2,365 research outputs found
Archeops: an instrument for present and future cosmology
Archeops is a balloon-borne instrument dedicated to measure the cosmic
microwave background (CMB) temperature anisotropies. It has, in the millimetre
domain (from 143 to 545 GHz), a high angular resolution (about 10 arcminutes)
in order to constrain high l multipoles, as well as a large sky coverage
fraction (30%) in order to minimize the cosmic variance. It has linked, before
WMAP, Cobe large angular scales to the first acoustic peak region. From its
results, inflation motivated cosmologies are reinforced with a flat Universe
(Omega_tot=1 within 3%). The dark energy density and the baryonic density are
in very good agreement with other independent estimations based on supernovae
measurements and big bang nucleosynthesis. Important results on galactic dust
emission polarization and their implications for Planck are also addressed.Comment: 4 pages, 2 figures, to appear in Proceedings of the Multiwavelength
Cosmology Conference, June 2003, Mykonos Island, Greec
Submillimetre point sources from the Archeops experiment: Very Cold Clumps in the Galactic Plane
Archeops is a balloon-borne experiment, mainly designed to measure the Cosmic
Microwave Background (CMB) temperature anisotropies at high angular resolution
(~ 12 arcminutes). By-products of the mission are shallow sensitivity maps over
a large fraction of the sky (about 30 %) in the millimetre and submillimetre
range at 143, 217, 353 and 545 GHz. From these maps, we produce a catalog of
bright submillimetre point sources. We present in this paper the processing and
analysis of the Archeops point sources. Redundancy across detectors is the key
factor allowing to sort out glitches from genuine point sources in the 20
independent maps. We look at the properties of the most reliable point sources,
totalling 304. Fluxes range from 1 to 10,000 Jy (at the frequencies covering
143 to 545 GHz). All sources are either planets (2) or of galactic origin.
Longitude range is from 75 to 198 degrees. Some of the sources are associated
with well-known Lynds Nebulae and HII compact regions in the galactic plane. A
large fraction of the sources have an IRAS counterpart. Except for Jupiter,
Saturn, the Crab and Cas A, all sources show a dust-emission-like modified
blackbody emission spectrum. Temperatures cover a range from 7 to 27 K. For the
coldest sources (T<10 K), a steep nu^beta emissivity law is found with a
surprising beta ~ 3 to 4. An inverse relationship between T and beta is
observed. The number density of sources at 353 GHz with flux brighter than 100
Jy is of the order of 1 per degree of Galactic longitude. These sources will
provide a strong check for the calibration of the Planck HFI focal plane
geometry as a complement to planets. These very cold sources observed by
Archeops should be prime targets for mapping observations by the Akari and
Herschel space missions and ground--based observatories.Comment: Version matching the published article (English improved). Published
in Astron. Astrophys, 21 pages, 13 figures, 4 tables Full article (with
complete tables) can be retrieved at
http://www.archeops.org/Archeops_Publicatio
Effects of Nuclear Structure on Quasi-fission
The quasi-fission mechanism hinders fusion of heavy systems because of a mass
flow between the reactants, leading to a re-separation of more symmetric
fragments in the exit channel. A good understanding of the competition between
fusion and quasi-fission mechanisms is expected to be of great help to optimize
the formation and study of heavy and superheavy nuclei. Quantum microscopic
models, such as the time-dependent Hartree-Fock approach, allow for a treatment
of all degrees of freedom associated to the dynamics of each nucleon. This
provides a description of the complex reaction mechanisms, such as
quasi-fission, with no parameter adjusted on reaction mechanisms. In
particular, the role of the deformation and orientation of a heavy target, as
well as the entrance channel magicity and isospin are investigated with
theoretical and experimental approaches.Comment: Invited talk to NSRT12. To be published in Eur. Phys. J. Web of Con
An update on Archeops: flights and data products
Archeops is a balloon-borne instrument dedicated to measuring CMB temperature
anisotropies at high resolution over a large fraction of sky. We present the
Archeops flights and data products, Archeops results, and the future use of
Archeops data for multi-experiment data analysis
Slippage of water past superhydrophobic carbon nanotube forests in microchannels
We present in this letter an experimental characterization of liquid flow
slippage over superhydrophobic surfaces made of carbon nanotube forests,
incorporated in microchannels. We make use of a micro-PIV (Particule Image
Velocimetry) technique to achieve the submicrometric resolution on the flow
profile necessary for accurate measurement of the surface hydrodynamic
properties. We demonstrate boundary slippage on the Cassie superhydrophobic
state, associated with slip lengths of a few microns, while a vanishing slip
length is found in the Wenzel state, when the liquid impregnates the surface.
