32 research outputs found
A hot spot of olive biodiversity in the Tunisian oasis of degache
Tunisia is one of the world's largest producers of olive oil, and it preserves pools of olive genetic diversity that are still unexplored. A recent prospection and collection program of the National Gene Bank of Tunisia (NGBT) focused on the vast oasis of Degache, in the south west part of Tunisia, where 47 samples were collected and genetically characterized through simple sequence repeat (SSR) markers. Identification and authentication of genotypes were obtained through comparison with reference cultivars belonging to the Olive National Collection of Tunisia (IOC) and with cultivars from Algeria, Italia, Syria and Lebanon. Degache olive genotypes showed large genetic variability, a significant diversity from the reference germplasm, and a clear differentiation from modern varieties. The population structure analysis identified four gene pools characterizing genotypes from different area of origin. Two gene pools appear to be more represented in germplasm from southern Tunisia, where environmental conditions at critical plant development phases, are harsher. This suggests that this germplasm might present traits of adaptation useful for breeding to improve resilience to abiotic stresses. Our results will support ex situ and in situ conservation activities of Tunisian olive germplasm pursued by the National Gene Bank of Tunisia
Structural Characterization of Magnetic Nano-particles Suspensions, Using Magnetic Measurements
P curves, Magnetic fluids, Ferrofluids, Nanostructural characterization, Magnetic powders, Hysteresis curve, Magnetic nanocomposite materialsThe paper describes some characteristics of the “P” curves for structural characterization of magnetic nano-particles suspensions (complex fluids, complex powders, complex composite materials, or living biological materials having magnetic properties). In the case of these materials, the magnetic properties are conferred to various carrier liquids by artificially integrating in their structure ferromagnetic particles of different sizes. The magnetic properties are usually shown by the hysteresis curve. The structure can be seen on (electronic) micrography. The P curves offer another possibility to determine the structure of the magnetic component of a complex fluid by numerical analysis of the magnetization curve experimentally obtained. The paper presents a detailed approach of the P curves and some limitations in their use
Fabrication and characterization of micro-inductors deposited on magnetic thin and thick layers
This paper presents two fabrication techniques of spiral integrated inductors based on magnetic materials. For the first one, the magnetic core is a thin film deposited by RF magnetron sputtering, for the second technique the magnetic core is a thick layer of YIG obtained by micromachining. The addition of the magnetic material is expected to improve the performances of the integrated structure with electromagnetic shield. Low and high frequency equipment are used to characterize the manufactured components. A good correlation is obtained between the results by simulation and measurements for the two manufacturing techniques. These results show that the inductance increases when the thickness of the magnetic layer increases, we can double the inductance value for a thickness sufficiently high
Comparison between a magneto-optical method and Fannin's technique for measuring Brown's relaxation frequency of ferrofluids
International audienc
Dielectric study of primary amines from room temperature down to −180 °C and from 10 kHz up to 35 GHz
The aim of this paper is to present the NH2 dielectric behaviour in the
primary amines for the importance it bears in the interaction of aminoacids and
proteins and their influence in the electric conduction processes. For that, the
dielectric properties of 1-propylamine, 1-butylamine and 1-pentylamine have been
studied. Measurements were performed between room temperature and −180 °C in
the low frequency range and micro-waves measurements were done between −40 °C
and 25 °C. The isofrequency recordings of dispersion
ε′ and absorption ε′′,
for these three primary amines, show
clearly the relaxations and the effect of the aliphatic chain length
Physico-chemical characterization of multilayer YIG thin film deposited by rf sputtering
Yttrium iron garnet (YIG) film made as a magneto-optical medium suffers from
the problem of crack formation, caused by the heating process. YIG thin film
is deposited by radio frequency rf magnetron sputtering; the obtained layer
is amorphous and it needs annealing to be crystallized. After heat-treatment
at 740 ○C of the sample realized on quartz substrate, we observe cracks
on the entire film surface. This is due to the large difference between the
thermal expansion coefficient (5.5 ×10-7 K-1 for quartz and 10 ×
10-6 K-1 for YIG). In this paper we present a new fabrication
method to reduce this problem, we make a multilayer to obtain at the end a
uniformly unique layer with excellent crystalline structure. Such films have
the possibility to reach a thickness of 500 nm. YIG films have been studied
by Rutherford backscattering spectrometry (RBS), optic ellipsometry and the
scan electron microscope. The RBS spectra were collected in channelling
geometry with incident particles energy 2 MeV and 3.5 MeV. The thickness and
the stoichiometric value of the thin films have been evaluated. Simulation
of all spectra indicates a constant composition. Ellipsometry method is well
adapted to model the thin film structure layers, and to measure the
thickness of the film and the complex index of refraction. The theoretical
ellipsometric value of the index of refraction is (2.22) while the
experimental value is ranging from 2.2 to 2.3 for a wavelength of 1550 nm
Performances of interleaved and Face to Face integrated magnetic transformers
Currently, most of integrated transformers are fabricated without magnetic core. In order to reduce the size and to improve their performances, we were interested in the study of integrated transformers based of thin ferrite films. Interleaved and Face to Face structures were simulated using the Ansoft HFSS simulator over a wide range of frequency (up to 100MHz). A high frequency electrical model has been defined to determine the main characteristics of the transformer and particularly the interwinding capacitance and coupling factor between primary and secondary windings. The simulation results allowed us to determine the geometrical dimensions of these structures in order to optimize the magnetic coupling coefficient and to minimize inter winding capacitance