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  • Author or Editor: V. Živanović x
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Abstract  

The crystallization of K2O·TiO2·3GeO2 glass under non-isothermal condition was studied. In powdered glass with particle sizes less than 0.15 mm, surface crystallization was dominant and an activation energy of crystal growth of E a,s=327±50 kJ mol−1 was calculated. In the size range 0.15 to 0.45 mm, both surface and volume crystallization occurred. For particle sizes >0.45 mm, volume crystallization dominated with spherulitic morphology of the crystals growth and E a,v=359±64 kJ mol−1 was calculated.

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Abstract  

The effect of replacing 20 mol% of GeO2 by TiO2 on the properties of potassium germanate glass was investigated. The structure and devitrification behaviour of glasses were studied by Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and X-ray diffraction (XRD). It was observed that potassium titanium germanate has a higher glass transition temperature and a higher thermal stability vs. crystallization. The presence of two exothermic peaks on the DTA curve of potassium germanate glass indicates the complex crystallization process. The XRD pattern of this glass heated at the temperature of the first crystallization peak indicated that the GeO2 and K2Ge7O15 were formed. Only the K2TiGe3O9 phase was identified, in a case when potassium titanium germanate glass was heated at the temperature of the crystallization peak.

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Acta Physiologica Hungarica
Authors:
Vladimir Ajdžanović
,
V Jakovljević
,
D Milenković
,
A Konić-Ristić
,
J Živanović
,
I Jarić
, and
V Milošević

Purpose: Deformability/rheologic behavior of erythrocytes are related to near-surface membrane fluidity. Specific agents can increase erythrocyte membrane fluidity in order to adjust hemodynamics in cardiovascular diseases. Grapefruit flavanone naringenin has been proposed for potential use in an alternative therapy of cardiovascular conditions. In respect to this, we assessed here effects of two nutritionally relevant concentrations of naringenin (0.1 and 1 μg/ml) on near-surface membrane fluidity in human erythrocytes. Methods: We used electron paramagnetic resonance spectroscopy and fatty acid spin probes (5-DS and 7-DS), the spectra of which are dependent on membrane fluidity. Results: The results showed a significant (p = 0.029) increase of membrane fluidity near the hydrophilic surface in erythrocytes treated with higher concentration of naringenin. In the deeper layer, just below the erythrocyte membrane phospholipid heads, both lower and higher concentration of naringenin significantly increased membrane fluidity (p = 0.036 and p = 0.028, respectively). Conclusions: These data document the positive and dose dependent effect of naringenin on near-surface membrane fluidity in human erythrocytes, recommending its use in the cardiovascular conditions characterized by disturbed hemodynamics.

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