Concave Plasmonic Particles: Broad-Band Geometrical Tunability in the Near Infra-Red

Optical resonances spanning the Near and Short Infra-Red spectral regime were exhibited experimentally by arrays of plasmonic nano-particles with concave cross-section. The concavity of the particle was shown to be the key ingredient for enabling the broad band tunability of the resonance frequency, even for particles with dimensional aspect ratios of order unity. The atypical flexibility of setting the resonance wavelength is shown to stem from a unique interplay of local geometry with surface charge distributions

Editorial: Videos in der (Hochschul-)Lehre

24.04.2014 | Thomas Antretter, Johannes Dorfinger, Martin Ebner, Michael Kopp, Walther Nagler, Jutta Pauschenwein, Michael Raunig, Manfred Rechberger, Herwig Rehatschek, Patrick Schweighofer, Reinhard Staber & Martin Teufel (Graz

Numerical Modeling of Plasmonic Nanoantennas with Realistic 3D Roughness and Distortion

Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement factor that should be involved in their design. Herein we aim to treat roughness by introducing a realistic roughened geometry into the finite element (FE) model. Even if the roughness does not result in significant loss, it does result in a spectral shift and inhomogeneous broadening of the resonance, which could be critical when fitting the FE simulations of plasmonic nanoantennas to experiments. Moreover, the proposed approach could be applied to any model, whether mechanical, acoustic, electromagnetic, thermal, etc, in order to simulate a given roughness-generated physical phenomenon

<i>orsai</i>, the Drosophila homolog of human ETFRF1, links lipid catabolism to growth control

BACKGROUND: Lipid homeostasis is an evolutionarily conserved process that is crucial for energy production, storage and consumption. Drosophila larvae feed continuously to achieve the roughly 200-fold increase in size and accumulate sufficient reserves to provide all energy and nutrients necessary for the development of the adult fly. The mechanisms controlling this metabolic program are poorly understood. RESULTS: Herein we identified a highly conserved gene, orsai (osi), as a key player in lipid metabolism in Drosophila. Lack of osi function in the larval fat body, the regulatory hub of lipid homeostasis, reduces lipid reserves and energy output, evidenced by decreased ATP production and increased ROS levels. Metabolic defects due to reduced Orsai (Osi) in time trigger defective food-seeking behavior and lethality. Further, we demonstrate that downregulation of Lipase 3, a fat body-specific lipase involved in lipid catabolism in response to starvation, rescues the reduced lipid droplet size associated with defective orsai. Finally, we show that osi-related phenotypes are rescued through the expression of its human ortholog ETFRF1/LYRm5, known to modulate the entry of β-oxidation products into the electron transport chain; moreover, knocking down electron transport flavoproteins EtfQ0 and walrus/ETFA rescues osi-related phenotypes, further supporting this mode of action. CONCLUSIONS: These findings suggest that Osi may act in concert with the ETF complex to coordinate lipid homeostasis in the fat body in response to stage-specific demands, supporting cellular functions that in turn result in an adaptive behavioral response. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12915-022-01417-w

Practical Electromagnetic Template Attack on HMAC

The original publication is available at www.springerlink.comInternational audienceIn this paper, we show that HMAC can be attacked using a very efficient side channel attack which reveals the Hamming distance of some registers. After a profiling phase which requires access to a similar device that can be configured by the adversary, the attack recovers the secret key on one recorded execution of HMAC-SHA-1 for example, on an embedded device. We perform experimentations using a NIOS processor executed on a Field Programmable Gate Array (FPGA) to confirm the leakage model. Besides the high efficiency of this attack, $2^32\cdot 3^k$ where $k$ is the number of 32-bit words of the key, that we tested with experimentations, our results also shed some light on the on the requirements in term of side channel attack for the future SHA-3 function. Finally, we show that our attack can also be used to break the confidentiality of network protocols usually implemented on embedded devices. We have performed experiments using a NIOS processor executed on a Field Programmable Gate Array (FPGA) to confirm the leakage model. We hope that our results shed some light on the requirements in term of side channel attack for the future SHA-3 function

Mode imaging and selection in strongly coupled nanoantennas

The number of eigenmodes in plasmonic nanostructures increases with complexity due to mode hybridization, raising the need for efficient mode characterization and selection. Here we experimentally demonstrate direct imaging and selective excitation of the bonding and antibonding plasmon mode in symmetric dipole nanoantennas using confocal two-photon photoluminescence mapping. Excitation of a high-quality-factor antibonding resonance manifests itself as a two-lobed pattern instead of the single spot observed for the broad bonding resonance, in accordance with numerical simulations. The two-lobed pattern is observed due to the fact that excitation of the antibonding mode is forbidden for symmetric excitation at the feedgap, while concomitantly the mode energy splitting is large enough to suppress excitation of the bonding mode. The controlled excitation of modes in strongly coupled plasmonic nanostructures is mandatory for efficient sensors, in coherent control as well as for implementing well-defined functionalities in complex plasmonic devices.Comment: 11 pages, 5 figures, 1 supplementary informatio