile equipment for determining the sum of oxidants in the atmosphere. The equipment was used for testing the determination of the ozone concentration in working rooms, where the concentration was at a high level and caused by UV radiation or electrostatic discharge. According to the obtained results, it can be concluded that this equipment for determining the ozone concentration in the atmosphere is very powerful and reproducible in measurements.
The treatment of medical plants: Opportunity and feasability of domestic industry
Authors: Dugalic Sretenka
Published: July 2008

An optimal technology can be determined, among various choices, for manufacturing phytopharmaceutical products by using the model of project profile and risk analysis of investment (comparative analysis of the project value). This technology takes into account different targets: marketing natural and social ones. The production is desirable for producers in Serbia to increase the accumulation of capital. The realization of profit in the production of these products also has ethical reasons because the income is distributed among research, development and social activities. This paper presents some results of research and practice regarding the manufacture of phytotherapy products, which can be useful for managers working on problems of technological restructuring as follows: 1. The feasability study for this production shows that the profit margin is between 10 and 25%. 2. The know-how for the production of phytotherapy products ranges from 12.5 to 25.5% of the total investment in new technology, which can be a great advantage in the development of original (domestic) technology and its export to other countries (example Hemofarm). 3. The development of these products and realized profit improve research for new indication and initiate the production of other equipment (machines for packing, transport etc) Furthermore, some extremely passive regions could be incorporated into such production. The production of phytopharmacy products has a social target supplying the market with cheap medical compounds obtained from plants without any undesired side effects in the treatment.
Ibuprofen: Synthesis, production and properties
Authors: Mijin Dusan , Stankovic Milena , Petrovic Slobodan
Published: July 2008

Since its introduction in 1969, ibuprofen has become one of the most common painkillers in the world. Ibuprofen in an NSAID (non-steroidal anti-inflammatory drug) and like other drugs of its class it possesses analgetic, antipyretic and anti-inflammatory properties. While ibuprofen is a relatively simple molecule, there is still sufficient structural complexity to ensure that a large number of different synthetic approaches are possible. Since the introduction of pharmaceutical products containing ibuprofen, industrial and academic scientists have developed many potential production processes. This paper describes the history, synthesis and production, as well as the properties and stability of ibuprofen.
Influence of the type of exchangeable cation on the electrolytic conductivity of bentonite suspensions
Authors: Dakovic Aleksandra , Raonic Tanja , Matijasevic Srdjan , Tomasevic-Canovic Magdalena , Radosavljevic-Mihajlovic Ana
Published: July 2008

The electrolytic conductivity of bentonite aqueous suspensions was investigated. The starting material (Ca-Mont) was exchanged with sodium ions, using an ion exchange column. The sodium form of bentonite (Na-Mont) was used to obtain organobentonites. The electrolytic conductivity of the starting material, Na-Mont and organobentonites was studied for different suspension concentration. The highest value of the electrolytic conductivity was obtained for Na-Mont, while the organic cation in the bentonite structure decreased the electrolytic conductivity.
Use of gamma Ray computed tomography (CT) and computer aided radioactive particle tracking (CARPT) in multiphase reactors
Authors: Dudukovic Milorad
Published: July 2008

This brief review focuses on the work performed at the Chemical Reaction Engineering Laboratory (CREL) at Washington University, St. Louis, in using Computer Aided Radioactive Particle Tracking (CARPT) and Gamma Ray Computed Tomography (CT), in generating velocity and phase holdup profiles in different multiphase reactors. This data is used for validation of the Euler-Euler interpenetrating fluid model executed in the framework of FLUENT and CFDLIB. Data for holdup and velocity profiles, as well as for mixing parameters, obtained in liquid-solid and gas-solid risers, slurry bubble columns, and stirred tanks, are discussed. It is shown that Euler-Euler simulations are capable of predicting such data well for the cases studied. Extension of CARPT-CT to industrial systems is briefly discussed.
Nanocrystalline functional materials and nanocomposites synthesis through aerosol routes
Authors: Milosevic Olivera , Mancic Lidija , Marinkovic Zorica , Ohara Saloshi , Fukui Takehisa , Varez Alejandro , Torralba Jose
Published: July 2008

