720 research outputs found
Readers as research detectives
Flaws in research papers are common but it may require arduous detective work to unravel them. Checklists are helpful, but many inconsistencies will only be revealed through repeated cross-checks of every little detail, just like in a crime case. As a major deterrent for dishonesty, raw data from all trials should be posted on a public website. This would also make it much easier to detect errors and flaws in publications, and it would allow many research projects to be performed without collecting new data. The prevailing culture of secrecy and ownership to data is not in the best interests of patients
Nearly strain-free heteroepitaxial system for fundamental studies of pulsed laser deposition: EuTiO3 on SrTiO3
High quality epitaxial thin-films of EuTiO3 have been grown on the (001)
surface of SrTiO3 using pulsed laser deposition. In situ x-ray reflectivity
measurements reveal that the growth is two-dimensional and enable real-time
monitoring of the film thickness and roughness during growth. The film
thickness, surface mosaic, surface roughness, and strain were characterized in
detail using ex situ x-ray diffraction. The thicnkess and composition were
confirmed with Rutherford Backscattering. The EuTiO3 films grow
two-dimensionally, epitaxially, pseudomorphically, with no measurable in-plane
lattice mismatch.Comment: 7 pages, 6 figure
Capillary Filling of Anodized Alumina Nanopore Arrays
The filling behavior of a room temperature solvent,
perfluoromethylcyclohexane, in approximately 20 nm nanoporous alumina membranes
was investigated in situ with small angle x-ray scattering. Adsorption in the
pores was controlled reversibly by varying the chemical potential between the
sample and a liquid reservoir via a thermal offset, T. The system
exhibited a pronounced hysteretic capillary filling transition as liquid was
condensed into the nanopores. These results are compared with Kelvin-Cohan
theory, with a modified Derjaguin approximation, as well as with predictions by
Cole and Saam.Comment: 4 pages, 3 figures, pre-proof
Induced Crystallization of Polyelectrolyte-Surfactant Complexes at the Gas-Water Interface
Synchrotron-X-ray and surface tension studies of a strong polyelectrolyte
(PE) in the semi-dilute regime (~ 0.1M monomer-charges) with varying surfactant
concentrations show that minute surfactant concentrations induce the formation
of a PE-surfactant complex at the gas/solution interface. X-ray reflectivity
and grazing angle X-ray diffraction (GIXD) provide detailed information of the
top most layer, where it is found that the surfactant forms a two-dimensional
liquid-like monolayer, with a noticeable disruption of the structure of water
at the interface. With the addition of salt (NaCl) columnar-crystals with
distorted-hexagonal symmetry are formed.Comment: 4 pages, 5 eps figure
Numerical study of surface-induced reorientation and smectic layering in a nematic liquid crystal
Surface-induced profiles of both nematic and smectic order parameters in a
nematic liquid crystal, ranging from an orienting substrate to "infinity", were
evaluated numerically on base of an extended Landau theory. In order to obtain
a smooth behavior of the solutions at "infinity" a boundary energy functional
was derived by linearizing the Landau energy around its equilibrium solutions.
We find that the intrinsic wave number of the smectic structure, which plays
the role of a coupling between nematic and smectic order, strongly influences
the director reorientation. Whereas the smectic order is rapidly decaying when
moving away from the surface, the uniaxial nematic order parameter shows an
oscillatory behavior close to the substrate, accompanied by a non-zero local
biaxiality.Comment: LaTeX, 17 pages, with 4 postscript figure
Microscopic calculation of the spin-dependent neutron scattering lengths on 3He
We report on the spin.dependent neutron scattering length on 3He from a
microscopic calculation of p-3H, n-3He, and d-2H scattering employing the
Argonne v18 nucleon-nucleon potential with and without additional three-nucleon
force. The results and that of a comprehensive R-matrix analysis are compared
to a recent measurement. The overall agreement for the scattering lengths is
quite good. The imaginary parts of the scattering lengths are very sensitive to
the inclusion of three-nucleon forces, whereas the real parts are almost
insensitive.Comment: 9 pages, 1 figur
On electromagnetic contributions in WIMP quests
The effect pointed out by A. B. Migdal in the 40's (hereafter named Migdal
effect) has so far been usually neglected in the direct searches for WIMP Dark
Matter candidates. This effect consists in the ionization and the excitation of
bound atomic electrons induced by the recoiling atomic nucleus. In the present
paper the related theoretical arguments are developed and some consequences of
the proper accounting for this effect are discussed by some examples of
practical interest.Comment: 14 pages, 6 figures, 2 tables, Int. J. Mod. Phys. A (in publication
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