66 research outputs found
Study on physio-chemical properties of plasma polymerization in C2H2/N2 plasma and their impact on COL X
Nitrogen-containing plasma polymerization is of considerable interest for tissue engineering due
to their properties on cell adhesion and mesenchymal stem cells (MSCs) response. In this study,
low-pressure RF plasma of acetylene and nitrogen was used to deposit nitrogen-containing plasma
polymerized coatings on several substrates. Deposition kinetics and surface characteristics of coatings
were investigated in terms of RF power and gas flow ratio. OES was used to monitor the plasma process
and investigate the relation between the film structure and plasma species. Presence of several bonds
and low concentration of amine functional groups were determined using FTIR and Colorimetric
methods. Contact angle goniometry results indicated about 30% increase in surface hydrophilicity.
Stability of coatings in air and two different liquid environments was examined by repeating surface
free energy measurements. Deposited films exhibited acceptable stability during the storage duration.
Surface roughness measured by AFM was found to decrease with growing concentration of nitrogen.
The deposition rate increased with increasing RF power and decreased with growing concentration of
nitrogen. Zeta potential measurements of coatings revealed the negative potential on the surface of
the thin films. Temporary suppression of collagen X in the presence of plasma coatings was confirmed
by RT-PCR results
Precise Calculation of Single and Double Ionization of Hydrogen Molecule in Intense Laser Pulses
A new simulation box setup is introduced for the precise description of the
wavepacket evolution of two electronic systems in intense laser pulses. In this
box, the regions of the hydrogen molecule H, and singly and doubly
ionized species, H and H, are well recognized and their
time-dependent populations are calculated at different laser field intensities.
In addition, some new regions are introduced and characterized as quasi-double
ionization and their time-dependencies on the laser field intensity are
calculated and analyzed. The adopted simulation box setup is special in that it
assures proper evaluation of the second ionization. In this study, the dynamics
of the electrons and nuclei of the hydrogen molecule are separated based on the
adiabatic approximation. The time-dependent Schr\"{o}dinger and Newton
equations are solved simultaneously for the electrons and the nuclei,
respectively. Laser pulses of 390 nm wavelength at four different intensities
(i.e. , , , and W cm) are used in these simulations. Details of the
central H region is also presented and discussed. This region is divided
into four sub-regions related to the ionic state HH and covalent
(natural) state HH. The effect of the motion of nuclei on the enhanced
ionization is discussed. Finally, some different time-dependent properties are
calculated and their dependencies on the intensity of the laser pulse are
studied, and their correlations with the populations of different regions are
analyzed.Comment: 30 pages, 17 figure
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