We consider Fourier multipliers in
R
2
with singularities on certain curves, which are closely related to the Bochner–Riesz Fourier multipliers. We prove weighted inequalities and vector valued ...inequalities for the Fourier multiplier operators which generalize some known results.
Dissimilar welds between Al alloy and stainless steel were produced with an ultrasonic welding technique. The weld strength increased with the welding energy. The welds produced with sufficiently ...high energy exhibited nugget pull-out failure of the Al alloy during the lap shear strength test. The welds with weld energies of more than 1.05kJ fractured in the base metal and were severely deformed by the ultrasonic vibration, and recrystallization occurred around the weld interface owing to the shear deformation and heating during the ultrasonic welding.
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Transient currents in AlGaN/GaN High Electron Mobility Transistors (HEMTs) induced by focused ion beams are measured. Enhanced charge collection occurs in the on- and pinch-off states of AlGaN/GaN ...HEMTs. The first-order mechanism of enhancement is associated with bipolar and back-channel effects. In addition, we suggest that the temporal positive charge buildup contributes to the enhanced charge collection. The effect of displacement damage on the enhanced charge collection is also discussed.
Interaction of light with an excited free-electron gas is a fundamental process spanning a large variety of fields in physics. The advent of femtosecond laser pulses and extreme-ultraviolet sources ...allowed one to put theoretical models to the test. Recent experimental and theoretical investigations of nonequilibrium aluminum, which is considered to be a good real-world representation of an ideal free-electron metal, showed that, despite significant progress, the transient hot-electron/cold-ion state is not well understood. In particular, the role of plasmon broadening, screening, and electron degeneracy remains unclear. Here, we experimentally investigate the free-free opacity in aluminum on the few-femtosecond timescale at laser intensities close to the damage threshold. Few-femtosecond time resolution allows us to track the purely electronic contribution to nonequilibrium absorption and unambiguously separate it from the slower lattice contribution. We support the experiments with ab initio calculations and a nearly free electron model in the Sommerfeld expansion. We find that the simplest independent-particle model with a fixed band structure is sufficient to explain the experimental findings without the need to include changes in screening or electron scattering, contrasting previous observations in3dtransition metals. We further find that electronic heating of a free-electron gas shifts the spectral weight of the absorption to higher photon energies, and we are able to distinguish the influence of the population change and the chemical potential shift based on the comparison of ab initio calculations to a simplified free-electron model. Our findings provide a benchmark for further investigations and modeling of dense nonequilibrium plasma under even more extreme conditions.
The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how ...excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe
, that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal M. Volkov
,
, 1145-1149 (2019) carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials.
Summary
Root amputation, extraction of a single tooth, bone loss or severe tooth mobility, and an unclosed wound were significantly associated with increased risk of developing medication-related ...osteonecrosis of the jaw (MRONJ). We recommend a minimally traumatic extraction technique, removal of any bone edges, and mucosal wound closure as standard procedures in patients receiving bisphosphonates.
Introduction
Osteonecrosis of the jaws can occur following tooth extraction in patients receiving bisphosphonate drugs. Various strategies for minimizing the risk of MRONJ have been advanced, but no studies have comprehensively analyzed the efficacy of factors such as primary wound closure, demographics, and drug holidays in reducing its incidence. The purpose of this study was to retrospectively investigate the relationships between these various risk factors after tooth extraction in patients receiving oral bisphosphonate therapy.
Methods
Risk factors for MRONJ after tooth extraction were evaluated using univariate and multivariate analysis. All patients were investigated with regard to demographics; type and duration of oral bisphosphonate use; whether they underwent a discontinuation of oral bisphosphonates before tooth extraction (drug holiday), and the duration of such discontinuation; and whether any additional surgical procedures (e.g., incision, removal of bone edges, root amputation) were performed.
Results
We found that root amputation (OR = 6.64), extraction of a single tooth (OR = 3.70), bone loss or severe tooth mobility (OR = 3.60), and an unclosed wound (OR = 2.51) were significantly associated with increased risk of developing MRONJ.
Conclusions
We recommend a minimally traumatic extraction technique, removal of any bone edges, and mucosal wound closure as standard procedures in patients receiving bisphosphonates. We find no evidence supporting the efficacy of a pre-extraction short-term drug holiday from oral bisphosphonates in reducing the risk of MRONJ.
We theoretically investigate the dynamical Franz-Keldysh effect in femtosecond time resolution, that is, the time-dependent modulation of a dielectric function at around the band gap under an ...irradiation of an intense laser field. We develop a pump-probe formalism in two distinct approaches: first-principles simulation based on real-time time-dependent density functional theory and analytic consideration of a simple two-band model. We find that, while time-average modulation can be reasonably described by the static Franz-Keldysh theory, a remarkable phase shift is found to appear between the dielectric response and the applied electric field.
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