Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Cs. Novák is active.

Publication


Featured researches published by Cs. Novák.


Journal of Thermal Analysis and Calorimetry | 2002

Thermal Behavior of Paracetamol-Polymeric Excipients Mixtures

F. Giordano; A. Rossi; Ruggero Bettini; A. Savioli; A. Gazzaniga; Cs. Novák

The thermal behavior of binary mixtures of paracetamol and a polymeric excipient (microcrystalline cellulose, hydroxypropylmethylcellulose and cross-linked poly(vinylpyrrolidone)) was investigated. The physical mixtures, ranging from 50 to 90% by mass of drug, were submitted to a heating-cooling-heating program in the 35–180°C temperature range. Solid-state analysis was performed by means of differential scanning calorimetry (DSC), hot stage microscopy (HSM), micro-Fourier transformed infrared spectroscopy (MFTIR), and scanning electron microscopy (SEM).The polymeric excipients were found to address in a reproducible manner the recrystallization of molten paracetamol within the binary mixture into Form II or Form III. The degree of crystallinity of paracetamol in the binary mixtures, evaluated from fusion enthalpies during the first and second heating scans, was influenced by the composition of the mixture, the nature of the excipient and the thermal history. In particular, DSC on mixtures with cross-linked poly(vinylpyrrolidone) and hydroxypropylmethylcellulose with drug contents below 65 and75%, respectively, evidenced the presence only of amorphous paracetamol after the cooling phase. Microcrystalline cellulose was very effective in directing the recrystallization of molten paracetamol as Form II.


Journal of Thermal Analysis and Calorimetry | 2002

Effect of Molecular Mass on the Melting Temperature, Enthalpy and Entropy of Hydroxy-Terminated PEO

P.J. Sánchez-Soto; J. M. Ginés; M. J. Arias; Cs. Novák; A. Ruiz-Conde

This paper studies the effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated poly(ethylene oxide) (PEO). It aims to correlate the thermal behaviour of PEO polymers and their variation of molecular mass (MW). Samples ranging from 1500 to 200,000 isothermally treated at 373 K during 10 min, were investigated using DSC and Hot Stage Microscopy (HSM). On the basis of DSC and HSM results, melting temperatures were determined, and melting enthalpies and entropies were calculated. Considering the melting temperatures, it was found that the maximum or critical value of MW was found around 4000, and then these remain almost constant. This behaviour was interpreted assuming that lower MW fractions (MW<4000) crystallize in the form of extended chains and higher MW fractions (MW>4000), as folded chains. The melting enthalpies showed a scattering effect at least up to MW 35,000. It was difficult to obtain any relationship between melting enthalpies in J g−1 and MW. These variations seem to be of statistical nature. Corrected enthalpy data on a molar basis (kJ mol−1) exhibited a linear relationship with MW. Considering the solid—liquid equilibrium, the melting entropies (in kJ mol−1) were calculated. These values were more negative as compared with molar enthalpy increases. It was explained because the changes in melting temperatures are much smaller than those observed in the enthalpy values. Linear relationship between enthalpies andentropies as a function of MW was deduced.


Journal of Thermal Analysis and Calorimetry | 1990

Studies on the reactions of aluminium oxides and hydroxides

Cs. Novák; György Pokol; V. Izvekov; T. Gál

The hydrothermal and decomposition reactions of differently ground gibbsite and its reaction products were studied. The samples were treated isothermally under hydrothermal conditions or in air, and the products were characterized by thermogravimetry and IR spectroscopy. It was found that the method and duration of grinding and the particle size of the starting gibbsite influenced the reactivity of the gibbsite itself and that of the primary reaction products. In a later step of the reaction sequence (hydrothermal rehydration ofγ-alumina), the effects of the differences in the properties of the starting gibbsites were insignificant.ZusammenfassungEs wurden die hydrothermischen und Zersetzungsreaktionen verschiedener Gibbsitproben und deren Reaktionsprodukten untersucht. Die Proben wurden unter hydrothermischen Bedingungen oder in Luft isothermisch behandelt, die Produkte mittels TG und IR beschrieben. Es wurde festgestellt, da\ Art und Weise der Zerkleinerung und Korngrö\e des Gibbsit-Ausgangsmateriales die ReaktivitÄt von Gibbsit selbst, aber auch die der primÄren Reaktionsprodukte beeinflu\t. In spÄteren Schritten des Reaktionsverlaufes (hydrothermische Rehydratation von-Aluminiumoxid) besitzen Unterschiede in den Eigenschaften des Gibbsit-Ausgangsmateriales keinen Einflu\.


