On continuum modeling of sputter erosion under normal incidence: interplay between nonlocality and nonlinearity

Under specific experimental circumstances, sputter erosion on semiconductor materials exhibits highly ordered hexagonal dot-like nanostructures. In a recent attempt to theoretically understand this pattern forming process, Facsko et al. [Phys. Rev. B 69, 153412 (2004)] suggested a nonlocal, damped Kuramoto-Sivashinsky equation as a potential candidate for an adequate continuum model of this self-organizing process. In this study we theoretically investigate this proposal by (i) formally deriving such a nonlocal equation as minimal model from balance considerations, (ii) showing that it can be exactly mapped to a local, damped Kuramoto-Sivashinsky equation, and (iii) inspecting the consequences of the resulting non-stationary erosion dynamics.Comment: 7 pages, 2 Postscript figures, accepted by Phys. Rev. B corrected typos, few minor change

Synthesis, Self-Assembly and In Vitro Cellular Uptake Kinetics of Nanosized Drug Carriers Based on Aggregates of Amphiphilic Oligomers of N-Vinyl-2-pyrrolidone

Development of nanocarrier-based drug delivery systems is a major breakthrough in pharmacology, promising targeted delivery and reduction in drug toxicity. On the cellular level, encapsulation of a drug substantially affects the endocytic processes due to nanocarrier–membrane interaction. In this study we synthesized and characterized nanocarriers assembled from amphiphilic oligomers of N-vinyl-2-pyrrolidone with a terminal thiooctadecyl group (PVP-OD). It was found that the dissolution free energy of PVP-OD depends linearly on the molecular mass of its hydrophilic part up to [Formula: see text] = 2 × 10(4), leading to an exponential dependence of critical aggregation concentration (CAC) on the molar mass. A model hydrophobic compound (DiI dye) was loaded into the nanocarriers and exhibited slow release into the aqueous phase on a scale of 18 h. Cellular uptake of the loaded nanocarriers and that of free DiI were compared in vitro using glioblastoma (U87) and fibroblast (CRL2429) cells. While the uptake of both DiI/PVP-OD nanocarriers and free DiI was inhibited by dynasore, indicating a dynamin-dependent endocytic pathway as a major mechanism, a decrease in the uptake rate of free DiI was observed in the presence of wortmannin. This suggests that while macropinocytosis plays a role in the uptake of low-molecular components, this pathway might be circumvented by incorporation of DiI into nanocarriers

Large Scale Structures a Gradient Lines: the case of the Trkal Flow

A specific asymptotic expansion at large Reynolds numbers (R)for the long wavelength perturbation of a non stationary anisotropic helical solution of the force less Navier-Stokes equations (Trkal solutions) is effectively constructed of the Beltrami type terms through multi scaling analysis. The asymptotic procedure is proved to be valid for one specific value of the scaling parameter,namely for the square root of the Reynolds number (R).As a result large scale structures arise as gradient lines of the energy determined by the initial conditions for two anisotropic Beltrami flows of the same helicity.The same intitial conditions determine the boundaries of the vortex-velocity tubes, containing both streamlines and vortex linesComment: 27 pages, 2 figure

Получение диагностических тест-систем на основе полимерных микросфер в присутствии поливинилпирролидона, модифицированного аминокислотой

Styrene-divinylbenzene particles (6 microns in diameter) with carboxyl groups on the surface have been synthesized by seed polymerization in the presence of an organosilicon carboxyl-containing surfactant soluble in the monomer phase. It has been shown that carboxyl groups on the microsphere surface are accessible for covalent immobilization of bioligands and alanine-modified polyvinylpyrrolidone. It was supposed that applying modified polyvinylpyrrolidone for obtaining diagnostic systems based on polymer microspheres is very perspective.етодом затравочной полимеризации в присутствии растворимого в мономерной фазе кремнийорганического карбоксилсодержащего ПАВ были синтезированы сополимерные стирол-дивинилбензольные микросферы диаметром 6 мкм с карбоксильными группами на поверхности. Было показано, что карбоксильные группы доступны для ковалентного связывания биолигандов и поливинилпирролидона, модифицированного аланином. Высказано предположение о перспективности применения поливинилпирролидона, модифицированного аланином, для получения диагностических систем на основе полимерных микросфер

Negative viscosity effect in three-dimensional flows

The paper treats the stability of a periodic unidirectional three-dimensional flow. It is shown that at sufficiently high Reynolds numbers a flow of this type is unstable to long-wave disturbances. This instability can be interpreted in terms of negative effective viscosity of the corresponding large-scale flow.On étudie la stabilité d'un écoulement tridimensionnel, unidirectionnel, périodique. On montre qu'à nombre de Reynolds suffisamment grand, un écoulement de ce type est instable vis-à-vis de perturbations de grande longueur d'onde. Cette instabilité peut être interprétée en termes de viscosité effective négative pour l'écoulement à grande échelle correspondant