This paper represents the results of the design of functional nanocrystalline powders and nanocomposites using chemical reactions in aerosols. The process involves ultrasonic aerosol formation (mist generators with the resonant frequencies of 800 kHz, 1.7 and 2.5 MHz) from precursor salt solutions and control over the aerosol decomposition in a high-temperature tubular flow reactor. During decomposition, the aerosol droplets undergo evaporation/drying, precipitation and thermolysis in a single-step process. Consequently, spherical, solid, agglomerate-free submicronic particles are obtained. The particle morphology, revealed as a composite structure consisting of primary crystallites smaller than 20 nm was analysed by several methods (XRD, DSC/DTA, SEM, TEM) and discussed in terms of precursor chemistry and process parameters. Following the initial attempts, a more detailed aspect of nanocrystalline particle synthesis was demonstrated for the case of nanocomposites based on ZnO-MeO (MeO=Bi Cr+), suitable for electronic applications, as well as an yttrium-aluminum base complex system, suitable for phosphorus applications. The results imply that parts of the material structure responsible for different functional behaviour appear through in situ aerosol synthesis by processes of intraparticle agglomeration, reaction and sintering in the last synthesis stage.
The model of back-flow mixed tanks-in-series used for representing the liquid flow in a reciprocating plate column
Authors: Nikolic Ljubisa , Stojanovic Sreten , Veljkovic Vlada , Skala Dejan
Published: July 2008

The influence of different working parameters (vibration intensity superficial gas and liquid rate and content of the solid phase) on liquid flow in a multiphase (gas-liquid: RPC-II and gas-liquid-solid: RPC-III) reciprocating plate column was analyzed using step-response methods and sorbic acid as a tracer. The liquid flow was determined using a model of N-tanks in series followed by back mixing of the liquid phase between the tanks. The parameters of this model N, a and x were calculated by applying several methods: calculation of the moments of the residence time distribution function for a constant number of tanks in series (N=const) analysis of a set of linear equations for N *const and determination of the minimum of defined goal function using the optimization technique leastsq.m of MATLAB software.
Studies on oxygen mass transfer in stirred bioreactors 2: Suspensions of bacteria, yeasts and fungis
Authors: Galaction Anca-Irina , Oniscu Corneliu , Cascaval Dan
Published: July 2008

The aim of these experiments is to study the oxygen mass transfer rate by means of the mass transfer coefficient, for a stirred bioreactor and different fermentation broths, using a large domain of operating variables. For quantifying the effects of the considered factors (concentration and morphology of the biomass, specific power input, superficial air velocity surface aeration) on k\a, the experiments were carried out for non-respirating biomass suspensions of Propionibacterium shermanii Saccharomyces cerevisiae and Penicillium chrysogenum, mycelial aggregates (pellets) and free mycelia morphological structures.
Solid-liquid systems for the hydrolysis of glycoalkaloids from potato (Solanum tuberosum L) tuber sprouts and solanidine isolation
Authors: Nikolic Nada , Stankovic Mihajlo , Cakic Milorad
Published: July 2008

Solanidine (C17H43O/V) is a steroidal aglycone of glycoalkaloids and an important precursor for the synthesis of hormones and some pharmacologically active compounds. Glycoalkaloids are hydrolysed by mineral acid yielding solanidine and a carbohydrate moiety. In this paper the kinetics of hydrolysis of glycoalkaloids from potato (Solanum tuberosum L) tuber sprouts by using solid-liquid systems were studied as well as solanidine isolation from the liquid phase of the system. The dried and milled tuber sprouts of potato were used as the solid phase and solutions of hydrochloric acid of different concentration in 96 % vol. ethanol, mixed with chloroform in a volume ratio of 2:3, 1:1, 3:2 and 4:1, were used as the liquid phase. The aim of the paper was to choose the optimal concentration of hydrochloric acid in ethanol, the volume ratio of hydrochloric acid in ethanol to chloroform in the liquid phase and the time for solanidine hydrolytic extraction, as well as to isolate solanidine from the liquid phase.
Absorption in a three-phase fluidized bed I: Hydrodynamic investigations
Authors: Pejanovic Srdjan
Published: July 2008

The hydrodynamic properties of a three phase fluidized bed with low density inert spherical packing, fluidized by the interaction of a gas flowing upwards and a liquid flowing downwards through the column, were investigated. It was found that the pressure drop, liquid hold up and dynamic bed height increase with both increasing liquid and gas flow rate. While the dynamic bed height and minimum fluidization velocity remain unchanged, both the pressure drop and liquid hold up increase with increasing density of the packing. Therefore, an increase in packing density causes more intensive mass transfer between the fluid phases than packed columns. It was shown that increase of the liquid flow rate causes an increase of both the effective liquid and gas velocity through the fluidized bed, which may also improve mass transfer.
Absorption in a three-phase fluidized bed II: Mass transfer investigations
Authors: Pejanovic Srdjan , Garic-Grulovic Radmila , Bozalo Predrag
Published: July 2008

The absorption of carbon dioxide in aqueous diethanolamine solutions was carried out in a three-phase fluidized bed with inert spherical packing. The rate of absorption was calculated on the basis of measuring the concentration change in the liquid phase on-line by a conductivity probe. It was shown that the Danckwerts plot method might be successfully used to simultaneously determine the effective interfacial area and both the gas and liquid-side mass transfer coefficients. While the gas-side mass transfer coefficient is independent of the liquid flow rate, the effective interfacial area and liquid-side mass transfer coefficient increase with increasing liquid flow rate.
Investigation of the washing conditions of domestic types of wool
Authors: Ristic Mihailo , Janjic Svjetlana , Iliskovic Nadezda , Gojic Dusko
Published: July 2008

The wool fibers that are obtained in the Republic of Serbs have not been systematically analyzed. Also, they are only used in domestic crafts production, not for industrial means. This study is the beginning of a project with the aim of determining how to replace a quantity of imported wool by domestic wool in the process of industrial manufacturing.The washing of two types of domestic wool was investigated, namely pramen-ka and polumerino. The parameters used to wash this wool were varied, such as materials for washing (from clean water to surfactants and additives), as well as the temperature and length of the washing process.The effects of washing the wool were tested with respect to the content of clean wool, the content of organic materials soluble in ethanol, the content of herbal components insoluble in sodium-hydroxide solutions and mineral substances represented as ash quantities. The optimal conditions for washing wool were defined, as well as recommendations for the more economic usage of materials used in washing.
The determination of individual mass transfer coefficients in liquid-liquid extraction
Authors: Radu Tudose , Lisa Gabriela
Published: July 2008

An improved Lewis cell has been used as an efficient method to determine the mass transfer coefficient for any ternary multi-component system. In this paper the individual mass transfer coefficients were determined for three ternary systems: water-acetone-carbon tetrachloride water-acetone-chloroform and water-acetone-toluene, using the improved Lewis cell. Criteria! equations were developed to calculate the mass transfer coefficients when one or both (organic and aqueous) phases were agitated and when solute transfer occurs in both directions.
Aromatization of light naphtha fractions on zeolites 1: Kinetic model
Authors: Rovenskaja Svetlana , Ostrovski Nikolaj
Published: July 2008

On the basis of analyzing kinetic experimental data performed in laboratory integral reactors a lumping kinetic model of the "Zeoforming" process was developed. A reaction scheme of the lumped components was proposed, that was adapted to the technological requirements. The reaction rate constants and activation energies were estimated, that are valid for certain feed compositions. The model is intended for further modeling and optimization of the process.
Iron complexes of pharmaceutical interest: Antianemics
Authors: Cakic Milorad , Nikolic Goran
Published: July 2008

Preparations based on different compounds of bi- and trivalent iron are curently used for the prevention and therapy of sideropenic anemia in human and veterinary medicine. The application of preparations based on dextran started about 1950. Up to now, synthesis and production of preparations were performed with the purpose of improving pharmacological performance by using dextran oligosaccharides with different weight - average molar masses and their oxidized and hydrogenated derivatives. Synthesis of polynuclear iron(lll) complexs with other oligosaccharides (inulin and pullulan) and their derivatives was developed, with potential or valid pharmacological activity for sideropenic anemia treatment.A Review of iron(lll) complexes with different oligosaccharides, their physico-chemical characterization pharmaco-biological performance, global structure, further research and possible applications of then complexes, are presented in this paper.
Modern technologies and food safety
Authors: Grujic Radoslav
Published: July 2008

To resolve the problem of lack of food in the World within primary food production, processing and procedures of preserving, new methods have been implemented (implementation of materials for protection, medications utilization of new areas for production purposes, use of GM microorganisms plants, even animals, utilization of food additives, introduction of new procedures of preservation, etc) However, these procedures do not always move in the direction of ensuring food safety. Implementation of mentioned procedures creates resistance by consumers. The opinion and the attitude about this issue are very important all over the World. According to recent research performed in last five years, most of the population of developed and semi-developed countries considers food safety a priority, as second place the presence of ingredients that can be harmful for human health and as third the content of nutrients required for normal functioning of the body. The WHO, CAC, WTO and other international institutions support these attitudes of consumers. There is more and more obvious pressure on food producers to preserve the environment, which has resulted in the introduction of production procedures known as "cleaning production".Regardless of which procedure is involved, it is necessary to implement the efficient quality control system and food safety. It is mandatory to request the compulsory implementation of different systems that are defined through the GMR GHR HACCR ISO 9000. In food production, these systems are complementary and only with full implementation of all of them in practice will if be possible to ensure the continuous production of quality and safe products. Food production must be seen as an undisturbed chain: primary production, transport, processing, storage, distribution and consumption. With strict implementation of the mentioned standards in all parts of the chain, the risk of injuries and poisoning of consumers will be decreased to the minimum, and the whole chain will be under control.
Kombucha - functional beverage: Composition, characteristics and process of biotransformation
Authors: Markov Sinisa , Jerinic Veronika , Cvetkovic Dragoljub , Loncar Eva , Malbasa Radomir
Published: July 2008

