25 research outputs found
Magnetoresistance and surface roughness study of the initial growth of electrodeposited Co/Cu multilayers
The giant magnetoresistance (GMR) effect has been widely investigated on electrodeposited ferromagnetic/non-magnetic (FM/NM) multilayers generally containing a large number of bilayers. In most applications of the GMR effect, layered structures consisting of a relatively small number of consecutive FM and NM layers are used. It is of great interest, therefore, to investigate the initial stages of GMR multilayer film growth by electrodeposition. In the present work we have extended our previous studies on ED GMR multilayers to layered structures with a total thickness ranging from a few nanometers up to 70 nm. The evolution of the surface roughness and electrical transport properties of such ultrathin ED Co/Cu layered structures was investigated. Various layer combinations were produced including both Co and Cu either as starting or top layers in order (i) to see differences in the nucleation of the first layer and (ii) to trace out the effect of the so called exchange reaction. Special attention was paid to measure the field dependence of the magnetoresistance, MR(H) in order to derive information for the appearance of superparamagnetic regions in the magnetic layers. This proved to be helpful for monitoring the evolution of the layer microstructure at each step of the deposition sequence
Suspension of Water Droplets on Individual Pillars
We report results of extensive experimental and numerical studies on the suspension of water drops deposited on cylindrical pillars having circular and square cross sections and different wettabilities. In the case of circular pillars, the drop contact line is pinned to the whole edge contour until the drop collapses due to the action of gravity. In contrast, on square pillars, the drops are suspended on the four corners and spilling along the vertical walls is observed. We have also studied the ability of the two geometries to sustain drops and found that if we compare pillars with the same characteristic size, the square is more efficient in pinning large volumes, while if we normalize the volumes to pillar areas, the opposite is true
The Effect of Newly Developed OPLS-AA Alanyl Radical Parameters on Peptide Secondary Structure
Recent studies using ab initio calculations have shown
that C<sub>Ī±</sub>-centered radical formation by H-abstraction
from the
backbone of peptide residues has dramatic effects on peptide structure
and have suggested that this reaction may contribute to the protein
misfolding observed in Alzheimerās and Parkinsonās diseases.
To enable the effects of C<sub>Ī±</sub>-centered radicals to
be studied in longer peptides and proteins over longer time intervals,
force-field parameters for the C<sub>Ī±</sub>-centered Ala radical
were developed for use with the OPLS force field by minimizing the
sum of squares deviation between the quantum chemical and OPLS-AA
energy hypersurfaces. These parameters were used to determine the
effect of the C<sub>Ī±</sub>-centered Ala radical on the structure
of a hepta-alanyl peptide in molecular dynamics (MD) simulations.
A negligible sum-of-squares energy deviation was observed in the stretching
parameters, and the newly developed OPLS-AA torsional parameters showed
a good agreement with the LMP2/cc-pVTZĀ(-f) hypersurface. The parametrization
also demonstrated that derived force-field bond length and bond angle
parameters can deviate from the quantum chemical equilibrium values,
and that the improper torsional parameters should be developed explicitly
with respect to the coupled torsional parameters. The MD simulations
showed planar conformations of the C<sub>Ī±</sub>-containing
residue (Alr) are preferred and these conformations increase the formation
of Ī³-, Ī±-, and Ļ-turn structures depending on the
position in the turn occupied by the Alr residue. Higher-ordered structures
are destabilized by Alr except when this residue occupies position
āi + 1ā of the 3<sub>10</sub>-helix. These results offer
new insight into the protein-misfolding mechanisms initiated by H-abstraction
from the C<sub>Ī±</sub> of peptide and protein residues
Structure of sputtered nanocomposite CrC[sub x]āa-C:H thin films
This work presents the structural evolution of nanocomposite CrCxāa-C:H coatings prepared by unbalanced magnetron sputtering of a metallic Cr target in Ar+CH4 glow discharges using low negative dc bias voltages. Raman spectroscopy and x-ray photoelectron spectroscopy were used to characterize the phase composition and the chemical bonding in the films deposited at different experimental conditions. The results were correlated to the chemical composition obtained by elastic recoil detection analysis. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy combined with electron energy-loss spectroscopy analysis. The nanocomposite coatings can be divided into hard CrCx dominated films, when prepared at low CH4 partial pressure to total pressure (pt) ratios (pCH4/pt0.4. The structure of the low-friction a-C:H dominated coatings consists of 2ā10nm sized fcc CrC crystallites embedded in a Cr containing a-C:H matrix