bluuebunny/crossref_metadata_2025 huggingface dataset:
Akinetic model for the consumption of stabilizer in single base gun propellants
Authors: Jelisavac Ljiljana , Filipovic Milos
Published: August 2005

A suitable kinetic model for the consumption of stabilizer (diphenylamine) in single base gun propellants was investigated and successfully verified. The model assumes that a reaction of shifting order can be applied for the consumption of diphenylamine in single base gun propellants. It was found that the experimental data were well evaluated by a first-order reaction at high concentrations of diphenylamine in the propellant, but by a zero-order reaction at low concentrations during the final phase of the propellant life time. The mechanism of diphenylamine depletion was discussed with relation to the model and the ageing behavior of the propellants. The kinetic parameters of this model, which permit the calculation of the time up to complete consumption of the diphenylamine, were determined. The results were compared with the kinetic data obtained by a widely accepted model, which combines formally reactions of first and zero order, designated as an "exponential and linear" model. All comparisons gave satisfactory agreement.
Synthesis and characterization of tris[butyl-(1-methyl-3phenyl-propyl)-dithiocarbamato]cobalt(III) seskvitoluen
Authors: Kaludjerovic Goran , Djinovic Vesna , Trifunovic Srecko , Hodzic Ismet , Sabo Tibor
Published: August 2005

Anew bidentate ligand butyl-(1-methyl-3-phenyl-propyl)-dithiocarbamate (bm?pdtc) was prepared, as the sodium salt. In the reaction of hexaaminecobalt(III) chloride with Nabm?pdtc, the corresponding tris[butyl-(1-methyl-3-phenyl-propyl)-dithiocarbamato]cobalt(III) [Co(bm?pdtc)3]?complex was prepared. The complex was characterized by elemental analysis, infrared, electronic absorption, 1H and 13C-NMR spectroscopy.
Glass-ceramic enamels derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system
Authors: Gavrilovski Dragica , Blagojevic Nikola , Gavrilovski Milorad , Grujic Snezana
Published: August 2005

The results of research on the conditions for obtaining model glass-ceramic enamels, derived from the basic Li2O-Na2O-Al2O3-TiO2-SiO2 system, by varying the initial composition and thermal treatment conditions, are presented in this paper. Segregation of the crystal phases in the glassy-matrix was carried out during subsequent thermal treatment. The formation of different crystal phases was evidenced through the results of differential-thermal analysis and X-ray powder diffraction analysis.
Modeling glass-ceramic enamel properties
Authors: Gavrilovski Dragica , Blagojevic Nikola , Gavrilovski Milorad
Published: August 2005

The results of an investigation of the chemical and thermal characteristics of glass-ceramic enamels, derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system obtained by employing the methods of mathematical experiment planning, are presented in this paper. Adequate mathematical models, showing the dependence of the chemical and thermal stability on the chemical composition of enamel systems, after different thermal treatment procedures, were obtained. Based on the testing carried out, it was concluded that in the obtained glass-ceramic enamels the chemical resistance is decreased, but at the same time, the thermal stability is increased, relative to reference coatings.
Investigations of the lysophospholipid composition of human neutrophils under different stimulation conditions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry
Authors: Petkovic Marijana , Schiller Jurgen , Müller Matthias , Arnold Klaus , Arnhold Jurgen
Published: August 2005

Matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS) is usually used for the analyses of proteins carbohydrates and oligonucleotides. In spite of the number of advantages that MALDI-TOF MS exhibits for lipid analysis, this method has not often been applied in this field. In this paper we have extended our previous studies on the suitability of MALDI-TOF MS for the investigation of changes in the content of lipid-derived second messengers in organic extracts of human neutrophils. Qualitative differences in the lysophospholipid composition in organic extracts of the human neutrophils under different stimulation conditions could be easily observed by MALDI-TOF MS. Although there are still some methodological problems to be solved before this method can be routinely applied for the quantification of different lipid classes in complex biological mixtures (such as organic extracts of human neutrophils) it is shown here that MALDI-TOF MS possesses the capability to be used as a simple screening method for the investigation of the content of lipid-derived second messengers and of signalling pathways in cells.
Protolytic equlibria of bromazepam
Authors: Pfendt Lidija , Popovic Gordana , Damjanovic Tatjana , Sladic Dusan
Published: August 2005

The protolytic equilibria of bromazepam, an ampholyte sparingly soluble in water, in homogeneous and heterogeneous systems were studied in the pH range 0?14 at 25?C and at ionic strength of 0.1 mol/dm3 (NaCl). On the basis of 13C-NMR spectra, the protonation site was predicted ? in acidic media the pyridine nitrogen of bormazepam is protonated. The acidity constants of bromazepam were determined spectrophotometrically (pKa1 2.83 and pKa2 11.60) and potentiometrically (pKa1 2.99). In the heterogeneous system the following equilibrium constants were determined: Ks0 =[HA]?(pKs0 3.44), Ks1 =[H2A+]/[H3O+](pKs1 0.61), and Ks2 =[A-][H3O+](pKs2 15.04).
A model study of epothilone synthesis: An alternative synthetic approach to the C1-C7 fragment
Authors: Lalic Gojko , Galonic Danica , Matovic Radomir , Saicic Radomir
Published: August 2005

In this model study an alternative synthetic approach to the C1?C7 fragment of epothilones was investigated. Starting from 4,4-dimethylcyclopentenone, a 7 step reaction sequence afforded the key intermediate 7 in 27% overall yield. Surprisingly, the attempted deprotection of latent functionalities in 7 failed, indicating the incompatibility of the ethoxyethyl protective group with the reaction conditions employed.
The growth and optical properties of Bi12SiO20 single crystals
Authors: Golubovic Aleksandar , Nikolic Slobodanka , Gajic Rados , Djuric Stevan , Valcic Andreja
Published: August 2005