Kombucha is a refreshing beverage obtained by the proces of biotransformation of sugared tea with a tea fungus. Kombucha is also frequently called "tea fungus" in the literature, although there is actually no fungus involved in the fermentation. The tea fungus is a symbiotic association of native yeasts and Acetobacteriaceae species fermenting sugared (5-10%) black tea (0.2-0.5%) into a kombucha beverage. After about 7-10 days incubation at room temperature, kombucha is ready. Growth patterns of tea fungus microorganisms during the biotransformation process of kombucha are not well documented. Tea fungus produces many substances, which with the supply of tea nutrients, give the drink its unusual flavour and healthy properties.
Modern cosmetic products for skin care: Formulations and quality requirements
Authors: Vuleta Gordana , Milic-Askrabic Jela , Cekic Nebojsa
Published: July 2008

The efficiency of modern cosmetic products mostly involves multifunctionality. The denoted requirements impose on producers of cosmetic raw materials and preparations the continuous improvement of formulations of existing emulsion supports for cosmetically active substancs, the use of new raw materials and technologies for manufacturing preparations, as well as the development of completely new supports for active components and a large number of various sources and concepts for obtaining cosmetically active substances. Special requirements for the quality of cosmetic raw materials and products are analyzed, as well as the corresponding legislation.
Alkaloids in the pharmaceutical industry: Structure, isolation and application
Authors: Nikolic Milan , Djordjevic Sinisa
Published: July 2008

By the end of the 18th and the beginning of the 19th century a new era began in medicine, pharmaceutics and chemistry that was strongly connected with alkaloids and alkaloid drugs. Even before that it was known that certain drugs administered in limited doses were medicines, and toxic if taken in larger doses (opium, coke leaves, belladonna roots, monkshood tubers crocus or hemlock seeds). However, the identification, isolation and structural characterization of the active ingredients of the alkaloid drugs was only possible in the mid 20th century by the use of modern extraction equipment and instrumental methods (NMR, X-ray diffraction and others).In spite of continuing use over a long time, there is still great interest in investigating new drugs, potential raw materials for the pharmaceutical industry, as well as the more detailed investigation and definition of bio-active components and the indication of their activity range, and the partial synthesis of new alkaloid molecules based on natural alkaloids. The scope of these investigations, especially in the field of semi-synthesis is to make better use of the bio-active ingredients of alkaloid drugs, i.e. to improve the pharmacological effect (stronger and prolonged effect of the medicine, decreased toxicity and side effects), or to extend or change the applications. A combined classification of alkaloids was used, based on the chemical structure and origin, i.e. the source of their isolation to study alkaloid structure. For practical reasons, the following classification of alkaloids was used: ergot alkaloids, poppy alkaloids, tropanic alkaloids purine derivative alkaloids, carbon-cyclic alkaloids, and other alkaloids. The second part of this report presents a table of general procedures for alkaloid isolation from plant drugs (extraction by water non-miscible solvents, extraction by water-miscible solvents and extraction by diluted acid solutions). Also, methods for obtaining chelidonine and glaucine as hydrochloride bases and salts were presented in more details. Data from leading world pharmacopoeias (Ph. Eur. Ill/s 2000, DAB 1996, USP 23, JP XIII, BP 1993, Ph. Jug. IV) were used in the study of application of the pure alkaloids in pharmaceutical forms with predetermined doses. A comparative study of these data shows that a great number of preparations are produced worldwide based on alkaloids and alkaloids with modified structure. These medicines have found use in modern therapeutic practice in many countries. Most products are produced on the basis of caffeine, theophylline, ephedrine, atropine, scopolamine, reserpine and pilocarpine.
Bioprotective agents in safety control
Authors: Dimitrijevic-Brankovic Suzana
Published: July 2008