Journal of Thermal Analysis and Calorimetry | 2003

Composition and thermal stability of SiO2-based hybrid materials TEOS-MTEOS system

Maria Zaharescu; A. Jitianu; Ana Brăileanu; János Madarász; Cs. Novák; György Pokol

Hybrid materials with different amounts of organics permanently bound on the inorganic network obtained in the TEOS-MTEOS (tetraethoxysilan-methyltriethoxysilan) system are used for obtaining coatings with different optical and mechanical properties. To study the thermal stability of the mentioned materials, compositions with different molar ratios of the precursors were prepared. The influence of the solvent and water amounts on the gelation process was also investigated. The gels obtained were characterised by IR spectrometry and their decomposition temperatures were determined by DTA/TG. Thermal stability of the gels is rather influenced by their composition than the conditions of the gelation process.


Journal of Thermal Analysis and Calorimetry | 2002

Thermal And Structural Characterization of Commercial α-, β-, and γ-Cyclodextrins

G. P. Bettinetti; Cs. Novák; Milena Sorrenti

Abstractα-, β-, and γ-cyclodextrins (CDs) marketed by five different companies were characterized from the thermal and structural point of view. Three αCD samples showed two-step DSC dehydration profiles and their XRD patterns were characteristic for αCD⋅6H2O form I, whereas one brand with an apparent three-step DSC dehydration behaviour was a mixture of αCD⋅6H2O form I and anhydrous αCD. The differences in the DSC profiles after dehydration and EGA onset decomposition temperatures recorded for the five βCD brands were attributed to different manufacturing and purification processes. The five γCDs brands showed a common thermal behaviour and very similar XRD patterns. The patterns did not match the idealized pattern of γCD⋅14.1H2O, indicating the occurrence of two different hydrated crystal structures.


Journal of Thermal Analysis and Calorimetry | 1996

Thermal characterization of polyethylene glycols applied in the pharmaceutical technology using differential scanning calorimetry and hot stage microscopy

J. M. Ginés; M. J. Arias; A. M. Rabasco; Cs. Novák; Antonio Ruíz-Conde; P. J. Sánchez-Soto

In the present study, the effect of the molecular weight and thermal treatments on commercial polyethylene glycols (PEG) samples used in the pharmaceutical processing technology, has been analyzed using DSC and HSM. The molecular weight of these polymers range from 1500 to 200000. Thermal investigations on the melting behavior of original PEG samples (as received from the manufacturer) showed only one single melting DSC endotherm effect before 373 K. This fact was associated to the presence of only one type of polymeric chain. Using standard conditions, PEG samples were solidified from the melt at 373 K, either by flash cooling (using liquid nitrogen and an ice bath) and by slow cooling, soaked and by slow cooling at room temperature. They were further studied by DSC. It was found that after cooling, PEG with molecular weight 1500 and 15000 showed DSC thermograms with a single endothermic peak. However, thermograms for PEG 4000 and 6000 produced a splitted melting endotherm. This fact was attributed to the presence of two types of chains, that are the folded and extended chains.Ageing time influences also the shape of the DSC endothermal effects. It was concluded that the endotherms obtained after heating these PEG indicate that the thermal history determine the structure (extended or folded chain type forms) and the degree of crystallinity, as evidenced by changes in heat of fusion values, melting points and structures after crystallization. The relationships between melting enthalpies and melting points, as deduced from DSC diagrams, with molecular weight of the polymers are also presented.


Journal of Thermal Analysis and Calorimetry | 2001

Kinetic Analyis of TG Data XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine

J. Zsakó; György Pokol; Cs. Novák; Cs. Várhelyi; A. Dobó; G. Liptay

A number of 30 [Co(en)3 ]Y3 , [Co(en)2 X2 ]Y and [Co(en)2 X(amine)]Y2 type complexes (X =Cl, Br; Y =Cl, Br, I, NCO, NCS, NO3 , ClO4 , etc.; amine =aromatic and alkylamines) were obtained from trans-[Co(en)2 Cl2 ]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of [Co(en)3 ]Y3 complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)2 X2 ]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)2 X(amine)]Y2 type complexes one observes the formation of [Co(en)2 XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a non-linear kinetic compensation law was observed.


Journal of Thermal Analysis and Calorimetry | 2002

Calorimetric study of the effects of 2,4-dichlorophenol on the thermotropic phase behavior of DPPC liposomes

Á. Csiszár; A Bóta; Cs. Novák; E. Klumpp; G. Subklew

The effect of 2,4-dichlorophenol (DCP) on the main transition and pretransition of fully hydrated (20 mass%) dipalmitoylphosphatidylcholine (DPPC) multilamellar liposomes has been studied by differential scanning calorimetry (DSC). It was observed that an increase in the molar ratio of DCP/DPPC (from 4·10-5 up to 2·10-2) causes progressive reductions in the temperature and enthalpy of the pretransition. The higher concentration of DCP eliminates the pretransition. The influence of DCP on the main transition in this molar ratio range is not drastic, but a decrease in temperature and in the enthalpy values was observed. In the molar ratio range (from 2·10-1 up to 4·10-1) the DSC scans show multiple main transition peaks instead of the characteristic single peak of the main transition. Above a DCP/DPPC molar ratio of 0.6 a new peak appears at 25°C having about the same transition enthalpy as the main transition of the pure system.


