1,672 research outputs found
Nonlinear optics in Xe-filled hollow-core PCF in high pressure and supercritical regimes
Supercritical Xe at 293 K offers a Kerr nonlinearity that can exceed that of
fused silica while being free of Raman scattering. It also has a much higher
optical damage threshold and a transparency window that extends from the UV to
the infrared. We report the observation of nonlinear phenomena, such as
self-phase modulation, in hollow-core photonic crystal fiber filled with
supercritical Xe. In the subcritical regime, intermodal four-wave-mixing
resulted in the generation of UV light in the HE12 mode. The normal dispersion
of the fiber at high pressures means that spectral broadening can clearly
obtained without influence from soliton effects or material damage
Inelastic X-ray scattering from valence electrons near absorption edges of FeTe and TiSe
We study resonant inelastic x-ray scattering (RIXS) peaks corresponding to
low energy particle-hole excited states of metallic FeTe and semi-metallic
TiSe for photon incident energy tuned near the absorption edge of
Fe and Ti respectively. We show that the cross section amplitudes are well
described within a renormalization group theory where the effect of the core
electrons is captured by effective dielectric functions expressed in terms of
the the atomic scattering parameters of Fe and Ti. This method can be
used to extract the dynamical structure factor from experimental RIXS spectra
in metallic systems.Comment: 6 pages, 4 figure
Damage-free single-mode transmission of deep-UV light in hollow-core PCF
Transmission of UV light with high beam quality and pointing stability is
desirable for many experiments in atomic, molecular and optical physics. In
particular, laser cooling and coherent manipulation of trapped ions with
transitions in the UV require stable, single-mode light delivery. Transmitting
even ~2 mW CW light at 280 nm through silica solid-core fibers has previously
been found to cause transmission degradation after just a few hours due to
optical damage. We show that photonic crystal fiber of the kagom\'e type can be
used for effectively single-mode transmission with acceptable loss and bending
sensitivity. No transmission degradation was observed even after >100 hours of
operation with 15 mW CW input power. In addition it is shown that
implementation of the fiber in a trapped ion experiment significantly increases
the coherence times of the internal state transfer due to an increase in beam
pointing stability
Geometric optics and instability for semi-classical Schrodinger equations
We prove some instability phenomena for semi-classical (linear or) nonlinear
Schrodinger equations. For some perturbations of the data, we show that for
very small times, we can neglect the Laplacian, and the mechanism is the same
as for the corresponding ordinary differential equation. Our approach allows
smaller perturbations of the data, where the instability occurs for times such
that the problem cannot be reduced to the study of an o.d.e.Comment: 22 pages. Corollary 1.7 adde
Hybrid-Entanglement in Continuous Variable Systems
Entanglement is one of the most fascinating features arising from
quantum-mechanics and of great importance for quantum information science. Of
particular interest are so-called hybrid-entangled states which have the
intriguing property that they contain entanglement between different degrees of
freedom (DOFs). However, most of the current continuous variable systems only
exploit one DOF and therefore do not involve such highly complex states. We
break this barrier and demonstrate that one can exploit squeezed cylindrically
polarized optical modes to generate continuous variable states exhibiting
entanglement between the spatial and polarization DOF. We show an experimental
realization of these novel kind of states by quantum squeezing an azimuthally
polarized mode with the help of a specially tailored photonic crystal fiber
Oligofructose Promotes Satiety in Healthy Human: A Pilot Study.
