348 research outputs found
Homogenization and Scattering Analysis of Second-Harmonic Generation in Nonlinear Metasurfaces
We propose an extensive discussion on the homogenization and scattering
analysis of second-order nonlinear metasurfaces. Our developments are based on
the generalized sheet transition conditions (GSTCs) which are used to model the
electromagnetic responses of nonlinear metasurfaces. The GSTCs are solved both
in the frequency domain, assuming an undepleted pump regime, and in the
time-domain, assuming dispersionless material properties but a possible
depleted pump regime. Based on these two modeling approaches, we derive the
general second-harmonic reflectionless and transmissionless conditions as well
as the conditions of asymmetric reflection and transmission. We also discuss
and clarify the concept of nonreciprocal scattering pertaining to nonlinear
metasurfaces
Two new triterpenoid saponins from the leaves of Bupleurum lancifolium (Apiaceae)
Chemical investigation of the leaves of Bupleurum lancifolium led to the isolation and identification of two triterpenoid saponins previously undescribed named 3-O-[α-L-rhamnopyranosyl (1 → 4)-β-D-glucopyranosyl] echinocystic acid 28-O-β-D-glucopyranosyl ester (1) and 3-O-[α-L-rhamnopyranosyl (1 → 4)-β-D-glucopyranosyl] oleanolic acid 28-O-β-D-glucopyranosyl ester (2) along with the two known compounds isorhamnetin 3-rutinoside (3) and rutin (4). Their structures were elucidated by different spectroscopic methods, including HRESIMS analysis as well as 1D and 2D NMR experiments
Selection of Algerian medicinal plants according to a screening of their anti-AGEs properties
International audienc
Screening of anti-AGE properties and dereplication of extracts from algerian medicinal plants
International audienc
Prolate-Spherical Shape Coexistence at N=28 in S
The structure of S has been studied using delayed and
electron spectroscopy at \textsc{ganil}. The decay rates of the 0
isomeric state to the 2 and 0 states have been measured for the
first time, leading to a reduced transition probability
B(E2~:~20= 8.4(26)~efm and a monopole
strength (E0~:~00
=~8.7(7)10. Comparisons to shell model calculations point
towards prolate-spherical shape coexistence and a phenomenological two level
mixing model is used to extract a weak mixing between the two configurations.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Structure of Be probed via secondary beam reactions
The low-lying level structure of the unbound neutron-rich nucleus Be
has been investigated via breakup on a carbon target of secondary beams of
B at 35 MeV/nucleon. The coincident detection of the beam velocity
Be fragments and neutrons permitted the invariant mass of the
Be+ and Be++ systems to be reconstructed. In the case of
the breakup of B, a very narrow structure at threshold was observed in
the Be+ channel. Contrary to earlier stable beam fragmentation
studies which identified this as a strongly interacting -wave virtual state
in Be, analysis here of the Be++ events demonstrated that
this was an artifact resulting from the sequential-decay of the
Be(2) state. Single-proton removal from B was found to
populate a broad low-lying structure some 0.70 MeV above the neutron-decay
threshold in addition to a less prominent feature at around 2.4 MeV. Based on
the selectivity of the reaction and a comparison with (0-3)
shell-model calculations, the low-lying structure is concluded to most probably
arise from closely spaced J=1/2 and 5/2 resonances
(E=0.400.03 and 0.85 MeV), whilst the broad
higher-lying feature is a second 5/2 level (E=2.350.14 MeV). Taken
in conjunction with earlier studies, it would appear that the lowest 1/2
and 1/2 levels lie relatively close together below 1 MeV.Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical
Review
Collapse of the N=28 shell closure in Si
The energies of the excited states in very neutron-rich Si and
P have been measured using in-beam -ray spectroscopy from the
fragmentation of secondary beams of S at 39 A.MeV. The low 2
energy of Si, 770(19) keV, together with the level schemes of
P provide evidence for the disappearance of the Z=14 and N=28
spherical shell closures, which is ascribed mainly to the action of
proton-neutron tensor forces. New shell model calculations indicate that
Si is best described as a well deformed oblate rotor.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. let
Emergence of the N=16 shell gap in ^(21)O
This is the publisher's version, also available electronically from http://journals.aps.org/prc/abstract/10.1103/PhysRevC.84.011301
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