169 research outputs found
Structural and rheological properties of medium-chain triacylglyceride oleogels
This research studied the effect of gelator molecules on structural properties of oleogels containing medium-chain triacylglycerides (MCTs). To this aim, a large selection of gelators (rapeseed wax RAW, rice wax RW, sunflower wax SW, beeswax BW, monoglycerides MG, and \u3b3-oryzanol and \u3b2-sitosterol mixture \u3b3+\u3b2) at increasing concentrations (5\u201315% w/w) was considered. Results showed that RAW was not able to structure MCT at any concentration. However, addition of 5% (w/w) of MG, SW and BW resulted to a self-standing gel. Regarding \u3b3+\u3b2 and RW, gel structures were generated at 10% (w/w). By increasing the concentration, a reinforcement of the network strength was highlighted by the progressive increase of the rheological parameters. The strongest oleogel obtained by \u3b3+\u3b2 at 10% (w/w) and further BW and RW at 15% (w/w) concentration. These findings could provide interesting information in the choice of the best performing MCT structuring agent for intended food applications
Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopy
We employ Faraday and Kerr effect spectroscopy in the infrared range to
investigate the electronic structure of Ga1-xMnxAs near the Fermi energy. The
band structure of this archetypical dilute-moment ferromagnetic semiconductor
has been a matter of controversy, fueled partly by previous measurements of the
unpolarized infrared absorption and their phenomenological impurity-band
interpretation. The infrared magneto-optical effects we study arise directly
from the spin-splitting of the carrier bands and their chiral asymmetry due to
spin-orbit coupling. Unlike the unpolarized absorption, they are intimately
related to ferromagnetism and their interpretation is much more microscopically
constrained in terms of the orbital character of the relevant band states. We
show that the conventional theory of the disordered valence band with dominant
As p-orbital character and coupled by kinetic-exchange to Mn local moments
accounts semi-quantitatively for the overall characteristics of the measured
infrared magneto-optical spectra.Comment: 4 pages 3 figure
Review of the ELI-NP-GBS low level rf and synchronization systems
The Gamma Beam System (GBS) of ELI-NP is a linac based gamma-source in construction at Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy and with intensity and brilliance well beyond the state of the art will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and a 515 nm intense laser pulse. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation at 100 Hz repetition rate. A total of 13 klystrons, 3 S-band (2856 MHz) and 10 C-band (5712 MHz) will power a total of 14 Travelling Wave accelerating sections (2 S-band and 12 C-band) plus 3 S-band Standing Wave cavities (a 1.6 cell RF gun and 2 RF deflectors). Each klystron is individually driven by a temperature stabilized LLRF module, for a maximum flexibility in terms of accelerating gradient, arbitrary pulse shaping (e.g. to compensate beam loading effects in multi-bunch regime) and compensation of long-term thermal drifts. In this paper, the whole LLRF system architecture and bench test results, the RF reference generation and distribution together with an overview of the synchronization system will be described
Internal Transitions of Two-Dimensional Charged Magneto-Excitons X-: Theory and Experiment
Internal spin-singlet and spin-triplet transitions of charged excitons X- in
magnetic fields in quantum wells have been studied experimentally and
theoretically. The allowed X- transitions are photoionizing and exhibit a
characteristic double-peak structure, which reflects the rich structure of the
magnetoexciton continua in higher Landau levels (LL's). We discuss a novel
exact selection rule, a hidden manifestation of translational invariance, that
governs transitions of charged mobile complexes in a magnetic field.Comment: 4 pages, 2 figures, submitted to Physica
Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction
We measure the Hall conductivity of a two-dimensional electron gas formed at
a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron
resonance frequency by employing a highly sensitive Faraday rotation method
coupled with electrical gating of the sample to change the electron density. We
observe clear plateau-and step-like features in the Faraday rotation angle vs.
electron density and magnetic field (Landau-level filling factor), which are
the high frequency manifestation of quantum Hall plateaus - a signature of
topologically protected edge states. The results are compared to a recent
dynamical scaling theory.Comment: 18 pages, 3 figure
Systematic study of magnetic linear dichroism and birefringence in (Ga,Mn)As
Magnetic linear dichroism and birefringence in (Ga,Mn)As epitaxial layers is
investigated by measuring the polarization plane rotation of reflected linearly
polarized light when magnetization lies in the plane of the sample. We report
on the spectral dependence of the rotation and ellipticity angles in a broad
energy range of 0.12-2.7 eV for a series of optimized samples covering a wide
range on Mn-dopings and Curie temperatures and find a clear blue shift of the
dominant peak at energy exceeding the host material band gap. These results are
discussed in the general context of the GaAs host band structure and also
within the framework of the k.p and mean-field kinetic-exchange model of the
(Ga,Mn)As band structure. We find a semi-quantitative agreement between
experiment and theory and discuss the role of disorder-induced non-direct
transitions on magneto-optical properties of (Ga,Mn)As.Comment: 18 page
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