Channel plasmon-polaritons: modal shape, dispersion, and losses

We theoretically study channel plasmon-polaritons (CPPs) with a geometry similar to that in recent experiments at telecom wavelengths (Bozhevolnyi et al., Nature 440, 508 (2006)). The CPP modal shape, dispersion relation, and losses are simulated using the multiple multipole method and the finite difference time domain technique. It is shown that, with the increase of the wavelength, the fundamental CPP mode shifts progressively towards the groove opening, ceasing to be guided at the groove bottom and becoming hybridized with wedge plasmon-polaritons running along the groove edges.Comment: 4 pages, 4 figure

Theory of Negative-Refractive-Index Response of Double-Fishnet Structures

A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light

(Z)-N-(2-Iodophenyl)-4-nitrobenzimidoyl cyanide

In the title molecule, C14H8IN3O2, the cyanide group is anti to the iodide substituent of the adjacent benzene ring. The central segment is essentially planar (r.m.s deviation = 0.0341 A ° ) and it is twisted away from the iodide- and nitro-substituted benzene rings by 69.02 (9) and 15.83 (16), respectively. In the crystal, molecules are linked by weak C—H N interactions, leading to C(8) chains along [010]

Paleoenvironmental evolution of Laguna Seca lake (Sierra Nevada, southern Iberia) since the Late Glacial

Comunicación oral en XXI INQUA Congress. Rome (Italy). 14-20th july 2023Laguna Seca lake at 2259 masl has provided the longest alpine sedimentary record in southern Iberia, registering the last ~18 kyr in a ~14-meter-long sediment core. The oldest part of the sedimentary record represents a phase of subaerial debris flows and a small glacier/nivation hollow. The sediment characteristics abruptly changed at ~15.7 cal kyr BP, when a lake environment was established. A multi-proxy approach (magnetic susceptibility, organic geochemical analyses in bulk sediment, XRF core scanner data, and algae identification) has allowed the characterization of three different environmental phases in this lake. Deep lake conditions are identified from ~15.7 to ~10.6 cal kyr BP, agreeing with overall increasing precipitation in southern Iberia coinciding with augmenting summer insolation. This part of the record is characterized by grey lutites with high total organic carbon (TOC) content, high algae productivity, high vascular plant inputs (high C/N ratio) from the catchment and low Fe/S ratio, suggesting low oxygen conditions in the water-sediment interphase. Between ~10.6 and 8.2-8.0 cal kyr BP higher TOC and low Fe/S ratio are also recorded as well as higher algae content and low C/N ratio suggesting high aquatic production and more algae contribution to the local organic matter pool. This period registered the highest lake levels agreeing with summer insolation maximum and highest precipitation in southern Iberia. An abrupt lowering of the lake level is recorded after 8.0 cal kyr BP in the area. This is deduced by the decrease in TOC and algae in the sediments and more siliciclastic contribution from the catchment basin, evidenced by a high increase in siliciclastic elements (Si, Al, K, Ti, among others), with increased oxic conditions in the water-sediment interphase pointed out by the high increase in Fe/S ratio. Additionally, a potential increase in north African aeolian inputs (rich in Fe cations and Fe compounds) can be interpreted for the Middle and Late Holocene, evidenced by high Fe/Al values. This environmental change agrees with an aridification trend previously observed in the southern Iberian Peninsula

Summer temperatures during the Holocene inferred from a chironomid record from Sierra Nevada, southern Spain

XXI INQUA 2023. Rome. july 14-20 2023Accurate and continuous quantitative paleotemperature records from the past are rare in southern Iberia, mostly due to the scarcity of continuous sedimentary sequences in terrestrial environments from that area. In this study we show the first Holocene mean July air temperature reconstruction based on fossil chironomids from a sedimentary sequence obtained from Laguna de Río Seco, an alpine lake in Sierra Nevada, southern Spain. Reconstructed summer temperatures agree with changes in summer insolation and other palaeotemperature records from alpine environments from southern Europe and show the Holocene thermal maximum between 10 to 8.0 ka (1 ka = 1000 cal yr BP). Rapid cooling occurred after the warmest maximum and between ~8.0-7.0 ka and temperatures stabilized between ~6.5 and 3.0 ka. A further cooling trend started ~3.0 ka, and coldest summer conditions were reached at 1.4 ka (~550 CE) and ~0.2 ka (~1750 CE), coinciding with the Dark Ages and Little Ice Age, respectively. This record also shows relatively warmer summer temperature conditions during the Iberian-Roman Humid Period ~2.0 ka and during the Medieval Climate Anomaly at ~0.9 ka. Summer climate warming of more than two degree Celsius is observed in the last decades showing that recent warming is amplified in high alpine environments