Biomedical subjects

N Stefanou

Publications and source records attributed to N Stefanou.

17 recordsLinked to original sources

PubMed2007

Hypersonic acoustic excitations in binary colloidal crystals: big versus small hard sphere control.

The phononic band structure of two binary colloidal crystals, at hypersonic frequencies, is studied by means of Brillouin light scattering and analyzed in conjunction with corresponding dispersion diagrams of the single colloidal crystals of the constituent particles. Besides the acoustic band of the average medium, the authors' results show the existence of narrow bands originating from resonant multipole modes of the individual particles as well as Bragg-type modes due to the (short-range) periodicity. Strong interaction, leading to the occurrence of hybridization gaps, is observed between the acoustic band and the band of quadrupole modes of the particles that occupy the largest fractional volume of the mixed crystal; the effective radius is either that of the large (in the symmetric NaCl-type crystalline phase) or the small (in the asymmetric NaZn(13)-type crystalline phase) particles. The possibility to reveal a universal behavior of the phononic band structure for different single and binary colloidal crystalline suspensions, by representing in the dispersion diagrams reduced quantities using an appropriate length scale, is discussed.

Journal Article↗

PubMed2005

Widening of phononic transmission gaps via Anderson localization.

We demonstrate the existence of strong Anderson localization in certain disordered phononic systems. As a result, the transmission coefficient of elastic waves through a slab of the material practically vanishes, whatever the angle of incidence, over a region of frequency much wider than the absolute frequency gap of the corresponding ordered system. The phenomenon can be of use in the design of phononic systems with very wide absolute transmission gaps.

Journal Article↗

PubMed2002

Experimental hyperlipidemia and the effect of NSAIDs.

The effects of ip administration of NSAIDs in experimentally induced hyperlipidemia in rats was studied. An isotonic solution of Triton WR1339 (tyloxapol) was administered ip to rats one hour after ip administration of the examined anti-inflammatory drug. After 24 h, blood was collected for the determination of plasma total cholesterol (TC), LDL and trigluceride (TG) concentrations. The NSAIDs used in our experimental model are selective or non selective COX-1 inhibitors as well as one non selective COX-2 inhibitor. Most of the drugs significantly reduced the TC, TG and LDL concentrations in the plasma of hyperlipidemic rats. While studies link atheromatosis to inflammation, our results potentially also link anti-inflammatory activity with hypolipidemia. Thus, NSAIDs not only may address the inflammatory aspect of atherosclerosis but also may contribute directly by inducing hypolipidemia.

Animals↗

PubMed2001

Effect of stacking faults on the optical properties of inverted opals.

Stacking faults appear to be the most common type of defect in inverted opals which are good candidates for photonic crystals with absolute gaps in the visible range of light. In this Letter we present for the first time a systematic study of the effect of stacking faults on the optical properties of self-assembled photonic crystals, by means of large-scale transmittance calculations for macroscopic slabs of inverted opals with randomly distributed stacking faults. We show that frequency gaps, as seen in optical transmission experiments, will in general appear wider in the presence of stacking faults. We attribute the above to Anderson localization of light due to disorder.

Journal Article↗

PubMed1996