Single crystals of Bi12SiO20 were grown from the melt by the Czochralski technique. The critical crystal diameter dc=10 mm and the critical rate of rotation ?c=20 rpm were calculated by equations from the hydrodynamics of a melt. The rate of crystal growth was experimentally obtained to be 5 mm/h. The crystal growth was in the [111] direction. The lattice parameter a=1.0096nm was determined by X-ray powder diffraction. The reflectance spectra were recorded in the wave numbers range 20?5000 cm-1 at different temperatures. For all the recorded spectra the values of the vibrational TO and LO modes were found using the Kramers-Kronig analysis (KKA). Twentyfive TO and LO modes were found at 70 K, and eighteen at 295 K. The obtained results are discussed and compared with published data.
The growth of Nd: YAG single crystals
Authors: Golubovic Aleksandar , Nikolic Slobodanka , Gajic Rados , Djuric Stevan , Valcic Andreja
Published: August 2005

Y3Al5O12 doped with 0.8%wt.Nd (Nd:YAG) single crystals were grown by the Czochralski technique under an argon atmosphere. The conditions for growing the Nd:YAG single crystals were calculated by using a combination of Reynolds and Grashof numbers. The critical crystal diameter and the critical rate of rotation were calculated from the hydrodynamics of the melt. The crystal diameter Dc=1.5 cm remained constant during the crystal growth while the critical rate of rotation changed from ?c=38 rpm after necking to ?c=13 rpm at the end of the crystal. The value of the rate of crystal growth was experimentally found to be 0.8?1.0 mm/h. According to our previous experiments, it was confirmed that 20 min exposure to conc. H3PO4 at 603 K was suitable for chemical polishing. Also, one-hour exposure to conc. H3PO4 at 493 K was found to be suitable for etching. The lattice parameter a=1.201 (1) nm was determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.
The temperature dependence of the disproportionation reaction of iodous acid in aqueous sulfuric acid solutions
Authors: Markovic Smiljana , Rakicevic Novica , Misljenovic Djuro
Published: August 2005

The aim of this work was to examine the disproportionation reaction of iodous acid, HOIO, in aqueous 0.18 mol/dm3H2SO4 solution, by spectrophotometric measurements of the absorbance. The absorbing HgI+-ion species were generated during the observed disproportionation process. The specific rate constants of disproportionation were calculated in the temperature range from 12 to 30 ?C. The average values ranged from 1.20 to 2.94 mol-1dm3 s-1, respectively. In addition, the values of the activation energies were determined by a graphical method. An average value of 71.20 kJ/mol was found for the chosen temperature interval.
Preparation and characterization of facial and meridional isomers of uns-cis-(ethylenediamine-N, N'-di-3-propionato)(S-arginine)cobalt(III) chloride dihydrate
Authors: Djinovic Vesna , Sabo Tibor
Published: August 2005

Both theoretically possible geometrical isomers, facial and meridional, of uns-cis-(ethylenediamine-N,N?-di-3-propionato)(S-arginine)cobalt(III) chloride dihydrate were prepared by the reaction of sodium uns-cis-(ethylenediamine-N,N?-di-3-propionato)( carbonato)cobaltate(III) with S-arginine at 75 ?C. The complexes were isolated chromatographically and characterized by elemental analysis as well as electron absorption and infrared spectroscopy.
The analysis of the kinetics of extraction of resinoids and hypericines from the amber, Hypericum perforatum L
Authors: Smelcerovic Andrija , Djordjevic Sinisa , Lepojevic Zika , Velickovic Dragan
Published: August 2005

The kinetics of the extraction of the overall extracted materials (resinoids), total hypericine, hypericine and pseudohypericine from amber (Hypericum perforatum L) was investigated by the procedure of maceration both with and without ultra-sound, using methanol as the extractant. It was found that the period of fast extraction with intensification of the extraction of resinoid by ultra-sound was significantly shorter (about 20 minutes) than was needed for the extraction without ultra-sound (about 5 h). Similar results were also obtained for the extraction of the other tested substances. It can be concluded that better drug exploitation can be achieved in a much shorter extraction time by intensification of the extraction using ultra-sound. By preparation of herbal material through pulverization, a significant grade of herbal tissue structure disintegration was achieved, so that turbulent mass transfer plays a dominant role in the extraction. The results show that the coefficient values of fast extraction (b) are approximately the same for all the investigated kinetics.
Synthesis of monoketo and monohydroxy eicosanoic acids and esters with substituents at odd-numbered (3-13) carbons
Authors: Çelik Hulya
Published: August 2005

In this study, monoketo and monohydroxy eicosanoic acids and their methyl esters with the position of the substituent on odd numbered carbon atoms from 3 to 13 were synthesized with high purity. Furthermore, the semicarbazone and anilide derivatives of the obtained keto acids were prepared. They were characterized by TLC, IR and 1H-NMR spectroscopy and their physical and chemical properties were established.
Influence of the stationary and mobile phase composition on solvent strength parameter εº and SP system parameter in NP column chromatography
Authors: Janjic Tomislav , Vuckovic Gordana , Celap Milenko
Published: August 2005

It is shown that SP system parameters, previously used for the linearization of log k values in RP chromatography, can also be used in NP chromatography. Avery good linear correlation between SP parameter and the earlier described Snyder solvent strength parameter has been established. It was also found that the phase equilibrium constant K is independent of the polarity and concentration of the more polar component of binary solvent mixtures.
Extraction and separation of titanium(IV) with D2EHPA and PC-88A from aqueous perchloric acid solutions
Authors: Singh Rajeev , Dhadke Purshottamm
Published: August 2005

