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Wyszukujesz frazę "Petkova, I." wg kryterium: Autor


Wyświetlanie 1-3 z 3
Tytuł:
Conformation-Dependent Photophysics of Bifunctional Hydrogen Bond Donor/Acceptor Molecules
Autorzy:
Kijak, M.
Petkova, I.
Toczek, M.
Wiosna-Sałyga, G.
Zielińska, A.
Herbich, J.
Thummel, R.
Waluk, J.
Powiązania:
https://bibliotekanauki.pl/articles/1814016.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.15.-e
02.70.-c
Opis:
A series of heteroazaaromatic molecules possessing both a hydrogen bond donor and acceptor groups linked by a single bond was studied using electronic absorption and fluorescence techniques, combined with quantum-chemical calculations. Fluorescence lifetimes and quantum yields strongly depend on the solvent. Double exponential decays are observed in alcohols. This was interpreted in terms of alcohol-induced syn-anti rotamerization in the ground electronic state. The driving force for the conformational change is provided by two factors: (a) solvent polarity increase; (b) the formation of two separate hydrogen bonds in the anti species. In the syn structure, formation of cyclic hydrogen bonds leads to rapid depopulation of the lowest excited singlet state via two competing mechanisms: proton transfer and enhanced internal conversion. The experimental results are rationalized by calculations which include specific and nonspecific solvent effects.
Źródło:
Acta Physica Polonica A; 2007, 112, S; S-105-S-120
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Network Properties of Ureasil-Based Polymer Matrixes for Construction of Amperometric Biosensors as Probed by PALS and Swelling Experiments
Autorzy:
Kavetskyy, T.
Šauša, O.
Čechová, K.
Švajdlenková, H.
Mat'ko, I.
Petkova, T.
Boev, V.
Ilcheva, V.
Smutok, O.
Kukhazh, Y.
Gonchar, M.
Powiązania:
https://bibliotekanauki.pl/articles/1033906.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Lg
81.07.Pr
78.70.Bj
61.25.hp
Opis:
Network properties of ureasil-based polymer matrixes suitable for construction of amperometric biosensors were probed by positron annihilation lifetime spectroscopy and swelling experiments. Temperature dependences of the ortho-positronium (o-Ps) lifetimes and their relative intensities were measured in a temperature range of 15-350 K. Glass transition temperatures and expansion coefficients of microscopical free-volume for the investigated polymers were determined. Differences in network behavior for the aged samples and the effect of chalcogenide (As₂S₃) particles on the free volume of ureasil network were observed. Swelling experiments using ethyl alcohol showed that the structure of the aged sample network had less swelling ability for the pure ureasil as well as composite. This suggests that the one of factors influencing swelling is the change of the basic ureasil network due to ageing. It is supposed that the network properties obtained by positron annihilation lifetime spectroscopy and swelling experiments could be very helpful to understand better the bio-functionality of the constructed biosensor based on the ureasil-chalcogenide glass composite.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1515-1518
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of pressure liquid extraction and ultrasonic irradiation frequency on inulin, phenolic content and antioxidant activity in burdock (Arctium lappa L.) roots
Autorzy:
Petkova, N.
Ivanov, I.
Mihaylova, D.
Lante, A.
Powiązania:
https://bibliotekanauki.pl/articles/12719126.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Przyrodniczy w Lublinie. Wydawnictwo Uniwersytetu Przyrodniczego w Lublinie
Opis:
Burdock (Arctium lappa L.) roots are traditionally used in folk medicine as diuretic and curing rheumatism, gastritis, gout, throat pain, arthritis and rashes. These pharmacological properties are due to many bioactive compounds such as flavonoids and fructooligosaccharides. Nowadays, the the application of “green” methods for extraction of natural compounds gains more and more attention. The object of the current research was to determine inulin and sugars content, phenolic content and antioxidant potential in 70% ethanol and water extracts obtained by two “green“ extraction methods, namely pressure-liquid extraction and ultrasound-assisted techniques. The content of total fructans, as well as inulin and sugars were analyzed by spectrophotometric resorcinol-thiourea method and high-performance liquid chromatography with refractive index detection. Total phenols and flavonoids were determined by Folin-Chiocalteu and Al(NO₃)₃ reagents. Antioxidant activity was evaluated by four reliable methods (DPPH, ABTS, FRAP and CUPRAC). The established inulin content varied from 0.27 to 4.0 g/100 g dw in prevalence of the ultrasound-assisted extract obtained with water. Additionally, the established phenolic compounds content (from 10.35 to 18.16 mg gallic acid equivalent (GAE)/g dw) and antioxidant activities demonstrated the burdock roots as potential source phytonutrients with health beneficial properties.
Źródło:
Acta Scientiarum Polonorum. Hortorum Cultus; 2020, 19, 3; 125-133
1644-0692
Pojawia się w:
Acta Scientiarum Polonorum. Hortorum Cultus
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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