Food poisoning is the one of the main health hazards even today. More than 200 known diseases are transmitted through food. The causes of foodborne illness include viruses, bacteria, parasites, toxins, metals, and prions and the symptoms of foodborne illness range from mild gastroenteritis to life-threatening neurological, hepatic and renal syndromes.The prevention of food poisonings represents very serious task for food manufacturers. Beside food control according to the concept "from the farm to the table" there is increased need for the development of new technology for longer shelf lifes of food. Food fermented by lactic acid bacteria (LAB) and traditionally considered to be safe. There are many substances produced by LAB that affect the shelf life of fermented food, by active suppression of poisoning microorganisms growth. Because of that, the LAB is recently considered as bioprotective agents that have important role in food safety.
Use of modern methods of fibre surface modification to obtain the multifunctional properties of textile materials
Authors: Jocic Dragan , Jovancic Petar , Radetic Maja , Topalovic Tatjana , Petrovic Zoran
Published: July 2008

The modern textile fibre treatments aim to obtain the required level of beneficial effect while attempting to confine the modification to the fibre surface. Recently, much attention has been focused on different physical methods of fibre surface modification, cold plasma treatment being considered as very useful. Moreover, there are efficient chemical methods available, such as peroxide, biopolymer and enzyme treatment. Some interesting combinations of these physical and chemical surface modification methods as means to modify fibre surface topography and thus controlling the surface-related properties of the fibre are presented in this paper. The properties obtained are discussed on the basis of the physico-chemical changes in the surface layer of the fibre, being assessed by wettability and contact angle measurements, as well as by FTIR-ATR and XPS analysis. The SEM and AFM technique are used to assess the changes in the fibre surface topography and to correlate these changes to the effectiveness, uniformity and severity of the textile fibre surface modification treatments.
Biodegradable polyesters based on succinic acid
Authors: Nikolic Marija , Poleti Dejan , Djonlagic Jasna
Published: July 2008

Two series of aliphatic polyesters based on succinic acid were synthesized by copolymerization with adipic acid for the first series of saturated polyesters, and with fumaric acid for the second series. Polyesters were prepared starting from the corresponding dimethyl esters and 1,4-butanediol by melt transesterification in the presence of a highly effective catalyst tetra-n-butyl-titanate, Ti(0Bu)4. The molecular structure and composition of the copolyesters was determined by 1H NMR spectroscopy. The effect of copolymer composition on the physical and thermal properties of these random polyesters were investigated using differential scanning calorimetry. The degree of crystallinity was determined by DSC and wide angle X-ray. The degrees of crystallinity of the saturated and unsaturated copolyesters were generally reduced with respect to poly(butylene succinate), PBS. The melting temperatures of the saturated polyesters were lower, while the melting temperatures of the unsaturated copolyesters were higher than the melting temperature of PBS. The biodegradability of the polyesters was investigated by enzymatic degradation tests. The enzymatic degradation tests were performed in a buffer solution with Candida cylindracea lipase and for the unsaturated polyesters with Rhizopus arrhizus lipase. The extent of biodegradation was quantified as the weight loss of polyester films. Also the surface of the polyester films after degradation was observed using optical microscopy. It could be concluded that the biodegradability depended strongly on the degree of crystallinity, but also on the flexibility of the chain backbone. The highest biodegradation was observed for copolyesters containing 50 mol.% of adipic acid units, and in the series of unsaturated polyesters for copolyesters containing 5 and 10 mol.% of fumarate units. Although the degree of crystallinity of the unsaturated polyesters decreased slightly with increasing unsaturation, the biodegradation was not enhanced suggesting that not only the chemical structure and molecular stiffness but also the morphology of the spherulites influenced the biodegradation properties.
Semi-interpenetrating polymer networks based on polyacrylamide and poly[itaconic acid]
Authors: Kalagasidis-Krusic Melina , Nikolic Biljana , Filipovic Jovanka
Published: July 2008