Objective: The administration of a fermentable dietary fibre (oligofructose) in rats increases satietogenic gut peptides and lowered spontaneous energy intake. The aim of the study was to assess the relevance of those effects of oligofructose on satiety and energy intake in humans. Design: Single-blinded, crossover, placebo-controlled design, pilot study. Subjects: Volunteers included five men and five women aged 21-39 years, BMI ranging from 18.5 to 27.4 kg/m 2 , were randomly assigned as described below. Interventions: Subjects were included in two 2-week experimental phases during which they received either fibre (oligofructose (OFS)) or placebo (dextrine maltose (DM)); a 2-week washout period was included between crossover phases. In total, 8 g OFS or 8 g DM were ingested twice daily (16 g/day in total). Energy intake, hunger, satiety, fullness and prospective food consumption were assessed with analogue scales at the end of each experimental phase. Results: During breakfast, OFS significantly increases the satiety (P ¼ 0.04) without any difference on other sensations as compared to DM treatment periods. After lunch, no significant differences are observed between treatment period. At dinner, OFS significantly increases satiety (P ¼ 0.04), reduces hunger (P ¼ 0.04) and prospective food consumption (P ¼ 0.05). The energy intake at breakfast and lunch are significantly lower (P ¼ 0.01, 0.03, respectively) after OFS treatment than after DM treatment. Total energy intake per day is 5% lower during OFS than in DM period. Conclusion: Oligofructose treatment increases satiety following breakfast and dinner, reduces hunger and prospective food consumption following dinner. This pilot study presents a rationale to propose oligofructose supplements in the management of food intake in overweight and obese patients. Sponsorship: This project is supported by an FSR grant from the Université catholique de Louvain
Implications from the optical to UV flux ratio of FeII emission in quasars
We investigate FeII emission in Broad Line Region (BLR) of AGNs by analyzing
the FeII(UV), FeII(4570) and MgII emission lines in 884 quasars in the Sloan
Digital Sky Survey (SDSS) Quasar catalog in a redshift range of 0.727 < z <
0.804. FeII(4570)/FeII(UV) is used to infer the column density of FeII-emitting
clouds and explore the excitation mechanism of FeII emission lines. As
suggested before in various works, the classical photoionization models fail to
account for FeII(4570)/FeII(UV) by a factor of 10, which may suggest anisotropy
of UV FeII emission; otherwise, an alternative heating mechanism like shock is
working. The column density distribution derived from FeII(4570)/FeII(UV)
indicates that radiation pressure plays an important role in BLR gas dynamics.
We find a positive correlation between FeII(4570)/FeII(UV) and the Eddington
ratio. We also find that almost all FeII-emitting clouds are to be under
super-Eddington conditions unless ionizing photon fraction is much smaller than
that previously suggested. Finally we propose a physical interpretation of a
striking set of correlations between various emission-line properties, known as
``Eigenvector 1''.Comment: 10 pages, 10 figures, accepted for publication in MNRA
Unraveling 5f-6d hybridization in uranium compounds via spin-resolved L-edge spectroscopy
FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESThe multifaceted character of 5f electrons in actinide materials, from localized to itinerant and in between, together with their complex interactions with 6d and other conduction electron states, has thwarted efforts for fully understanding this class of compounds. While theoretical efforts abound, direct experimental probes of relevant electronic states and their hybridization are limited. Here we exploit the presence of sizable quadrupolar and dipolar contributions in the uranium L-3-edge X-ray absorption cross section to provide unique information on the extent of spin-polarized hybridization between 5f and 6d electronic states by means of X-ray magnetic circular dichroism. As a result, we show how this 5f-6d hybridization regulates the magnetism of each sublattice in UCu2Si2 and UMn2Si2 compounds, demonstrating the potentiality of this methodology to investigate a plethora of magnetic actinide compounds.816FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES10/19979-92013/22436-52014/05480-32014/26620-8Sem informaçãoWe are thankful to Roberto Caciuffo and Gerry Lander for discussions and comments on the manuscript. We thank Jose Carlos Botelho Monteiro for providing one of the UMn2Si2 samples. Work at Argonne is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC-02-06CH11357. Work at LNLS is supported by the Brazilian ministry of science and technology. This research was supported by FAPESP grants 2013/22436-5, 2014/05480-3, 10/19979-9, and 2014/26620-8. R.D.d.R. thanks the funding for his Ph.D. fellowship from CAPES brazilian agency
Direct observation of electron density reconstruction at the metal-insulator transition in NaOsO3
5d transition metal oxides offer new opportunities to test our understanding
of the interplay of correlation effects and spin-orbit interactions in
materials in the absence of a single dominant interaction. The subtle balance
between solid-state interactions can result in new mechanisms that minimize the
interaction energy, and in material properties of potential use for
applications. We focus here on the 5d transition metal oxide NaOsO3, a strong
candidate for the realization of a magnetically driven transition from a
metallic to an insulating state exploiting the so-called Slater mechanism.
Experimental results are derived from non-resonant and resonant x-ray single
crystal diffraction at the Os L-edges. A change in the crystallographic
symmetry does not accompany the metal-insulator transition in the Slater
mechanism and, indeed, we find no evidence of such a change in NaOsO3. An
equally important experimental observation is the emergence of the (300) Bragg
peak in the resonant condition with the onset of magnetic order. The intensity
of this space-group forbidden Bragg peak continuously increases with decreasing
temperature in line with the square of intensity observed for an allowed
magnetic Bragg peak. Our main experimental results, the absence of crystal
symmetry breaking and the emergence of a space-group forbidden Bragg peak with
developing magnetic order, support the use of the Slater mechanism to interpret
the metal-insulator transition in NaOsO3. We successfully describe our
experimental results with simulations of the electronic structure and, also,
with an atomic model based on the established symmetry of the crystal and
magnetic structure.Comment: 6 figure
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