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High resolution neutron diffraction patterns of BaCexZr1−xO3 (x = 0, 0.1, 0.4,
0.8) were obtained at various temperatures. The phase diagram that was deduced from Raman
measurements has been confirmed. Structural transitions occur in a fixed order
c-Pm3m as a function of temperature or composition. For BaCeO3, the
large volume change that has been previously claimed at the Imma-R
c transition has
been revisited and found inconsistent. For a given composition, the cell volume increases
when temperature increases, but the MO6 (M=Ce-Zr) octahedron volume decreases. It is
shown that the ratio of the cell volume to the octahedron volume is a good indicator of the
phase transitions. Transitions occur at fixed values (5.77, 5.80 and 6 for the Pnma-Imma,
c and R
c-Pm3m transitions respectively) independently of
The evolution of the passivating layer (during the first
reduction/reoxidation cycle, in function of the number of reduction/reoxidation
cycles and with the storage of the electrode in the electrolyte) formed at the
surface of a lithiated carbon electrode in LiCF3SO3/carbonates mixture electrolyte
has been followed by using 1 MeV 4He+ induced Rutherford Backscattering
Spectrometry (RBS). Two RBS simulation codes "RUMP" and "PERM" , whose approaches
are different, have been applied to the treatment of the RBS data and have allowed
to obtain informations about the structure (thickness and atomic elemental
composition) of the passivating layer. These two codes provide similar results. The
passivating layer has a thickness in the range 20-30 nm. Its structure appears to
be complex with the presence of two different sublayers respectively composed of the
reduction products of the salt in the inner sublayer (with the main presence of
fluorine and sulphur indicating the possible existence of LiF and Li2S) and
reduction products of the solvents in the outer sublayer (with a high concentration
in oxygen indicating the presence of Li2CO3 and RCO3Li where R is an alkyl
A luminescent study under selective photonic excitation has established the
presence of three different kinds of Ce3+ centres in SrS atomic layer
epitaxy thin films: one in a regular sulfur octahedral sites and two others in
lower symmetry. These last sites shift the emission spectra towards the green.
High thermal annealing up to 750 °C improves the crystallinity of the
SrS:Ce layer by converting low symmetry Ce3+ sites in regular octahedral
sites and decreasing the density of defects. These two effects lead to efficient
PL layers with a good blue chromaticity.
Dielectric and noise measurements versus frequency have been performed on a liquid
crystal in the paraelectric SA and ferroelectric
phases. A confrontation of
these measurements is presented on the basis of the fluctuation-dissipation theorem
which shows that these techniques both give similar results linked to the
observation of the classical soft mode and Goldstone mode in the SA and
A pulse is solution of a boundary-initial value problem for
the wave equation.We investigate the propagation in the z-direction of
a Maxwell-Hopkinson dielectric of three kinds of pulses launched from
the z = 0 plane at some time: harmonic plane wave, Bessel wave,
distortion-free progressing wave. We prove that at high frequency,
and as soon as the transient state has died out, these pulses propagate
with an exponential attenuation factor in the direction of propagation.
The Dulkyn interferometer in Kazan is an active ring laser where the light
propagates along two different paths. It has been developed with the idea
that it could detect low frequency gravitational waves on Earth.
Considering Dulkyn as a detector of periodic strains of order of
h ~ 10−22 at low frequencies (10−3 Hz−10−5 Hz) we
calculate that 30 W is the order of magnitude of the optical power
necessary to beat the photon noise in the case of a long observation time
(T = 4 months) and a reasonable signal to noise ratio (r = 3). We estimate
that the displacement noise of the mirrors must not exceed 5×10−19m/
Dulkyn is also sensitive to accelerations and rotations. The acceleration
noise does not seem to be troublesome
), but the angular velocity noise must be
less than 5×10−11 s−1/
The maximum strain (10−22) is obtained with free (pendulous) mirrors.
Out of resonance, the strain is many orders of magnitude smaller when the
mirrors are fixed on a rigid support. Such a case would rule out the
possibility of a detection. As a conclusion we emphasize that the Dulkyn
design does not bring any decisive improvement for the detection of low
frequency gravitational waves on Earth.
