5,022 research outputs found
A note on the moving hyperplane method
We give more precision on the regularity of the domain that is needed to have
the monotonicity and symmetry results recently proved by Damascelli and
Pacella, result concerning p-Laplace equations. For this purpose, we study the
continuity and semicontinuity of some parameters linked with the moving
hyperplane method.Comment: 4 pages, 2 figure
Jacobi fields along harmonic 2-spheres in and are not all integrable
In a previous paper, we showed that any Jacobi field along a harmonic map
from the 2-sphere to the complex projective plane is integrable (i.e., is
tangent to a smooth variation through harmonic maps). In this paper, in
contrast, we show that there are (non-full) harmonic maps from the 2-sphere to
the 3-sphere and 4-sphere which have non-integrable Jacobi fields. This is
particularly surprising in the case of the 3-sphere where the space of harmonic
maps of any degree is a smooth manifold, each map having image in a totally
geodesic 2-sphere.Comment: 43 pages. Some typos corrected; introduction expande
Magnetic and structural properties of nanocrystalline PrCo
The structure and magnetic properties of nanocrystalline PrCo obtained
from high energy milling technique are investigated by X-ray diffraction, Curie
temperature determination and magnetic properties measurements are reported.
The as-milled samples have been annealed in a temperature range of 1023 K to
1273 K for 30 mn to optimize the extrinsic properties. The Curie temperature is
349\,K and coercive fields of 55\,kOe at 10\,K and 12\,kOe at 293\,K are
obtained on the samples annealed at 1023\,K. A simulation of the magnetic
properties in the framework of micromagnetism has been performed in order to
investigate the influence of the nanoscale structure. A composite model with
hard crystallites embedded in an amorphous matrix, corresponding to the
as-milled material, leads to satisfying agreement with the experimental
magnetization curve. [ K. Younsi, V. Russier and L. Bessais, J. Appl. Phys.
{\bf 107}, 083916 (2010)]. The microscopic scale will also be considered from
DFT based calculations of the electronic structure of Co compounds,
where = (Y, Pr) and = 2,3 and 5.Comment: To be published in J. Phys.: Conference Series in the JEMS 2010
special issue. To be found once published at
http://iopscience.iop.org/1742-659
ORIGAMIX, a CdTe-based spectro-imager development for nuclear applications
The Astrophysics Division of CEA Saclay has a long history in the development
of CdTe based pixelated detection planes for X and gamma-ray astronomy, with
time-resolved imaging and spectrometric capabilities. The last generation,
named Caliste HD, is an all-in-one modular instrument that fulfills
requirements for space applications. Its full-custom front-end electronics is
designed to work over a large energy range from 2 keV to 1 MeV with excellent
spectroscopic performances, in particular between 10 and 100 keV (0.56 keV FWHM
and 0.67 keV FWHM at 13.9 and 59.5 keV). In the frame of the ORIGAMIX project,
a consortium based on research laboratories and industrials has been settled in
order to develop a new generation of gamma camera. The aim is to develop a
system based on the Caliste architecture for post-accidental interventions or
homeland security, but integrating new properties (advanced spectrometry,
hybrid working mode) and suitable for industry. A first prototype was designed
and tested to acquire feedback for further developments. In this study, we
particularly focused on spectrometric performances with high energies and high
fluxes. Therefore, our device was exposed to energies up to 700 keV (133Ba,
137Cs) and we measured the evolution of energy resolution (0.96 keV at 80 keV,
2.18 keV at 356 keV, 3.33 keV at 662 keV). Detection efficiency decreases after
150 keV, as Compton effect becomes dominant. However, CALISTE is also designed
to handle multiple events, enabling Compton scattering reconstruction, which
can drastically improve detection efficiencies and dynamic range for higher
energies up to 1408 keV (22Na, 60Co, 152Eu) within a 1-mm thick detector. In
particular, such spectrometric performances obtained with 152Eu and 60Co were
never measured before with this kind of detector.Comment: Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment. Available
online 9 January 2015, ISSN 0168-9002
(http://www.sciencedirect.com/science/article/pii/S0168900215000133).
Keywords: CdTe; X-ray; Gamma-ray; Spectrometry; Charge-sharing; Astrophysics
Instrumentation; Nuclear Instrumentation; Gamma-ray camera
Radial Distributions of Coronal Electron Temperatures: specificities of the DYN model
This paper is a follow up of the article where Lemaire and Stegen (2016)
introduced their DYN method to calculate coronal temperature profiles from
given radial distributions of the coronal and solar wind (SW) electron
densities. Several such temperature profiles are calculated and presented
corresponding to a set of given empirical density models derived from eclipse
observations and in-situ measurements of the electron density and bulk velocity
at 1 AU. The DYN temperature profiles obtained for the equatorial and polar
regions of the corona challenge the results deduced since 1958 from singular
hydrodynamical models of the SW. In these models - where the expansion velocity
transits through a singular saddle point - the maximum coronal temperature is
predicted to be located at the base of the corona, while in all DYN models the
altitude of the maximum temperature is found at significantly higher altitudes
in the mid-corona. Furthermore, the maximum of the DYN-estimated temperatures
is found at much higher altitudes over the polar regions and coronal holes,
than over the equator. However, at low altitudes, in the inner corona, the DYN
temperatures are always smaller at high latitudes, than at low equatorial
latitudes. This appears well in agreement with existing coronal hole
observations. These findings have serious implications on the open questions:
what is the actual source of the coronal heating, and where is the maximum
energy deposited within the solar corona?Comment: 13 pages, 3 figures. Submitted to the Solar Physics journa
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