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Self-diffusion effects in micro scale liquids. Numerical study by a dissipative particle dynamics method

100%

Czerwińska J.

tom Vol. 55, nr 2

159-171

Mesoscale flows of liquid are of great importance for various nano- and biotechnology applications. Continuum model do not properly capture the physical phenomena related to the diffusion effects, such as Brownian motion. Molecular approach on the other band, is computationally too expensive to provide information relevant for engineering applications. Hence, the need for a mesoscale approach is apparent. In recent years many mesoscale models have been developed, particularly to study flows of gas. However, mesoscale behaviour of liquid substantially differs tram that of gas. This paper presents a numerical study of micro-liquids phenomena by a Voronoi Dissipative Particle Dynamics method. The method bas its origin tram the material science field and is one of very few numerical techniques which ran describe correctly molecular diffusion processes in mesoscale liquids. This paper proves that correct prediction of molecular diffusion effects plays predominant role on the correct prediction of behaviour of immersed structures in the mesoscopic flow.

Implementation of velocity slip and temperature jump boundary conditions for microfluidic devices

63%

Jebauer S. , Czerwińska J.

Prace Instytutu Podstawowych Problemów Techniki PAN

2007

tom nr 5

1-50

The motivation of this work is to obtain a simulation tool which will be capable of modelling simple micro-devices in the gas slip flow regime. To achieve this goal Maxwell Smoluchowski boundary conditions were implemented by means of a udf routine into the commercial fluid finite volume solver Fluent. The applied velocity slip and temperature jump boundary condition are varied for small Knudsen numbers Kn < 0.1. In this regime there are several industrial applications such as micro-electro-mechanical systems (MEMS), heat exchange on chips and boundary layer problems for aerospace and turbomachinery applications. This report shows how the boundary condition implementation was done and is applied to a number of test cases: flow through a rectangular channel, Couette flow between two cylindrical surfaces, thermal creep flowr between two heated tanks, flowr through a bended diverging channel, a box heated with different wall temperatures and a vortex pattern flow between cylindrical surfaces heated with different temperatures.

Treatment with silver nanoparticles delays repair of X-ray induced DNA damage in HepG2 cells

32%

Wojewódzka M. , Lankoff A. , Dusińska M. , Brunborg G. , Czerwińska J. , Iwaneńko T. , Stępkowski T. , Szumiel I. , Kruszewski M.

tom Vol. 56, No. 1

29-33

Nanoparticles (NPs) defined as particles having at least one dimension below 100 nm have been applied in the last decade in industry and medicine. Recently, there is an increased concern about the biohazard aspect of the presence of NP in consumer goods and in the environment. Silver NP (Ag NP) cause oxidative stress in mammalian cells in result of generation of reactive oxygen species (ROS). This results in genotoxicity and mutagenicity, disturbed mitochondrial respiration, slowed proliferation and cell death. Using the alkaline comet assay, we examined the effect of combined treatment with Ag NP 20 nm or 200 nm and X-rays (2 Gy) in HepG2 cells. In addition, combined treatment with X-rays and titanium dioxide NP (TiO2 NP) 21 nm was also studied. No effect of NP pre-treatment on X-ray induced initial deoxyribonucleic acid (DNA) damage levels was observed for all three NP. In contrast, Ag NP treatment preceding exposure to X-rays caused a marked decrease in the rate of single strand break rejoining. The effect was particularly strong for Ag NP 20 nm. TiO2 NP pre-treatment had no effect on DNA repair.