The liquid-liquid extraction of Ti(IV) from perchlorate media using di(2-ethylhexyl) phosphoric acid (D2EHPA) and 2-ethylhexyl prosphonic acid mono-2-ethylhexyl ester (PC-88A) in toluene as the extractant was studied Quantitative extraction of Ti(IV) was observed in the lower acidity range of 0.01 to 0.1 mol dm-3 with 0.003 mol dm-3 D2EHPA and 0.01 mol dm-3 PC-88A in toluene, respectively, and in the higher acidity range of 9.0 to 10.0 mol dm-3 with 0.1 mol dm-3 D2EHPA and PC-88A in toluene. Ti(IV) was completely stripped from the metal loaded organic phase of both the extractants with 3%H2O2 in 1M H2SO4 and determined spectrophotometrically. The stoichiometry of the extracted species was determined on the basis of slope analysis. The extraction in the lower acidity range was found to proceed by a cation-exchange mechanism with the extracted species being TiOR2.2HR while in the higher acidity range it was by solvation with the extracted species being Ti(OH)3ClO4.4HR. Separation of Ti(IV) was also carried out from some associated metals like Fe(III), Al(III), V(V), Ce(IV), Mg(II) and Mn(II). The developed methods were extended for the determination of Ti(IV) in real samples like ilmenite, magnetite and red mud in order to show the practical utility of the extractants.
Synthesis and characterization of 2,3,13,14-tetramethyl (ethyl or p-tolyl)- 1,4,12,15-tetraazacyclodocosa-1,3,12,14-tetraene complexes of Mg(II), Ca(II), Sr(II) and Ba(II)
Authors: Prasad Raghu , Gupta Seema
Published: August 2005

2+2 Cyclocondensation of 1,7-diaminoheptane with ?-diketones, viz 2,3-butanedione, 3,4-hexanedione or 4,4?-dimethylbenzil, in the presence of Mg2+, Ca2+, Sr2+ and Ba2+ ions as templates yields a series of complexes of the type [ML(X2)](where L = N4 macrocycle having a 22-membered ring and X=Cl or NCS). The resulting complexes were characterized by elemental analysis conductance measurements and IR and 1H-NMR spectral studies.
Excess molar volume of the acetonitrile + alcohol systems at 298.15K. Part I: Density measurements for acetonitrile + methanol, + ethanol systems
Authors: Grguric Ivona , Tasic Aleksandar , Djordjevic Bojan , Kijevcanin Mirjana , Serbanovic Slobodan
Published: August 2005

The excess molar volume VE of the binary liquid systems acetonitrile methanol and acetonitrile + ethanol has been evaluated from density measurements at 298.15K and at atmospheric pressure over the entire composition range. A vibrating tube densimeter, type Anton Paar DMA 55, was applied for these measurements. The Redlich?Kister equation was used to fit the experimental VE data.
Cu(II) complexes with a pendant octaazamacrocycle and µ-bonded aromatic carboxylates
Authors: Vuckovic Gordana , Antonijevic Mirjana , Poleti Dejan
Published: August 2005

Three new cationic mixed-ligand Cu(II) complexes with N,N?,N??,N???-tetrakis(2-pyridylmethyl)- 1,4,8,11-tetraazacyclotetradecane (tpmc) and bridging aromatic mono- or dicarboxylate ligands were prepared. Elemental analysis, conductometric and magnetic measurements, as well as electronic and IR spectroscopy were employed for their characteriization. It is proposed that the complexes [Cu2(C6H5COO)tpmc](CIO4)3MeOH and [Cu2(Hpht)tpmc](CIO4). 3H2O(H2pht=phthalic acid) are binuclear with ?-coordination of the carboxylate monoanions. The third complex [Cu4ipht(tpmc)2](CIO4)6NaClO42MeCN (H2ipht=isophthalic acid) is one of the rare tetranuclear Cu(II)-tpmc complexes with an aromatic dicarboxylate ion bridging two Cu2tpmc units. This was also confirmed by preliminary results of the determination of the crystal structure.
Immobilization of Na, K-ATPase isolated from rat brain synaptic plasma membranes
Authors: Momic Tatjana , Vujcic Zoran , Vasic Vesna , Horvat Anica
Published: August 2005

Rat brain Na,K-ATPase partially purified by SDS from synaptic plasma membranes (SPM) was immobilized by adsorption on nitrocellulose (NC) polyvinylidene fluoride (PVDF) and glass fiber (GF) membranes. Partial SDS solubilization increased the enzyme activity by 40%. With regard to the preservation of the enzyme activity, nitrocellulose was shown to be the optimal support for the immobilization. The enzyme showed the highest percentage activity (14%) after 30 min of SPM adsorption, at 20?C under the vaccum, with 25 ?g of proteins per NC disc filter. In addition adsorption on NC stabilizes the Na,K-ATPase, since the activity was substantial 72 h after adsorption at 20?C. After adsorption, the sensitivity of the enzyme to HgCl2 and CdCl2 inhibition was higher. The results show that immobilized Na,K-ATPase SPMcan be used as a practical model for the detection of metal ions in different samples.
Quantitative evaluation of iPP nucleation in the presence of carbon fibres: Induction time approach
Authors: Grozdanov Anita , Bogoeva-Gaceva Gordana , Avella Maurizio
Published: August 2005