The effect of pH and temperature on the equilibrium swelling properties of PIA/PAAm semi-IPNs were investigated.Semi-IPNs based on polyacrylamide (PAAm) and poly(itaconic acid) (PIA) were prepared by two different techniques, by polymerizing itaconic acid in the presence of polyacrylamide gel (Semi-IPNs-l) and by making the polyacrylamide gel in the presence of previously synthesized poly(itaconic acid) (Semi-IPNs-ll), with different PIA/PAAm mass ratios. The equilibrium swelling degree of an ionic network depends very much on the concentration of ionisable groups. The addition of a small amount of itaconic acid dramatically changes the swelling behavior of PAAm. Increase of the ionic monomer (IA) produces swelling degrees that increase to a high extent when the pH of the buffer solution is higher than the nominal pKa values of the acid groups. Gels with higher IA content swell less than PAAm gels in low pH buffers. At low pH, when complexation due to hydrogen bonding occurs between the carboxylic groups and amide groups of acrylamide, the polymer network collapses and the swelling ratio is low. The presence of hydrogen bonds in the complexes causes additional constraints in the network, acting as a physical crosslinking and makes the network less hydrophilic, because the carboxylic groups on the PIA are occupied in the complexes. As opposed to this, the equilibrium swelling degrees change very little with pH of the solution in nonionic PAAm gel.Hydrogels exhibit continuous changes in water content as a function of temperature. The swelling degree increases with increasing temperature due to gel expansion upon warming.
Rheological properties of concentrated solutions of carboxymethyl starch
Authors: Stojanovic Zeljko , Jeremic Katarina , Jovanovic Slobodan
Published: July 2008

Carboxymethyl starch was synthesized by the esterification of starch with monochloroacetic acid in ethanol as a reaction medium. Three samples of carboxymethyl starch having different degrees of substitution were prepared. The influence of temperature on the viscosity of concentrated carboxymethyl starch solutions, as well as the dynamic-mechanical properties of the concentrated solutions were investigated. The activation energy of viscous flow was determined and it was found that it decreased with increasing degree of substitution. The results of the dynamic-mechanical measurements showed that solutions of starch and carboxymethyl starches with higher degrees of substitution behave as gels. Values of the storage modulus in the rubbery plateau were used to calculate the molar masses between two points of physical crosslinking, the density of crosslinking and the distance between two points of crosslinking.
Radical polymerization of monoethyl itaconate
Authors: Katsikas Lynne , Nisevic Natasa , Ignjatovic Milka , Adamovic Vladimir , Djakov Tatjana , Popovic Ivanka
Published: July 2008

The radical polymerization of monoethyl itaconate (MEI) was investigated in bulk and in solution at 60?C using a,a'-azobisisobutyronitrile as initiator. It was established that the obtained polymer poly(monoethyl itaconate) was insoluble in its monomer, implying that the bulk polymerization of MEI was a precipitation polymerization. The polymerization kinetics of MEI were discussed and compared to the polymerization kinetics of structurally similar alkyl itaconates. The homogeneous radical polymerization of MEI in tetrahydrofuran was not possible in the whole range of monomer/solvent concentration ratios, while the polymerization of MEI in methanol was homogeneous. The chain transfer constants to THF and methanol at 60?C were determined.
Determination of the cross-linking degree of unmodified epoxy resin by cycloaliphatic polyamine and polyamidamin hardeners by ftir spectroscopy
Authors: Zlatkovic Sasa , Nikolic Goran , Stamenkovic Jakov
Published: July 2008

Unmodified epoxy resin GY250 was crosslinked by the cycloaliphatic polyamino hardener HY847 and polyamidamine hardener HY848 in the different mass ratios. The degree of crosslinking of the epoxy resin and the quantity of unreacted epoxy groups were determined by a spectroscopic FTIR method. The optimal time of complete crosslinking, as a criterion of the degree, was determined by measuring the film hardness indirectly (JUS H.C8.055). The optimal stoichiometric ratio of 100:18:32 (GY250:HY847:HY848) was defined by correlating parameters which directly depend on the degree of crosslinking and the period of application of the epoxy resins, as a prerequisite for forming 2-component epoxy systems which are comparatively more elastic adhesive and waterproof.
Phase topology of a NR/BR elastomer blend with active filler
Authors: Plavsic Milenko , Pajic-Lijakovic Ivana , Cubric Branislav , Popovic Radivoj , Bugarski Branko , Popovic Ruzica , Lazic Nada
Published: July 2008

The relations between the structure and mechanical properties of a polymer blend of natural (NR) and polybutadiene (BR) rubber (i.e. a NR/BR blend with the weight ratio of the components 70/30) filled with active carbon black were analysed. The properties of the individual phases in the blend were resolved by modeling the stress-strain relationship according to the Bauer procedure for high extensions. The obtained results indicated that BR is the dispersed phase, having a higher modulus, which was also confirmed by the much better fit of the experimental data to the series type of phase coupling according to the Takanayagy theory.
Multienzymatic system encapsulation: Application to the lactoperoxidase system
Authors: Jacquot Muriel , Poncelet Denis
Published: July 2008

