3,089 research outputs found
Faraday effect in rippled graphene: Magneto-optics and random gauge fields
A beam of linearly polarized light transmitted through magnetically biased
graphene can have its axis of polarization rotated by several degrees after
passing the graphene sheet. This large Faraday effect is due to the action of
the magnetic field on graphene's charge carriers. As deformations of the
graphene membrane result in pseudomagnetic fields acting on the charge
carriers, the effect of random mesoscopic corrugations (ripples) can be
described as the exposure of graphene to a random pseudomagnetic field. We aim
to clarify the interplay of these typically sample inherent fields with the
external magnetic bias field and the resulting effect on the Faraday rotation.
In principle, random gauge disorder can be identified from a combination of
Faraday angle and optical spectroscopy measurements.Comment: 7 pages, 4 figure
Heat production and energy balance in nanoengines driven by time-dependent fields
We present a formalism to study the heat transport and the power developed by
the local driving fields on a quantum system coupled to macroscopic reservoirs.
We show that, quite generally, two important mechanisms can take place: (i)
directed heat transport between reservoirs induced by the ac potentials and
(ii) at slow driving, two oscillating out of phase forces perform work against
each other, while the energy dissipated into the reservoirs is negligibleComment: 5 pages, 4 figure
Tunable plasmon-enhanced birefringence in ribbon array of anisotropic 2D materials
We explore the far-field scattering properties of anisotropic 2D materials in
ribbon array configuration. Our study reveals the plasmon-enhanced linear
birefringence in these ultrathin metasurfaces, where linearly polarized
incident light can be scattered into its orthogonal polarization or be
converted into circular polarized light. We found wide modulation in both
amplitude and phase of the scattered light via tuning the operating frequency
or material's anisotropy and develop models to explain the observed scattering
behavior
Anisotropic Acoustic Plasmons in Black Phosphorus
Recently, it was demonstrated that a graphene/dielectric/metal configuration
can support acoustic plasmons, which exhibit extreme plasmon confinement an
order of magnitude higher than that of conventional graphene plasmons. Here, we
investigate acoustic plasmons supported in a monolayer and multilayers of black
phosphorus (BP) placed just a few nanometers above a conducting plate. In the
presence of a conducting plate, the acoustic plasmon dispersion for the
armchair direction is found to exhibit the characteristic linear scaling in the
mid- and far-infrared regime while it largely deviates from that in the long
wavelength limit and near-infrared regime. For the zigzag direction, such
scaling behavior is not evident due to relatively tighter plasmon confinement.
Further, we demonstrate a new design for an acoustic plasmon resonator that
exhibits higher plasmon confinement and resonance efficiency than BP ribbon
resonators in the mid-infrared and longer wavelength regime. Theoretical
framework and new resonator design studied here provide a practical route
toward the experimental verification of the acoustic plasmons in BP and open up
the possibility to develop novel plasmonic and optoelectronic devices that can
leverage its strong in-plane anisotropy and thickness-dependent band gap
Wildfire spreading simulator using fast marching algorithm
Programs that can predict wildfire behavior are a very useful tool in terms of extinguishing these fires more effectively. State of the art wildfire simulators present some drawbacks such as not being sufficiently user-friendly, being expensive, requiring great computational power or having poor graphical representation. This paper presents a prototype wildfire simulation app that uses Fast Marching (FM) as its core algorithm. The wildfire app is developed as a Matlab GUI. Said application shows the shape of the fire front at a given moment in time in a 3D map of the terrain affected by the fire. Any real life maps can be loaded to the application for wildfire prediction. The user can choose to vary parameters such as starting (ignition) and ending points, wind direction and speed and propagation time, and see its effect on fire propagation. Interface response to each change in the input is very fast, therefore proving the effciency of the algorithm. Although a prototype, the wildfire basic app is superior to some state of the art simulators regarding certain important features. It can be concluded that Fast Marching is a valid core algorithm for a fire simulator. The way the app is programmed in Matlab confers it flexibility, enabling further specific changes that make it truly competitive against currently used wildfire simulators
Switching the Symmetry of Graphene Plasmons with Nanoemitters for Ultimate Infrared-Light Confinement
Vertical plasmonic coupling in double-layer graphene leads to two hybridized plasmonic modes: the optical and the acoustic plasmon with symmetric and antisymmetric charge distributions across the interlayer gap, respectively. However, in most experiments based on far-field excitation, only the optical plasmon are dominantly excited in the double-layer graphene systems. Here, we propose strategies to selectively and efficiently excite the acoustic plasmon with single or multiple nanoemitters. The analytical model developed here elucidates the role of the position and arrangement of the emitters on the symmetry of the resulting graphene plasmons. In addition, we present an optimal device structure to enable an experimental observation of the acoustic plasmon in double-layer graphene toward the ultimate level of plasmonic confinement defined by a monoatomic spacer, which is inaccessible with a graphene-on-a-mirror architecture
Laser shock processing as a method of decreasing fatigue of a die-casting die made of maraging steel
Laser Shock Processing (LSP) is a process of laser treatment with a pulsed beam of high-power density. The process generates locally limited mechanical waves that increase the through-depth density of dislocations. This entails a change in mechanical properties, particularly at the workpiece surface. The treatment with laser-induced shock waves is suitable for structural parts and machine elements subjected to high thermo-dynamical loads. LSP can substantially improve the wear resistance, which is of exceptional significance to die-casting tools made of maraging steel. The paper describes the effects of LSP on chosen 12% Ni maraging steel, which is suitable also for the manufacture of tools for die casting of aluminium alloys. After laser treatment, measurements of residual stresses and microhardness and other properties, including surface defects at the micro level, were carried out. The results of the study confirmed that exceptionally favourable residual stresses and microhardness could be obtained
Shaping substrate selectivity in a broad-spectrum metallo-β-lactamase
Metallo-β-lactamases (MBLs) are the major group of carbapenemases produced by bacterial pathogens. The design of MBL inhibitors has been limited by, among other issues, incomplete knowledge about how these enzymes modulate substrate recognition. While most MBLs are broad-spectrum enzymes, B2 MBLs are exclusive carbapenemases. This narrower substrate profile has been attributed to a sequence insertion present in B2 enzymes that limits accessibility to the active site. In this work, we evaluate the role of sequence insertions naturally occurring in the B2 enzyme Sfh-I and in the broad-spectrum B1 enzyme SPM-1. We engineered a chimeric protein in which the sequence insertion of SPM-1 was replaced by the one present in Sfh-I. The chimeric variant is a selective cephalosporinase, revealing that the substrate profile of MBLs can be further tuned depending on the protein context. These results also show that the stable scaffold of MBLs allows a modular engineering much richer than the one observed in nature.Fil: González, Lisandro J.. Instituto de Biologia Molecular y Celular de Rosario; ArgentinaFil: Stival, Cintia Estefanía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Puzzolo, Juan Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Moreno, Diego M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Aguilar Vila, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin
Log of the inverse of the distance transform and fast marching applied to path planning
Abstract-This paper presents a new Path Planning method based in the inverse of the Logarithm of the Distance Transform and in the Fast Marching Method. The Distance Transform of an image gives a grey scale that is darker near the obstacles and walls and more clear far from them and it is calculated via Voronoi Diagram. The Logarithm of the inverse of the Distance Transform imitates the repulsive electric potential from walls and obstacles. This method is very fast and reliable and the trajectories are similar to the human trajectories: smooth and not very close to obstacles and walls
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