Varying the lateral roughness scale L of our carbon nanotube forest-based
superhydrophobic surfaces, we demonstrate that the slip length varies linearly
with L in line with theoretical predictions for slippage on patterned surfaces.Comment: under revie
Excitability in ramped systems: the compost-bomb instability
Copyright © 2010 The Royal SocietyOpen Access articleThe paper studies a novel excitability type where a large excitable response appears when a system’s parameter is varied gradually, or ramped, above some critical rate. This occurs even though there is a (unique) stable quiescent state for any fixed setting of the ramped parameter. We give a necessary and a sufficient condition for the existence of a critical ramping rate in a general class of slow–fast systems with folded slow (critical) manifold. Additionally, we derive an analytical condition for the critical rate by relating the excitability threshold to a canard trajectory through a folded saddle singularity. The general framework is used to explain a potential climate tipping point termed the ‘compost-bomb instability’—an explosive release of soil carbon from peatlands into the atmosphere occurs above some critical rate of global warming even though there is a unique asymptotically stable soil carbon equilibrium for any fixed atmospheric temperature
Sensitivity to the initial state of interacting ultracold bosons in disordered lattices
We study the dynamics of a nonlinear one-dimensional disordered system
obtained by coupling the Anderson model with the Gross-Pitaevskii equation. An
analytical model provides us with a single quantity globally characterizing the
localization of the system. This quantity obeys a scaling law with respect to
the width of the initial state, which can be used to characterize the dynamics
independently of the initial state.Comment: 10 pages, 12 figures, revtex4, submited to PR
The effect of functionalizing lipid nanocapsules with NFL-TBS.40-63 peptide on their uptake by glioblastoma cells.
We previously described a neurofilament derived cell-penetrating peptide, NFL-TBS.40-63, that specifically enters in glioblastoma cells where it disturbs the microtubule network both in vitro and in vivo. The aim of this study is to test whether this peptide can increase the targeted uptake by glioblastoma cells of lipid nanocapsules filled with Paclitaxel, and thus can increase their anti-proliferation in vitro and in vivo. Here, using the drop tensiometry we show that approximately 60 NFL-TBS.40-63 peptides can bind to one 50 nm lipid nanocapsule. When nanocapsules are filled with a far-red fluorochrome (DiD) and Paclitaxel, the presence of the NFL-TBS.40-63 peptide increases their uptake by glioblastoma cells in culture as evaluated by FACS analysis, and thus reduces their proliferation. Finally, when such nanocapsules were injected in mice bearing a glioma tumour, they are preferentially targeted to the tumour and reduce its progression. These results show that nanocapsules functionalized with the NFL-TBS.40-63 peptide represent a powerful drug-carrier system for glioma targeted treatment
Testing Gaussianity on Archeops Data
A Gaussianity analysis using a goodness-of-fit test and the Minkowski
functionals on the sphere has been performed to study the measured Archeops
Cosmic Microwave Background (CMB) temperature anisotropy data for a 143 GHz
Archeops bolometer. We consider large angular scales, greater than 1.8 degrees,
and a large fraction of the North Galactic hemisphere, around 16%, with a
galactic latitude b > 15 degrees.
The considered goodness-of-fit test, first proposed by Rayner & Best (1989),
has been applied to the data after a signal-to-noise decomposition. The three
Minkowski functionals on the sphere have been used to construct a chi-square
statistic using different thresholds. The first method has been calibrated
using simulations of Archeops data containing the CMB signal and instrumental
noise in order to check its asymptotic convergence. Two kind of maps produced
with two different map-making techniques (coaddition and Mirage) have been
analysed.
Archeops maps for both Mirage and coaddition map-making, have been found to
be compatible with Gaussianity. From these results we can exclude a dust and
atmospheric contamination larger than 7.8% (90% CL). Also the non-linear
coupling parameter f_{nl} can be constrained to be -800 < f_{nl} < 1100 at the
95% CL and on angular scales of 1.8 degrees. For comparison, the same method
has been applied to data from the NASA WMAP satellite in the same region of
sky. The 1-year and 3-year releases have been used. Results are compatible with
those obtained with Archeops, implying in particular an upper limit for f_{nl}
on degree angular scales.Comment: A&A accepted. The limits on the contamination and the fnl parameter
have been improve
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