Crystallization and nucleation behavior in model composites based on iPP and differently sized carbon fibres have been analyzed in this work. The investigations were performed in the isothermal regime (120?127 ?C) using PLM and DSC. The results were analyzed by applying the Avrami and Muchova-Lednicky methods. It was shown that the carbon fibre surface acts as a nucleating agent during the crystallization of the iPP matrix. The highest effect was obtained with the fibres of PP-compatible size (C-T) related to unsized carbon fibres (C-U). The induction time, ti, and half-time of crystallization decreased with increasing carbon fibre content. The energy effect on the thickness of the critical nucleus decreased in the presence of C-fibres, a fact confirmed by a decrease in the nucleation parameter Q and the difference energy parameter ?? (Q decreased from ? 4.96 for iPP to ?21.32 for C/iPP model composites, and ?? decreased from 6.14x10-7 J/cm2 for iPP to 1.63x10-7 J/cm2 for model composites). The results of the model composites and their comparison with published data confirmed that the Muchova-Lednicky method could be successfully applied for the quantitative evaluation of the nucleation parameters not only in the temperature range previously suggested (130?138?C), but also at lower crystallization temperatures (Tc=121?127?C).
The representative particle of copper powder and branch of copper dendrites
Authors: Popov Konstantin , Nikolic Nebojsa , Rakocevic Zlatko
Published: August 2005

Electrochemically deposited copper powders, which are formed of particles of different size and morphology, are characterized by some properties like specific surface and apparent density. Aprocedure of the determination of a representative powder particle, exhibiting the same values of specific surface and apparent density as the powder is proposed. The proposed procedure also permints an explanation of the branching of copper dendrites.
Structure and stereochemistry of electrochemically synthesized poly-(l-naphthylamine) from neutral aceto- nitrile solution
Authors: Ciric-Marjanovic Gordana , Marjanovic Budimir , Stamenkovic Vojislav , Vitnik Zeljko , Antic Vesna , Juranic Ivan
Published: August 2005

Poly-(1-naphthylamine) films were synthesized potentiodinamically and potentiostatically from 1-naphthylamine in neutral acetonitrile medium using a platinum electrode. These polymer films were investigated by infrared spectroscopy. Contrary to earlier published results neglecting the stereochemistry of the poly-(1-naphthylamine), we predict on the basis of quantum stereochemical analysis of the possible structural subunits of the polymer, that the ordinary N?C(4) coupled product is not predominant in the polymer because it is far removed from the expected planarity. Based on the results of IR investigations and semiempirical quantum chemical calculations, it is proposed that the polymer products are formed via mixed N?C(4), N?C(5) and N?C(7) coupling routes. The heats of formation of the oxidized 1-naphthylamine dimers and hexamers were calculated.
Excess molar volume of acetonitrile + alcohol systems at 298. 15 K. - Part II: Correlation by cubic equation of state
Authors: Grguric Ivona , Kijevcanin Mirjana , Djordjevic Bojan , Tasic Aleksandar , Serbanovic Slobodan
Published: August 2005

The excess molar volume VE of the binary liquid systems acetonitrile methanol and acetonitrile + ethanol, experimentally determined in the previous part, were correlated by the PRSV CEOS coupled with the vdW and TCBT mixing rules. The results obtained show that the number and position of the interaction parameters of these models are of great importance for a satisfactory fitting of VE data.
Normal and reversed phase thin-layer chromatography of new 16, 17-secoestrone derivatives
Authors: Acanski Marijana , Jovanovic-Santa Suzana , Jevric Lidija
Published: August 2005

The retention behavior and separation ability of a series of new 16,17-secoestrone derivatives has been studied on silica gel, alumina and C-18 silica gel layers with non-aqueous and aqueous-organic mobile phases. The retention behavior and separation ability are discussed in terms of the nature of the solute, eluent and stationary phase.
Sulfur retention by ash during coal combustion - Part I: A model of char particle combustion
Authors: Ilic Mladen , Grubor Borislav , Manovic Vasilije
Published: August 2005

A model for the combustion of porous char particles as a basis for modeling the process of sulfur retention by ash during coal combustion is developed in this paper. The model belongs to the microscopic intrinsic models and describes the dynamic behavior of a porous char particle during combustion taking into account temporal and spatial changes of all important physical properties of the char particle and various combustion parameters. The parametric analysis of the enhanced model shows that the model represents a good basis for the development of a model for the process of sulfur retention by ash during coal combustion. The model enables the prediction of the values of all parameters necessary for the introduction of reactions between sulfur compounds and mineral components in ash, primarily calcium oxide.
Oil pollutants in alluvial sediments: Influence of the intensity of contact with ground waters on the effect of microorganisms
Authors: Solevic Tatjana , Jovancicevic Branimir , Vrvic Miroslav , Wehner Hermann
Published: August 2005

The influence of the intensity of interaction between oil pollutants and ground waters in alluvial sediments on the effect of microbial activity was investigated in this work. The study was based on a comparison of detailed analyses of two fractions of an oil pollutant originating from a Danube alluvial formation near the Pancevo Oil Refinery: fraction 1, separated from the aqueous layer by decantation, presumed to have been in less intensive interaction with water, and fraction 2, isolated from the aqueous emulsion by extraction with chloroform, presumed to have been in stronger interaction with water. Both fractions were shown to originate from the same type of oil pollutant. Nevertheless, significant compositional differences between the two fractions were observed. Asignificantly pronounced domination of even carbon number homologues of C18?C24 n-alkanes in fraction 2, atypical for crude oil pollutants, compared to the corresponding distribution observed in fraction 1, suggested a more intense activity, i.e., a much better effect of microorganisms in direct contact with the oil pollutant within the aqueous environment. The identification of even carbon number C14?C18 n-alcohols and C14?C18 fatty acids, as well as cholesterol, in fraction 2, suggested that microorganisms of the algal type in non-photosynthetic conditions were most probably responsible for the mentioned microbial processes.
A stilbene from the heartwood of Maclura pomifera: Note
Authors: Djapic Nina , Djarmati Zoltan , Filip Snezana , Jankov Ratko
Published: August 2005