The use of enzyme often implicates a stabilization to limit loss of activity and a suitable dry formulation to simplify handling. Freeze drying and spray drying are two classic methods but when complex systems are studied, it becomes difficult to achieve a correct formulation. In this work, the realization of a dry microbead containing a multienzymatic system (2 enzymes, 2 substrates) is presented. The lactoperoxidase system associated with an enzymatic hydrogen peroxide generator was chosen as the model. The microbead, made by spray drying and spray coating, was characterized in terms of size, shape, chemical structure, flow ability, encapsulation efficiency and antimicrobial activity. Different compositions of the coat were tested, as well as their influence on the bead properties.
Encapsulated multicellular tumor spheroids as a novel in vitro model to study small size tumors
Authors: Markvicheva Elena , Bezdetnaya Lina , Bartkowiak Artur , Marc Annie , Gorgen Jean-Louis , Guillemin Francois , Poncelet Denis
Published: July 2008

Presently multicellular tumor spheroids (MTS) are being widely used in various aspects of tumor biology, including studies in biology and photodynamic therapy. The cellular organization of spheroids allows the recreation of in vivo small tumors much better than all common two-dimensional in vitro models. The cell encapsulation method could be proposed as a novel technique to quickly and easily prepare a large number of spheroids with narrow size distribution within a desirable diameter range. Moreover, the proposed technique for spheroid generation using encapsulated growing tumor cells could provide entirely new avenues to develop a novel spheroid co-culture model (for instance, the in vitro co-cultvation of tumor cells and monocytes, or epithelial cells, or fibroblasts etc). The current research was aimed at developing a simple and reliable method to encapsulate tumor cells and to cultivate them in vitro. In order to generate spheroids, MCF-7 cells were encapsulated and cultivated in 200 ml T-flasks in a 5% CO2 atmosphere at 37?C for 4-5 weeks. The cell proliferation was easily observed using a light microscope. The cells grew in aggregates increasing in size with time. The cell growth resulted in the formation of large cell clusters (spheroids) which filled the whole microcapsule volume in 4-5 weeks.
Bioreporter pseudomonas fluorescens HK44 immobilized in a silica matrix
Authors: Trogl J. , Ripp S. , Kuncova G. , Sayler G.S. , Demnerova K.
Published: July 2008

The bioluminescent bioreporter Pseudomonas fluorescens HK44, the whole cell bacterial biosensor that responds to naphthalene and its metabolites via the production of visible light, was immobilized into a silica matrix by the sol-gel technique. The bioluminescence intensities were measured in the maximum of the bioluminescence band at X = 500 nm. The immobilized cells (>105 cells per g silica matrix) produced light after induction by salicylate (cone. > 10 g/l), naphthalene and aminobenzoic acid. The bioluminescence intensities induced by 2,3-dihydroxynaphthalene 3-hydroxybenzoic acid and 4-hydroxybenzoic acid were comparable to a negative control. The cells in the silica layers on glass slides produced light in response to the presence of an inductor at least 8 months after immobilization, and >50 induction cycles. The results showed that these test slides could be used as assays for the multiple determination of water pollution.
Characterization of agarose as immobilization matrix model for a microbial biosensor
Authors: Pernetti Mimma , Poncelet Denis , Thouand Gerald , Annesini Maria , Merli Carlo
Published: July 2008

Microbial biosensors are promising tools for the detection of specific substances in different fields, such as environmental, biomedical, food or agricultural. They allow rapid measurements, no need for complex sample preparation or specialized personnel and easy handling. In order to enhance the managing, miniaturization and stability of the biosensor and to prevent cell leaching, bacteria immobilization is desirable. A systematic characterization procedure to choose a suitable immobilization method and matrix, was proposed in this study. Physical properties, storage stability mass transport phenomena and biocompatibility were evaluated, employing agarose as the model matrix. Preliminary essays with bioluminescent bacteria detecting Tributyltin were also carried out.
Immobilization of fish chromatophores for use as a micro-biosensor for biological toxins
Authors: Mojovic Ljiljana , Jovanovic Goran
Published: July 2008

