Theory of extraordinary transmission of light through quasiperiodic arrays of subwavelength holes

By using a theoretical formalism able to work in both real and k-spaces, the physical origin of the phenomenon of extraordinary transmission of light through quasi-periodic arrays of holes is revealed. Long-range order present in a quasiperiodic array selects the wavevector(s) of the surface electromagnetic mode(s) that allows an efficient transmission of light through subwavelength holes.Comment: 4 pages, 4 figure

Thresholdless Coherent Light Scattering from Subband-polaritons in a Strongly-Coupled Microcavity

We study a "strongly-coupled" (SC) polariton system formed between the atom-like intersubband transitions in a semiconductor nanostructure and the THz optical modes that are localised at the edges of a gold aperture. The polaritons can be excited optically, by incoherent excitation with bandgap radiation, and we find that they also coherently scatter the same input laser, to give strikingly sharp "sideband" (SB) spectral peaks in the backscattered spectrum. The SB intensity is a sensitive track of the polariton density and they can be detected down to a quantum noise floor that is more than 2500 times lower than the excitation thresholds of comparable quantum cascade laser diodes. Compared with other coherent scattering mechanisms, higher order SB scattering events are readily observable, and we speculate that the effect may find utility as a passive all-optical wavelength shifting mechanism in telecommunications systems.Comment: 4 page

Geometrically induced modification of surface plasmons in the optical and telecom regimes

We demonstrate that the introduction of a subwavelength periodic modulation into a metallic structure strongly modifies the guiding characteristics of the surface plasmon modes supported by the system. Moreover, it is also shown how a new type of a tightly confined surface plasmon polariton mode can be created by just milling a periodic corrugation into a metallic ridge placed on top of a metal surface

Influence of culinary process on free and bound (poly)phenolic compounds and antioxidant capacity of artichoke

Artichokes are an important source of (poly)phenolic compounds, mainly caffeoylquinic acids, which consumption has been associated with health benefits. However, heat treatments have shown to affect the amounts of these bioactive food compounds. In the present study the influence of culinary techniques (boiling, griddling, and frying) on the total (poly)phenolic content of artichokes (Cynara Scolymus cv. Blanca de Tudela) was evaluated by LC-MS/MS. Additionally, the antioxidant capacity of cooked artichokes was evaluated by spectrophotometric methods. A total of 31 (poly)phenols were identified and quantified, being caffeoylquinic acids the most abundant compounds in raw artichokes accounting for more than 95% of total (poly)phenolic compounds. With the different culinary techniques, these compounds suffered degradation but also redistribution, probably due to isomerization and hydrolysis reactions. Frying and griddling showed the lowest content of (poly)phenolic compounds and antioxidant capacity suggesting thermal degradation. Boiling also provoked losses, which were mainly due to leaching of phenolic compounds into the water. However, it was the heat treatment that best preserved (poly)phenolic compounds in artichokes

Optical properties of carbon nanofiber photonic crystals

Carbon nanofibers (CNF) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNF were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n_CNF = 4.1.Comment: 10 pages, 4 figure

In vivo study of the bioavailability and metabolic profile of (poly)phenols after sous-vide artichoke consumption

Artichokes are a rich source of (poly)phenols, mainly caffeoylquinic acids, but little is known about their bioavailability from this source. This study investigated the absorption, metabolism and excretion of (poly)phenols after sous-vide artichoke consumption (5776 µmol of (poly)phenols) by healthy volunteers. Seventy-six (poly)phenol metabolites were identified by UHPLC-MS/MS using authentic standards, including acyl-quinic acids plus C6–C3, C6–C1, C6–C2, C6–C1–N, C6–C0 metabolites, and their phase-II conjugates. The major metabolites were 3ʹ-methoxy-4ʹ-hydroxycinnamic acid, 3ʹ-methoxycinnamic acid-4ʹ-sulfate, and 4ʹ-hydroxycinnamic acid-3ʹ-sulfate, which appeared early in plasma (Tmax 6 h). The 24 h urinary recovery averaged 8.9% (molar basis) of the (poly)phenols consumed. Hepatic beta-oxidation of 3ʹ,4ʹ-dihydroxycinnamic acid and methylated conjugates occurred, but was limited (<0.04%). 3ʹ-Methylation exceeded 4ʹ-methylation and interindividual variability was high, especially for gut microbial metabolites (up to 168-fold)

Search for new resonant states in 10C and 11C and their impact on the cosmological lithium problem

The observed primordial 7Li abundance in metal-poor halo stars is found to be lower than its Big-Bang nucleosynthesis (BBN) calculated value by a factor of approximately three. Some recent works suggested the possibility that this discrepancy originates from missing resonant reactions which would destroy the 7Be, parent of 7Li. The most promising candidate resonances which were found include a possibly missed 1- or 2- narrow state around 15 MeV in the compound nucleus 10C formed by 7Be+3He and a state close to 7.8 MeV in the compound nucleus 11C formed by 7Be+4He. In this work, we studied the high excitation energy region of 10C and the low excitation energy region in 11C via the reactions 10B(3He,t)10C and 11B(3He,t)11C, respectively, at the incident energy of 35 MeV. Our results for 10C do not support 7Be+3He as a possible solution for the 7Li problem. Concerning 11C results, the data show no new resonances in the excitation energy region of interest and this excludes 7Be+4He reaction channel as an explanation for the 7Li deficit.Comment: Accepted for publication in Phys. Rev. C (Rapid Communication