Dried heartwood powder of Maclura pomifera, Moraceae, was extracted with acetone. Silica gel column chromatography (CC) of the crude extract yielded 2',3',4',5'-tetrahydroxystilbene (oxyresveratrol).
Composition of the lipophilic extract from the sponge Suberites domuncula
Authors: de Rosa , Iodice Carmine , Nechev Jordan , Stefanov Kamen , Popov Simeon
Published: August 2005

The composition of the lipophylic extract from the sponge Suberites domuncula was investigated. Lipids and their fatty acids, as well as volatile compounds and sterols were identified. Stanols are the main class of steroids in the investigated sponge. A high concentration of unsaturated long chain fatty acids (C26?C28) was identified. The presence of branched and odd fatty acids indicates associated bacteria in the sponge.
Structural studies on metallobleomycins: The interaction of Pt(II) and Pd(II) with bleomycin
Authors: Papakyriakou Athanasios , Bratsos Ioannis , Katsaros Nikos
Published: August 2005

Two of the most successful chemotherapeutic agents used in the treatment of several neoplasias are bleomycin and cisplatin. Both drugs attack the DNA leading to the cancer cells death via different mechanisms. In view of the fact that the combination with each other leads to enhanced activity with less sever side effects, we have undertaken NMR studies on the complexes formed between bleomycin and PtII, PdII, cisplatin and transplatin. Herein we present a brief review of the studies on metallobleomycins which were carried out by our lab and others, as an outline of the results obtained using NMR in combination to circular dichroism spectroscopy. Our data indicate that in most cases and under several conditions studied, both metal ions form similar complexes with BLM while more than one species are present in the solution. Structural implications and comparisons with other metallobleomycins are being discussed. .
Regiospecificty in the heterocyclization of β-oxonitriles to 5-substituted 4-oxothiazolidine derivatives
Authors: Markovic Rade , Dzambaski Zdravko , Stojanovic Milovan , Steel Peter , Baranac Marija
Published: August 2005

Astudy on the regiospecificity of the base-catalyzed reaction of activated ?-oxonitriles 1 with diethyl mercaptosuccinate affording the title compounds 3 is reported. Other competitive heterocyclic products, that is 4-oxo-1,3-thiazinanes 4, derivatives of tetrahydrothiophene 5 and/or thiacyclohexane 6 which on the grounds of mechanistic considerations could be formed, were not observed. Spectroscopic and experimental evidence together with theoretical considerations, provides a reasonable explanation for the observed regiospecificity.
Algebraic structure count of liner phenylenes and their congeners
Authors: Gutman Ivan
Published: August 2005

The algebraic structure count of the linear phenylene with h six-membered rings is known to be equal to h + 1. We show that the same expression applies if each four-membered ring in the phenylene is replaced by a linear array consisting of k four-membered rings, where k = 4, 7, 10,... For any other value of k, the algebraic structure count is either 0 or 1 or 2, and does not increase with increasing h.
FTIR study of carbon monoxide adsorption on ion-exchanged X, Y and mordenite type zeolites
Authors: Rakic Vesna , Dondur Vera , Hercigonja Radmila
Published: August 2005

In this work Fourier transform infrared (FTIR) study has been applied to study the adsorption of carbon monoxide on transition metal (Mn2+, Co2 Ni2+) ion-exchanged zeolites type Y, X and mordenites. The adsorption of CO at room temperature produces overlapping IR absorption bands in the 2120?2200 cm-1 region. The frequency of the band around 2200 cm-1 is found to be dependent not only on the charge-balancing transition metal cation but also on the framework composition. The frequencies of the band near 1600 cm-1 was found to be dependent on the Si/Al ratio of the investigated zeolites.
Termplate synthesis of Mn(II) complexes of tetraazamacrocycles derived from diaminoalkanes and 3, 4-hexanedione or benzil
Authors: Prasad Raghu , Gupta Nitin
Published: August 2005

Template condensation of ?-diketones, such as 3,4-hexanedione or benzil with 1,n-diaminoalkanes (where n = 4, 5, 6, 7, 8, 9, 10 or 12) in the presence of Mn(II) resulted in the formation of complexes of the type [MnL(NO3)]NO3 (where L = 16 to 32-membered macrocycle). These complexes have been characterized by elemental analyses, conductances, magnetic measurements, as well as IR and electronic spectra.
Saturated-liquid heat capacity: New polynomial models and review of the literature experimental data
Authors: Jovanovic Jovan , Grozdanic Dusan
Published: August 2005

In this paper a review of selected literature experimental data for saturated-liquid heat capacities was presented. Two-, three- and four-parameter polynomial correlation models are tested on those data. Obtained results lead to the conclusion that correlation quality depends on the number of parameters, and slightly on the type of models. The best two three- and four-parameter models were proposed.
Preparation of basalt-based glass ceramics
Authors: Matovic Branko , Boskovic Snezana , Logar Mihovil
Published: August 2005

Local and conventional raw materials?massive basalt from the Vrelo locality on Kopaonik mountain?have been used as starting materials to test their suitability for the production of glass-ceramics. Crystallization phenomena of glasses of the fused basalt rocks were studied by X-ray phase analysis optical microscopy and other techniques. Various heat treatments were used and their influences, on controlling the microstructures and properties of the products were studied with the aim of developing high strength glass-ceramic materials. Diopside CaMg(SiO3)2 and hypersthene ((Mg,Fe)SiO3) were identifies as the crystalline phases. The final products contained considerable amounts of a glassy phase. The crystalline size was in range of 8?480 ?m with plate or needle shape. Microhardness, crashing strength and wears resistence of the glass-ceramics ranged from 6.5?7.5, from 2000?6300 kg/cm2 and from 0.1?0.2 g/cm, respectively.
Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes
Authors: Valentic Natasa , Uscumlic Gordana
Published: August 2005