Journal of Thermal Analysis and Calorimetry | 1999

Thermal stability of SiO2-based inorganic-organic hybrid materials

Maria Zaharescu; A. Jitianu; Ana Braileanu; V. Bãdescu; György Pokol; János Madarász; Cs. Novák

The hydrolysis-polycondensation of organically modified Si-alkoxides leads to the obtaining of inorganic-organic hybrid materials in which the organic moieties remain as permanent groups bonded to the inorganic network.The molecular species previously determinated by GC-MS during the gelation process have been significantly different according to the type of the alkoxide used.In the present work, thermal stability of SiO2-based inorganic-organic hybrid materials starting with TEOS (tetraethoxysilan), MTEOS (triethoxymethylsilan), VTEOS (triethoxyvinylsilan) and MTMOS (trimethoxymethylsilan) was studied.The molecular structure of the gels obtained determines differences in their thermal behaviour. Gels obtained starting with MTEOS show the highest thermal stability, while gels obtained using VTEOS the lowest, among the substituted alkoxides. A particular behaviour presents the gel obtained with MTMOS that decomposes in four steps. This could be explained by the presence in the gel of some prevalent types of molecular species with different thermal stability.


Journal of Thermal Analysis and Calorimetry | 1995

Thermal study of complex formation of triamterene with β-cyclodextrin by spray-drying and co-grinding

J. M. Ginés; M. J. Arias; Cs. Novák; P.J. Sánchez-Soto; A. Ruiz-Conde; E. Morillo

The formation of crystalline inclusion complex of triamterene with β-cyclodextrin (β-CD) was studied, evaluating the thermal behaviour and dispersion state of this drug in different types of binary systems. Spray-drying and co-grinding (oscillating mill) mixtures of triameterene with β-CD were prepared in 1∶1 molar ratio. The changes of crystalline properties of original (untreated) triamterene, β-CD, and composites obtained by co-grinding and spray-drying were investigated in comparison with those produced in simple physical mixtures. The thermal behaviour of the different samples was investigated using DTA. X-ray diffraction was applied as a complementary technique. The results have been explained by formation of amorphous drug particles on spray-drying samples and co-grinding or alternatively by means of a solid dispersion formation or a combination of these two. A contamination effect by grinding media was also observed as increasing grinding time.ZusammenfassungMittels Auswertung des thermischen Verhaltens und des Dispersions-zustandes der Droge bei verschiedenen Typen binärer Systeme wurde die Bildung kristalliner Einschlußkomplexe von Triamteren mit β-Cyclodextrin (β-CD) untersucht. In einem Molverhältnis von 1∶1 wurden sprühgetrocknete und kogemahlene (Oszillationsmühlen) Gemische von triamteren mit β-CD angefertigt. Die Änderungen der kristallinen Eigenschaften von Original-Triamteren (unbehandelt), β-CD und von Substanzen, die durch Komahlen und Sprühtrocknen erhalten wurden, wurden im Vergleich zu jenen in einfachen physikalischen Gemischen untersucht. Das thermische Verhalten der verschiedenen Proben wurde mittels DTA untersucht. Röntgendiffraktion wurde als eine zusätzliche Technik eingesetzt. Die Ergebnisse wurden mit der Bildung amorpher Drogenpartikel bei sprühgetrockneten Proben und mit Komahlen oder alternativ mit der Bildung einer festen Dispersion oder einer Kombination beider erklärt. Ein Verschmutzungseffekt beim Mahlen wurde ebenfalls beobachtet wie steigende Mahlzeit.

Collaboration


Dive into the Cs. Novák's collaboration.

Top Co-Authors

Avatar

György Pokol

Budapest University of Technology and Economics

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

J. Sztatisz

Budapest University of Technology and Economics

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

E. Morillo

Spanish National Research Council

View shared research outputs
Top Co-Authors

Avatar

P.J. Sánchez-Soto

Spanish National Research Council

View shared research outputs
Top Co-Authors

Avatar

Gy. Pokol

Budapest University of Technology and Economics

View shared research outputs
Top Co-Authors

Avatar

I. Eros

University of Szeged

View shared research outputs
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge