364 research outputs found
First-principles calculations for the adsorption of water molecules on the Cu(100) surface
First-principles density-functional theory and supercell models are employed
to calculate the adsorption of water molecules on the Cu(100) surface. In
agreement with the experimental observations, the calculations show that a H2O
molecule prefers to bond at a one-fold on-top (T1) surface site with a tilted
geometry. At low temperatures, rotational diffusion of the molecular axis of
the water molecules around the surface normal is predicted to occur at much
higher rates than lateral diffusion of the molecules. In addition, the
calculated binding energy of an adsorbed water molecule on the surfaces is
significantly smaller than the water sublimation energy, indicating a tendency
for the formation of water clusters on the Cu(100) surface.Comment: 5 pages, 3 figures, submitted to Phys. Rev.
A study of random resistor-capacitor-diode networks to assess the electromagnetic properties of carbon nanotube filled polymers
We determined the frequency dependent effective permittivity of a large
ternary network of randomly positioned resistors, capacitors, and diodes. A
linear circuit analysis of such systems is shown to match the experimental
dielectric response of single-walled carbon nanotube (SWCNT) filled polymers.
This modeling method is able to reproduce the two most important features of
SWCNT filled composites, i.e. the low frequency dispersion and dipolar
relaxation. As a result of the modeling important physical conclusion proved by
the experimental data was done: the low frequency behavior of SWCNT-filled
polymer composites is mostly caused by the fraction of semiconducting SWCNTs
Measurement of the microwave effective permittivity in tensile-strained polyvinylidene difluoride trifluoroethylene filled with graphene
We report an interesting effect in the form of a rise (up to 13%) in the permittivity of graphene (GE) filled polyvinylidene difluoride trifluoroethylene (P(VDF-TrFE)) subjected to a small uniaxial deformation (up to 7% in the principal direction). Our findings differ from GE-PVDF homopolymer samples that show a decrease of permittivity upon elongation. We argue that the VDF content which controls the spontaneous polarization has a profound effect on the charge storage through the addition of interface density by the GE phase. (C) 2014 AIP Publishing LLC
Synthesis and characterization of core-shell structure silica-coated Fe29.5Ni70.5 nanoparticles
In view of potential applications of magnetic particles in biomedicine and
electromagnetic devices, we made use of the classical Stober method
base-catalysed hydrolysis and condensation of tetraethoxysilane (TEOS) to
encapsulate FeNi nanoparticles within a silica shell. An original stirring
system under high power ultrasounds made possible to disperse the otherwise
agglomerated particles. Sonication guaranteed particles to remain dispersed
during the Stober synthesis and also improved the efficiency of the method. The
coated particles are characterized by electron microscopy (TEM) and
spectroscopy (EDX) showing a core-shell structure with a uniform layer of
silica. Silica-coating does not affect the core magnetic properties. Indeed,
all samples are ferromagnetic at 77 K and room temperature and the Curie point
remains unchanged. Only the coercive force shows an unexpected non-monotonous
dependence on silica layer thickness.Comment: Regular paper submited to international peer-reveiwed journa
Quantum light depolarization: the phase-space perspective
Quantum light depolarization is handled through a master equation obtained by
coupling dispersively the field to a randomly distributed atomic reservoir.
This master equation is solved by transforming it into a quasiprobability
distribution in phase space and the quasiclassical limit is investigated.Comment: 6 pages, no figures. Submitted for publicatio
Preclinical evaluation of porcine colon resection using hollow core negative curvature fibre delivered ultrafast laser pulses
Microwave and mechanical properties of quartz/graphene-based polymer nanocomposites
We report microwave spectroscopy studies of graphene-based polymer-matrix composite materials subject to uniaxial elongation. The samples were prepared via shear mixing under the same thermal processing conditions of amorphous styrene butadiene rubber (SBR) with quartz grains on the order of micrometers in size and/or graphene sheets with thickness 10-20 nm and average lateral size 200 mu m. An important result is the observation of a significant increase (up to 25%) in the effective microwave permittivity of hybridized nanocomposites comprising both quartz and graphene compared to the nanocomposites with quartz only. We suggest that the coating of quartz grains by graphene sheets is the most likely origin of this synergetic effect. In all cases, we also observe that the permittivity spectrum is unaffected by strain up to 8%. By examining the mechanical response, it is shown that the elasticity network of SBR polymer chains is significantly affected in the rubbery state by filling SBR with graphene and quartz particles. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793411
Quantum polarization tomography of bright squeezed light
We reconstruct the polarization sector of a bright polarization squeezed beam
starting from a complete set of Stokes measurements. Given the symmetry that
underlies the polarization structure of quantum fields, we use the unique SU(2)
Wigner distribution to represent states. In the limit of localized and bright
states, the Wigner function can be approximated by an inverse three-dimensional
Radon transform. We compare this direct reconstruction with the results of a
maximum likelihood estimation, finding an excellent agreement.Comment: 15 pages, 5 figures. Contribution to New Journal of Physics, Focus
Issue on Quantum Tomography. Comments welcom
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