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.
Kinetics and mechanism of cetyltrimethylammonium bromide catalyzed oxidation of diethylene glycol by chloramine-T in acidic medium
Authors: Bhagwat V.W. , Tiwari J. , Choube A. , Pare B.
Published: August 2005

The kinetics and mechanism of the C16TABcatalyzed oxidation of diethylene glycol (2,2?-oxydiethanol) by chloramine-T in acidic medium has been studied. The reaction has a first-order dependence on chloramine-T. With excess concentrations of other reactants, the reaction rate follows fractional order kinetics with respect to [diethylene glycol]. The micellar effect due to cetyltrimethylammonium bromide, a cationic surfactant, has been studied. The reaction is catalyzed by chloride ions as well. The small salt effect and increase in the reaction rate with increasing dielectric constant suggest the involvement of neutral molecules in the rate determining step. Addition of p-toluenesulfonamide retards the reaction rate. On the basis of product analysis, a pertinent mechanism is proposed.
Investigation of the compatibility between one-dimensional system parameters and the multidimensional solvation parameter model in RP liquid column chromatography
Authors: Janjic Tomislav , Vuckovic Gordana , Celap Milenko
Published: August 2005

It has been established that in many cases the system constants used in the Solvation parameter model as well as the corresponding log k values can be linearized in the same NSP and NSP?scale, respectively, which shows the compatibility of both models. NSP and NSP?are one-dimensional system parameters adapted to the chromatographic system used over the phase equilibrium constant.
Energy storage in the photosynthetic electron-transport chain: An analogy with Michaelis-Menten kinetics
Authors: Markovic Dejan
Published: August 2005

Simultaneous measurements of fluorescence and thermal emission have been performed by applying combined fluorescence and photoacoustic techniques on isolated thylakoids pretreated by prolonged illumination with saturating light. The traces were used to create Lineweaver-Burk type plots, proving clearly at least a formal analogy between the kinetics of the mechanisms governing fluorescence and thermal emission from isolated thylakoids and Michaelis-Menten kinetics of enzymatic reactions. Two characteristic parameters were calculated from them (energy storage and half-saturation light intensity) in order to obtain a basic, initial response of the photosynthetic apparatus functioning under photoinhibition stress.
Spectrophotometric determination of ajmaline and brucine by Folin Ciocalteu’s reagent
Authors: Singh Dhruv , Srivastava Bhavana , Sahu Archana
Published: August 2005

Arapid and simple spectrophotometric procedure is described for the determination of ajmaline and brucine. The method is based on the development of blue colored product due to reduction of tungstate and/or molybdate in Folin Ciocalteu?s reagent (FCR) by ajmaline and brucine in alkaline medium. The color is stable for more than 48 h. The chromogenic reaction has ?max at 540 nm with molar absorptivity 1.64 x 104 and 2.37 x 103 l mol-1 cm-1 in the Beer?s law range 1?8 ?g ml-1 and 10?100 ?g ml-1 for ajmaline and brucine, respectively.
Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 1, 3-bis-substituted-5, 5-dimethylhydantoins
Authors: Uscumlic Gordana , Kshad Abdulbaseta , Mijin Dusan
Published: August 2005

A series of 1,3-bis-substituted-5,5-dimethylhydantoins was synthesized using the reaction of 5,5-dimethylhydantoin with the corresponding alkyl halide in the presence of trimethylamine as catalyst and sodium hydroxide, according to a modified literature procedure. The experimental investigation included modification of the synthetic procedure in terms of starting materials solvent, temperature, isolation techniques, as well as purification and identification of the products. The absorption spectra of the 1,3-bis-substituted-5,5-dimethylhydantoins were recorded in twelve solvents in the range 200?400 nm. The effects of the solvent polarity and hydrogen bonding on the absorption spectra were interpreted by means of linear solvation energy relationships using a general equation of the form ? = ?0 s?* + a? + b? and by two-parameter models presented by the equation ? = ?0 s?* + a?, where ?* is a measure of the solvent polarity/polarisability, ? is the scale of the solvent hydrogen bond donor acidities and ? is the scale of the solvent hydrogen bond acceptor basicities. The solvent and substituent effects on the electronic absorption spectra of the investigated hydantoins is discussed.
Vitamin B12-catalyzed synthesis of some peracetylated alkyl β-D-xylopyranosides
Authors: Petrovic Zorica , Andjelkovic Dejan , Stevanovic Ljiljana
Published: August 2005

The vitamin B12-catalyzed glycosylation reaction of brominated ?-D-xylose peracetate with alkanols ROH (C1-C8) has been studied. The catalytically active species in this reaction was cob(I)alamin, obtained by chemical reduction of Vitamin B12 with NaBH4 (Co(III) to Co(I)). The reaction was carried out with 2 mol% of vitamin B12, with respect to xylosyl bromide 1 under argon at room temperature. Under these conditions, peracetylated C1-C8-alkyl ?-D-xylopyranosides (3a?3f) were obtained in moderate yield (55?70 %). In all cases 3,4-di-O-acetyl-D-xylal (4) was obtained, as the product of reductive elimination of peracetylated xylosyl bromide (15?25 %).
The effect of the particle shape and structure on the flow ability of electrolytic copper powder II: The experimental verification of the model of the representative powder particle
Authors: Popov Konstantin , Pavlovic Miomir , Pavlovic Ljubica , Ivanovic Evica , Krstic Snezana , Obradovic Milutin
Published: August 2005

