Search results for "electromagnetic [radiation]"
showing 10 items of 873 documents
Study of Structure–Third-Order Susceptibility Relation of Indandione Derivatives
2016
By using the Z-scan method we studied the third-order nonlinear optical parameters of several aminobenziliden-1,3-indandione (ABI) derivatives that have previously been shown to own second-order nonlinear optical properties. Measurements were carried out using two 1064 nm Nd:YAG lasers with picosecond (ps) and nanosecond (ns) pulse widths, respectively. When ns laser was employed in the Z-scan setup, a strong thermal lensing took place resulting in severe overestimation of optical Kerr coefficients. Due to this reason the ps laser was employed to evaluate correct magnitude of Kerr effect. For investigated organic molecules, experimental results show that two-photon absorption at 1064 nm is …
Electromagnetic response of LaO_0.94F_0.06FeAs: AC susceptibility and microwave surface resistance
2009
We discuss on the electromagnetic response of a polycrystalline sample of LaO_0.94F_0.06FeAs exposed to DC magnetic fields up to 10 kOe. The low- and high-frequency responses have been investigated by measuring the AC susceptibility at 100 kHz and the microwave surface resistance at 9.6 GHz. At low as well as high DC magnetic fields, the susceptibility strongly depends on the amplitude of the AC driving field, highlighting enhanced nonlinear effects. The field dependence of the AC susceptibility exhibits a magnetic hysteresis that can be justified considering the intragrain-field-penetration effects on the intergrain critical current density. The microwave surface resistance exhibits a cloc…
Lanthanide-doped Y3Ga5O12 garnets for nanoheating and nanothermometry in the first biological window
2018
Abstract Absorption and luminescence spectra in the first biological window of Nd3+ single-doped and Er3+-Yb3+ co-doped Y3Ga5O12 nano-garnets have been studied to evaluate their potential use as simultaneous optical nanoheaters and nanothermometers in biomedicine. Nd3+-doped nano-garnets uses the 808 nm laser radiation, resonant with the largest absorption peak of the 4I9/2 → 4F5/2 transition, for both heating the nanoparticle and populating the 4F3/2 emitting level. Changes in the relative intensities of different emission peaks between Stark levels of the 4F3/2 (R1,2)→4I9/2 (Z1-5) transition can be directly related to the temperature of the nano-garnet. On the other hand, the Yb3+/Er3+com…
Influence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence
2011
International audience; Confocal microscopy luminescence measurements were applied to study the X-ray radiation response of Er/Yb-doped optical fibers in connection with H2 pre-loading and with the addition of another lanthanide element (Cerium) in the core composition. Laser excitations at 488 nm and 325 nm allow deriving the emission and absorption pattern of Er3+, the latter derived from the dips appearing in a wide luminescence band related to defects in silica. We found that the luminescence spectrum of the X-irradiated Er/Yb-doped core fiber evidences an increase in the emission intensity around 520 and 660 nm; in contrast, no changes are induced by radiation neither after H2 pre-load…
On the topographic and energetic surface modifications induced by laser treatment of metallic substrates before plasma spraying
2003
Abstract Laser surface cleaning has been proven as a very suitable technique for the substitution of some surface preparation steps, such as wet cleaning and grit blasting. The mechanisms involved in short pulsed laser ablation include the absorption of the laser light and conversion into heat via collisional processes. Ejection of matter is achieved either by direct vaporization or hydrodynamical sputtering. This article aims at clarifying the laser–matter interaction mechanisms and effects on metallic materials for different surfaces initial roughness and laser beam energy densities. Both topographic and energetic modifications are investigated by SEM observations, roughness characterizat…
Temperature-dependent EXAFS study of the local structure and lattice dynamics in cubic Y2O3
2016
The local structure and lattice dynamics in cubic Y2O3were studied at the YK-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.
Time-variations of zeroth-order vegetation absorption and scattering at L-band
2021
Abstract Surface soil moisture and vegetation optical depth (VOD), as an indicator of vegetation wet biomass, from passive microwave remote sensing have been increasingly applied in global ecology and climate research. Both soil moisture and VOD are retrieved from satellite brightness temperature measurements assuming a zeroth order radiative transfer model, commonly known as the tau-omega model. In this model the emission of a vegetated surface is dependent on soil moisture, vegetation absorption and vegetation scattering. Vegetation scattering is normally represented by the single scattering albedo, ω, and is commonly assumed to be a time-invariant calibration parameter to achieve high ac…
Relaxation Dynamics of Cr(acac)3 Probed by Ultrafast Infrared Spectroscopy
2007
Ultrafast infrared spectroscopy is used to probe the dynamics of Cr(acac)3 upon ligand field (400 nm) and charge transfer state (345 nm) excitation. At both pump wavelengths, the ground state absorption bands are strongly bleached at zero delay, and new broad transient absorption bands appear red shifted from the bleached bands. Recovery of ground state bleach is dominated by a fast time constant (15 ps), while a small percentage recovers within 760−900 ps. Despite the extensive studies on Cr(acac)3 photophysics, the fast recovery of the ground state as a major channel is reported here for the first time. As a general result, the present communication emphasizes the great value of ultrafast…
Light Dark Matter Search with Ionization Signals in XENON1T
2019
We report constraints on light dark matter (DM) models using ionization signals in the XENON1T experiment. We mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22±3) tonne day. Above ∼0.4 keVee, we observe <1 event/(tonne day keVee), which is more than 1000 times lower than in similar searches with other detectors. Despite observing a higher rate at lower energies, no DM or CEvNS detection may be claimed because we cannot model all of our backgrounds. We thus exclude new regions in the parameter spaces for DM-nucleus scattering for DM masses mχ within 3–6 GeV/c2, DM-electron scattering for mχ>30 MeV/c2, a…
Human Hsp60 with Its Mitochondrial Import Signal Occurs in Solution as Heptamers and Tetradecamers Remarkably Stable over a Wide Range of Concentrati…
2014
It has been established that Hsp60 can accumulate in the cytosol in various pathological conditions, including cancer and chronic inflammatory diseases. Part or all of the cytosolic Hsp60 could be naive, namely, bear the mitochondrial import signal (MIS), but neither the structure nor the in solution oligomeric organization of this cytosolic molecule has still been elucidated. Here we present a detailed study of the structure and self-organization of naive cytosolic Hsp60 in solution. Results were obtained by different biophysical methods (light and X ray scattering, single molecule spectroscopy and hydrodynamics) that all together allowed us to assay a wide range of concentrations of Hsp60…