We have developed a model for the calculation of the induced current due to an electron beam with an
extended generation profile. Added to the absorbed and diffuse electrons in the depth distribution, the
generation profile takes into account the lateral diffusion.
The analytical expression of the electron beam induced current (EBIC) is obtained by solving the continuity
equation in permanent regime by the Green function method.
The induced current profile, obtained in the case of a ternary component
(Ga0.7Al0.3As:N+/Ga0.7Al0.3As:P) sulfur doped and prepared by organometallic
compounds phase vapor epitaxy method, is compared to the theoretical profiles whose analytical expressions
are given by Van Roosbroeck and Bresse.
The experimental current profile, measured by S.E.M provided us to calculate the diffusion length of the
minority carriers: Lp = 1 µm in the N region and Ln = 1.80 µm in the P
region of the ternaire component. The theoretical curve obtained from the proposed model is in good
agreement with the experimental one for a surface recombination velocity of 106 cm s−1. Our results
are found to be consistent compared to those obtained by other experimental techniques using the same
We have tried to understand the role of cellular tone (or internal tension mediated
by actin filaments) and interactions with the microenvironment on cellular stiffness. For
this purpose, we compared the apparent elasticity modulus of a 30-element tensegrity
structure with cytoskeleton stiffness measured in subconfluent and confluent adherent cells
by magnetocytometry, assessing the effect of changing cellular tone by treatment with
cytochalasin D. Intracellular and extracellular mechanical interactions were analyzed on the
basis of the non-dimensional relationships between the apparent elasticity modulus of the
tensegrity structure normalized by Young's modulus of the elastic element versus: (i)
element size, (ii) internal tension, and (iii) number of spatially fixed nodes, for small
deformation conditions. Theoretical results and rigidity measurements in adherent cells
consistently showed that higher cellular tone and stronger interdependencies with cellular
environment tend to increase cytoskeleton stiffness. Visualization of the actin lattice
before and after depolymerization by cytochalasin D tended to confirm the geometrical and
mechanical assumptions supported by analysis of the present model.
Temperature is an important parameter for industrial process control. With
the usual methods we obtain only an invasive or superficial information about
temperature. Microwave radiometry is a non-invasive way to determine the temperature
within dissipative body. This paper presents the design of a new radiometer. With this
system, the radiometric temperature is independent of the reflection coefficient of the
sensor. A simplified calibration takes into account insertion losses of the microwave
elements and the frequency bandwidth has been greatly reduced to eliminate the
unwanted electromagnetic noise.
This article presents an application of a speckle interferometry technique with
doubling, called "shearography". This technique can be used for near real time
imaging of Lamb waves in continuous or burst modes, revealing the presence of
delaminations in a carbon epoxy plate. The amplitude of the displacements is
measured with a typical uncertainty of the order of 1 nm. The nominal Lamb wave can
be suppressed from the shearographic image by optical filtering, to show only the
wave interaction with any defects that may exist in the plate. This method is
especially advantageous for non-destructive testing.
The study concerns remote controlled sensors, associating micro-mechanical and microwave data communication
functions. A radio link can be used to transmit information from the sensor as well as to provide internal
power supply. Applications include Wireless Sensor Networks projects. An important operation is performed
through a passive microwave frequency shifter used for retransmission. Two structures of this frequency
shifter using silicon membrane micro-mechanical capacitors are described, with further details concerning
the optimisation of the dimensions using electro-mechanical modellisation, the problems in technological
silicon implantation, and some first experimental results.
The characteristics of the various modes of acoustic waves (velocity, attenuation,
efficiency) radiated towards the focused sensor of an acoustic microscope are
related to the acoustic properties of the coupling fluid. The aqueous solutions of
electrolytes are suitable as coupling fluids because their acoustic properties can
be adjusted owing to the choice of the nature and of the concentration of the
dissolved ions. By adjusting the properties of the couplant, the performances of the
sensors of the acoustic microscopes can be extended. The image contrasts and the
accuracy of measurements of the acoustic waves velocity are improved, the radiation
of the chosen modes are enhanced and very high frequencies can be used.