An analysis of the effects of the shape, surface structure and size distribution of particles on the flow ability of the copper powder was performed. It is shown that the most important property of the particles of a powder, regarding the flow ability of the powder, is the surface structure of the particles.
Oxidative fragmentation of 5-hydroxy-1-oxo-5α-cholestan-3β-yl acetate
Authors: Krstic Natalija , Bjelakovic Mira , Lorenc Ljubinka , Pavlovic Vladimir
Published: August 2005

5-hydroxy-1-oxo-5?-cholestan-3?-yl acetate (11) was prepared in 5 steps starting from (E)-3?-acetoxy-5,10-seco-1(10)-cholesten-5-one (6). Treatment of the 1-oxo-5-hydroxy derivative 11 with lead tetraacetate (LTA) (under thermal or hypoiodite conditions) or with mercuric oxide/iodine (HgO/I2) reagent resulted in the oxidative ?-fragmentation of the C(5)?C(10) bond affording 1,5-dioxo-5,10-secocholest-10(19)-en-3?-yl acetate (12), in different yields, depending on the reagent. Also the stereochemistry of the 1?,6?-cyclization product 13, formed by transannular cyclization of the 1,5-diketone 12 on silica gel, is discussed in this work.
Gas chromatographic retention indices for N-substituted amino s-triazines on capillary columns. Part V. Temperature dependence of the retention index
Authors: Mijin Dusan , Antonovic Dusan , Jovanovic Bratislav
Published: August 2005

The temperature dependence of the retention index was studied for N-substituted amino s-triazines on DB-1, DB-5 and DB-WAX capillary columns within the temperature range 190?230 ?C. Two linear equations with the column temperature and its reciprocal as variables were studied. The first one shows a slightly better precision for 2,4-bis(alky lamino)-6-chloro-s-triazines and 2-alkylamino-4,6-dichloro-s-triazines while the second one shows a better precision for 2,4-bis(cycloalkylamino)-6-chloro-s-triazines.
Electrochemical oxidation of methanol on Pt3Co bulk alloy
Authors: Gojkovic Snezana
Published: August 2005

The electrochemical oxidation of methanol was investigated on a Pt3Co bulk alloy in acid solutions. Kinetic parameters such as transfer coefficient reaction orders with respect to methanol and H+ ions and energy of activation were determined. It was found that the rate of methanol oxidation is significantly diminished by rotation of the electrode. This effect was attributed to the diffusion of formaldehyde and formic acid from the electrode surface. Stirring of the electrolyte also influenced the kinetic parameters of the reaction. It was speculated that the predominant reaction pathway and rate determining step are different in the quiescent and in the stirred electrolyte. Cobalt did not show a promoting effect on the rate of methanol oxidation on the Pt3Co bulk alloy with respect to a pure Pt surface.
High-performance liquid chromatographic determination of famotidine in human plasma using solid-phase column extraction
Authors: Zendelovska Dragica , Stafilov Trajce
Published: August 2005

A rapid, specific and sensitive high-performance liquid chromatographic method for the determination of famotidine in human plasma has been developed. Famotidine and the internal standard were chromatographically separated from plasma components using a Lichrocart Lichrospher 60 RP select B cartridge for solid-phase separation with a mobile phase composed of 0.1 % (v/v) triethylamine in water (pH 3) and acetonitrile (92:8, v/v). UV detection was set at 270 nm. The calibration curve was linear in the concentration range of 10.0 ? 350.0 ng mL-1. The method was implemented to monitor the famotidine levels in patient samples.
The effect of the particle shape and structure on the flowability of electrolytic copper powder. III. Amodel of the surface of a representative particle of flowing copper powder electrodeposited by re
Authors: Popov Konstantin , Krstic Snezana , Obradovic Milutin , Pavlovic Miomir , Pavlovic Ljubica , Ivanovic Evica
Published: August 2005

The structure of the surface of copper powder particles is discussed and correlated with the lowest apparent density at which copper powder can still flow. It is shown that such structures can be easily obtained in the electrodeposition of powders in reversing current regimes.
Dynamic holdup in a countercurrent gas - flowing solids - packed bed contactors
Authors: Nikacevic Nikola , Dudukovic Aleksandar , Predojevic Zlatica
Published: August 2005

Equations for the prediction of the holdup of dynamic solids in countercurrent gas ? flowing solids ? packed bed contactors are presented in this paper. The correlations do not require the use of parameters that need to be determined by experimental measurements in the actual system of interest. They could be used for a wide range of operational conditions different packing types and a variety of flowing solids materials. The equations are compared with all available experimental data from the literature.
Scanning probe microscopy characterization of immobilized enzyme molecules on a biosensor surface: Visualisation of individual molecules
Authors: Losic Dusan , Short Ken , Gooding Justin , Shapter Joe
Published: August 2005

