3,061 research outputs found
Coherent Diffraction Imaging of Single 95nm Nanowires
Photonic or electronic confinement effects in nanostructures become
significant when one of their dimension is in the 5-300 nm range. Improving
their development requires the ability to study their structure - shape, strain
field, interdiffusion maps - using novel techniques. We have used coherent
diffraction imaging to record the 3-dimensionnal scattered intensity of single
silicon nanowires with a lateral size smaller than 100 nm. We show that this
intensity can be used to recover the hexagonal shape of the nanowire with a
28nm resolution. The article also discusses limits of the method in terms of
radiation damage.Comment: 5 pages, 5 figure
Loss of anti-tumour immunogenicity of a somatic cell hybrid line with increasing subculture.
Good immunoprotection was afforded by A9/SEWA somatic hybrid cells in the C3H mouse/C3H Py tumour system, confirming results previously obtained in the A.SW mouse/SEWA tumour system. However, in this study the immunogenicity decreased with increasing serial subculture of the hybrid line and concomitant chromosome loss
Some measurements of time and space correlation in wind tunnel
Results are presented of research obtained by means of an apparatus for measurement of time and space correlation and of a spectral analyzer in the study of the longitudinal component of turbulence velocities in a wind tunnel downstream of a grid of meshes. Application to the case of a flat-plate boundary layer is illustrated. These researches were made at the Laboratoire de Mecanique de l'Atmosphere de l'I.M.F.M. for the O.N.E.R.A
Apparatus for Measurements of Time and Space Correlation
A brief review is made of improvements to an experimental apparatus for time and space correlation designed for study of turbulence. Included is a description of the control of the measurements and a few particular applications
Nonresonant microwave absorption in epitaxial La-Sr-Mn-O films and its relation to colossal magnetoresistance
We study magnetic-field-dependent nonresonant microwave absorption and
dispersion in thin LaSrMnO films and show that it
originates from the colossal magnetoresistance. We develop the model for
magnetoresistance of a thin ferromagnetic film in oblique magnetic field. The
model accounts fairly well for our experimental findings, as well as for
results of other researchers. We demonstrate that nonresonant microwave
absorption is a powerful technique that allows contactless measurement of
magnetic properties of thin films, including magnetoresistance, anisotropy
field and coercive field.Comment: 20 pages, 11 figure
Dynamical structure of the inner 100 AU of the deeply embedded protostar IRAS 16293-2422
A fundamental question about the early evolution of low-mass protostars is
when circumstellar disks may form. High angular resolution observations of
molecular transitions in the (sub)millimeter wavelength windows make it
possible to investigate the kinematics of the gas around newly-formed stars,
for example to identify the presence of rotation and infall. IRAS 16293-2422
was observed with the extended Submillimeter Array (eSMA) resulting in
subarcsecond resolution (0.46" x 0.29", i.e. 55 35~AU) images
of compact emission from the CO (3-2) and CS (7-6) transitions at
337~GHz (0.89~mm). To recover the more extended emission we have combined the
eSMA data with SMA observations of the same molecules. The emission of
CO (3-2) and CS (7-6) both show a velocity gradient oriented
along a northeast-southwest direction with respect to the continuum marking the
location of one of the components of the binary, IRAS16293A. Our combined eSMA
and SMA observations show that the velocity field on the 50--400~AU scales is
consistent with a rotating structure. It cannot be explained by simple
Keplerian rotation around a single point mass but rather needs to take into
account the enclosed envelope mass at the radii where the observed lines are
excited. We suggest that IRAS 16293-2422 could be among the best candidates to
observe a pseudo-disk with future high angular resolution observations.Comment: Accepted for publication in ApJ, 18 pages, 10 figure
Herschel observations of EXtra-Ordinary Sources: Analysis of the HIFI 1.2 THz Wide Spectral Survey Toward Orion KL II. Chemical Implications
We present chemical implications arising from spectral models fit to the
Herschel/HIFI spectral survey toward the Orion Kleinmann-Low nebula (Orion KL).
We focus our discussion on the eight complex organics detected within the HIFI
survey utilizing a novel technique to identify those molecules emitting in the
hottest gas. In particular, we find the complex nitrogen bearing species
CHCN, CHCN, CHCN, and NHCHO systematically
trace hotter gas than the oxygen bearing organics CHOH, CHOH,
CHOCH, and CHOCHO, which do not contain nitrogen. If these
complex species form predominantly on grain surfaces, this may indicate
N-bearing organics are more difficult to remove from grain surfaces than
O-bearing species. Another possibility is that hot (T300 K)
gas phase chemistry naturally produces higher complex cyanide abundances while
suppressing the formation of O-bearing complex organics. We compare our derived
rotation temperatures and molecular abundances to chemical models, which
include gas-phase and grain surface pathways. Abundances for a majority of the
detected complex organics can be reproduced over timescales 10
years, with several species being under predicted by less than 3.
Derived rotation temperatures for most organics, furthermore, agree reasonably
well with the predicted temperatures at peak abundance. We also find that
sulfur bearing molecules which also contain oxygen (i.e. SO, SO, and OCS)
tend to probe the hottest gas toward Orion KL indicating the formation pathways
for these species are most efficient at high temperatures.Comment: 31 pages, 6 figures, 1 Table, accepted to the Astrophysical Journa
- …