Chromatophores isolated from the Siamese fighting fish, Betta splendens represent a class of living cells that provide a vivid color response to microbial pathogens and environmental toxins. The selection of the most appropriate microcarrier and the development of the optimal technique for the chromatophore immobilization in order to enable directed transport of the sensor cells throughout microchannels of the biosensor, as well to preserve the cell survival and its functionality was studied. Microcarriers derived from glass, polystyrene and gelatin (collagen) were tested as substrates for chromatophore attachement. Gelatin microcarriers were found to be the most suitable, due to high attachment efficiency (95% of attached cells), preservation of the cell viability and enhanced cell sensitivity. The optimum conditions for fish cell immobilization on collagen microcarriers were determined based on the cell-to-microcarrier bead ratio and the pH of the solution. The rate of cell attachment to the gelatin microcarrier followed first-order kinetics. Pretreatment of the gelatin beads with fibronectin, known as a cell attachment-promoting agent, resulted in a 10% higher attachment rate constant (k).
Whey protein-derived biomaterials and their use as bioencapsulation and delivery systems
Authors: Subirade Muriel , Remondetto Gabriel , Beaulieu Lucie
Published: July 2008

The emergence of bioactive food compounds (nutraceutical compounds) with health benefits provides an excellent opportunity for improving public health. The incorporation of bioactive compounds into food systems is therefore of great interest to researchers in their efforts to develop innovative functional foods that may have physiological benefits or reduce the risk of disease beyond basic nutritional functions. However, the effectiveness of these products in preventing diseases relies on preserving the bioavailability of their active ingredients. This represents undoubtedly a great challenge since these molecules are generally sensitive to environmental conditions encountered in food processes (i.e., temperature oxygen, and light) or in the gastrointestinal tract (i.e., pH, enzymes presence of other nutrients), which limit their activity and potential health benefits. However, bio- and microencapsulation can be used to overcome these limitations. Whey proteins, also known as the serum proteins of milk, are widely used in food products, because of their high nutritional value and their ability to form gels, emulsions, or foams. The aim of this article is to provide information on the different types of materials obtained from whey proteins and to examine their use as bioencapsulation and delivery systems.
Approaches to new derivatives of cellulose as designed pharmaceutical excipients
Authors: Schwarz Brigitte , Loppert Renate , Praznik Werner , Unger Frank , Kahlig Hanspeter , Viernstein Helmut
Published: July 2008

Recently, our group initiated a synthetic program directed at new derivatives of cellulose intended as novel pharmaceutical excipients. With several notable exceptions, the attempted regioselective introduction of chemical functionality into natural cellulose by direct chemical modification will result in heterogeneous products that are difficult to characterize and the preparation of which is insufficiently reproduceable. Approaches to the chemical polymerization of appropriate glucose monomers are available, leading to a degree of polymerization in the order of 100. However, the nature of these processes does not readily lend itself to the preparation of products comprising regularly arranged protecting groups in defined positions. We have chosen a mixed organic chemical-enzyme catalyzed approach based on a procedure of Kobayashi, Shoda, Donnelly and Church. Fluoride derivatives of cellobiose may be polymerized, under catalysis by cellobiose hydrolase, to form cellulose oligosaccharides of different chain lengths. We describe the chemical syntheses of cellobiose fluoride derivatives comprising protecting groups in defined positions of the reducing or nonreducing glucose moieties of cellobiose. Such derivatives may be polymerized to afford cellulose derivatives with protecting groups on alternate glucose units. The processing of these protected cellulose derivatives to afford novel biomimetic polymers will be described.
Mass transfer ranking of polylysine, poly-ornithine and poly-methylene-co-guanidine microcapsule membranes using a single low molecular mass marker
Authors: Rosinski Stefan , Lewinska Dorota , Orive Gorka , Pedraz Jose
Published: July 2008

On the long way to clinical transplantable hybrid systems, comprising of cells, acting as immuno-protected bioreactors microencapsulated in a polymeric matrix and delivering desired factors (proteins, hormones, enzymes etc) to the patient's body, an important step is the optimization of the microcapsule. This topic includes the selection of a proper coating membrane which could fulfil, first of all, the mass transfer as well as biocompatibility, stability and durability requirements. Three different membranes from polymerised aminoacids, formed around exactly identical alginate gel cores, were considered, concerning their mass transport properties, as potential candidates in this task. The results of the evaluation of the mass ingress and mass transfer coefficient h for the selected low molecular mass marker, vitamin B12, in poly-L-lysine (HPLL) poly-L-ornithine (HPLO) and poly-methylene-co-guanidine hydrochloride (HPMCG) membrane alginate microcapsules demonstrate the advantage of using the mass transfer approach to a preliminary screening of various microcapsule formulations. Applying a single marker and evaluating mass transfer coefficients can help to quickly rank the investigated membranes and microcapsules according to their permeability. It has been demonstrated that HPLL, HPLO and HPMCG microcapsules differ from each other by a factor of two concerning the rate of low molecular mass marker transport. Interesting differences in mass transfer through the membrane in both directions in-out was also found, which could possibly be related to the membrane asymmetry.