Scanning probe microscopy techniques were used to study immobilized enzyme molecules of glucose oxidase (GOD) on a biosensor surface. The study was carried out in order to optimize atomic force microscopy (AFM) imaging and reveal themolecular resolution of individual GOD molecules. Chemically modified AFM tips and the light tapping mode were found to be the optimal conditions for imaging soft biomolecules such as GOD. The information obtained from the AFM images included spatial distribution and organization of the enzyme molecules on the surface, surface coverage and shape, size and orientation of individual molecules. Two typical shapes of GOD molecules were found, spherical and butterfly, which are in accordance with the shapes obtained from scanning tunnelling microscopy (STM) images. Using a model of the orientation of the GOD molecules on the surface, these shapes are assigned to the enzyme standing and lying on the surface. After AFM tip deconvolution, the size of the spherical shaped GOD molecules was found to be 12 ?2.1 nm in diameter, whereas the butterfly shapes were 16.5 ? 3.3 nm x10.2 ? 2.5 nm. Corresponding STM images showed smaller lateral dimensions of 10 _1nm_ 6 ?1nm and 6.5 ? 1 nm x5 ? 1 nm. The disagreement between these two techniques is attributed to the deformation of the GOD molecules caused by the tapping process.
The synthesis and characterization of complexes of zinc(II), cadmium(II), platinum(II) and palladium(II) with potassium 3-dithiocarboxy-3-aza-5-amino-pentanoate
Authors: Leka Zorica , Grujic Slobodan , Tesic Zivoslav , Lukic Svetlana , Skuban Sonja , Trifunovic Srecko
Published: August 2005

Complexes of zinc(II), cadmium(II), platinum(II) and palladium(II) with a new polydentate dithiocarbamate ligand, 3-dithiocarboxy-3-aza-5-aminopentanoate (daap-), of the type M(daap)2.nH2O (M= Zn(II), Cd(II), n = 2, or M= Pt(II) Pd(II), n = 0), have been prepared and characterized by elemental analysis IR and UV/VIS spectroscopy, as well as magnetic measurements. The spectra of the complexes suggest a bidentate coordination of the daap- ligand to the metal ions via the sulfur atoms of the deprotonated dithiocarbamato group. The fact that under the same experimental conditions its S-methyl ester does not form complexes could be taken as proof of the suggested coordination mode.
The preparation and characterization of Cu(II) complexes with N, N’, N", N’’’-tetrakis(2-pyridylmethyl)-1, 4, 8, 11-tetraazacyclotetradecane and 2, 6-diacetylpyridine bis (semi/thiosemicarbazone)
Authors: Tanaskovic Sladjana , Vuckovic Gordana
Published: August 2005

Two new Cu(II) mixed-ligand complexes with octadentate N,N?,N",N?"-tetrakis 2-pyridylmethyl))-1,4,8,11-tetraazacyclotetradecane (tpmc) and potentially pentadentate ligands 2,6-diacetylpyridine bis(semicarbazone) (DAPsc2) or 2,6-diacetylpyridine bis(thiosemicarbazone) (DAPtsc2) were prepared. The general formulas: [Cu4DAPsc2(tpmc)2]ClO4)8. 5CH3COCH3. H2O and [Cu2 DAPtsc2(tpmc)](ClO4)4. 7C2H5OH were proposed on the basis of elemental analyses and conductometric measurements. The complexes were characterized by magnetic measurement, electronic absorption and IR spectroscopy. For the dinuclear complex, an exo coordination of Cu(II) with four nitrogens from tpmc and ?-bonded DAPtsc2 through sulfurs and possibly terminal hydrazinic (azomethine) nitrogens is assumed. For the tetranuclear complex, it is supposed that one DAPsc2 bridges two [Cu2tpmc]4+ units using oxygens and terminal hydrazinic nitrogens as ligators. Finally, some antibacterial activity of the complexes was found.
Spectroscopic, magnetic and thermal behaviour of the 2, 3, 4-trimethoxybenzoates of heavy lanthanides(III) and yttrium(III)
Authors: Ferenc Wieslawa , Bocian Beata , Walkow-Dziewulska Agnieszka
Published: August 2005

The complexes of 2,3,4-trimethoxybenzoic acid with Tb(III), Dy(III), Ho(III) Er(III), Tm(III), Yb(III), Lu(III) and Y(III) are crystalline, anhydrous salts with colours typical of the M(III) ions. The carboxylate group is probably a bidenate, chelating ligand. The thermal stabilities of the complexes were examined under an air atmosphere in the temperature range 293?1273 K. The solubility in water at 293 K for all the heavy lanthanide(III) and yttrium(III) complexes are in the order of 10-3 mol dm-3. The magnetic moments of the complexes were determined in the temperature range 77?300 K.
Geochemistry of the cretaceous-tertiary transition boundary at Blake Nose (N. W. Atlantic): Cosmogenic Ni
Authors: Premovic Pavle , Nikolic Nikola , Pavlovic Mirjana , Panov Katja
Published: August 2005

The Cretaceous-Tertiary (KT) boundary transition at the Blake Nose Plateau recovered by ODP Leg 171B (site 1049, hole A, core 17X, section 2) contains an ejecta bed (thickness ca. 17 cm) marking a late Cretaceous asteroid impact. The nature and geochemical composition of this bed imply that it originated mainly from the target rocks of the Chicxulub impact site (Yucatan Peninsula, Mexico), the site of the presumed asteroid impact. The ejecta bed of hole 1049A contains relatively high concentrations of Ni (up to 165 ppm) within the carbonate fraction. It is reasoned that this enhancement represents a sudden and rapid air fall of high cosmogenic Ni into he Blake Nose Basin. The source of the metal was the Chicxulub impacting (carbonaceous) chondrite. It is suggested that many calcareous planktons in the KT ocean surface water of the Blake Nose Plateau were probably vulnerable to the high influx of superacid rainfall and associated toxic metals (e.g. Ni) created by the impact.
Saturated-liquid heat capacity of organic compounds: New empirical correlation model
Authors: Jovanovic Jovan , Grozdanic Dusan
Published: August 2005

A new saturated-liquid heat capacity model is recommended. This model is tested and compared with the known polynomial and quasi-polynomial models on 39 sets with 1453 experimental heat capacity data. The obtained results indicate that the new model is better then the existing models, especially near the critical point.