Self-assembling chitosan/poly-γ-glutamic acid nanoparticles for targeted drug delivery

For the purpose of targeted drug delivery, composite biodegradable nanoparticles were prepared from chitosan and the poly-γ-glutamic acid via an ionotropic gelation process. These stable self-assembled nanoparticles were characterized by dynamic light scattering, transmission electron microscopy, and atomic force microscopy, which demonstrated that the nanosystem consists of spherical particles with a smooth surface both in aqueous environment and in dried state. Toxicity measurements showed that the composition is nontoxic when tested either on cell cultures or in animal feeding experiments. To evaluate the potential of the nanosystem for intracellular drug delivery, the nanoparticles were fluorescently labeled and folic acid was attached as a cancer cell-specific targeting moiety. The ability of the particles to be internalized was tested using confocal microscopic imaging on cultured A2780/AD ovarian cancer cells, which overexpress folate receptors. The quantitative data obtained by digital processing of the intensity of green color of each pixel in the pictures inside the cell boundaries and total intensity of fluorescence inside the cells showed that “targeted” particles internalized into the cells significantly faster and the total accumulation of these particles was substantially higher in the cancer cells when compared with “nontargeted” particles, which may facilitate effective and specific cytoplasmic delivery of anticancer agents loaded into such nanoparticles. Zsolt Keresztessy and Magdolna Bodnár contributed equally to this work.     

Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.     

On the quantum limit behaviour of the magnetoresistance in non-parabolic semiconductors

The quantum limit behaviour of the magnetoresistance in narrow-gap semiconductors is investigated. The non-parabolicity of the energy dispersion is taken into account in the density of states. Assuming constant level broadening, both the longitudinal and the transverse magnetoresistance obey asymptotic power laws. The exponents in these power laws are found to be larger than in the case of parabolic energy dispersion.     

On the Diophantine Equations (2 n − 1)(6 n − 1) = x 2 and (a n − 1)(a kn − 1) = x 2

In this paper we prove that the equation (2 ⁿ – 1)(6 ⁿ – 1) = x ² has no solutions in positive integers n and x. Furthermore, the equation (a ⁿ – 1) (a ^kn – 1) = x ² in positive integers a > 1, n, k > 1 (kn > 2) and x is also considered. We show that this equation has the only solutions (a,n,k,x) = (2,3,2,21), (3,1,5,22) and (7,1,4,120).