A strategy for self-adjointness of Dirac operators: Applications to the MIT bag model and delta-shell interactions

We develop an approach to prove self-adjointness of Dirac operators with boundary or transmission conditions at a $C^2$-compact surface without boundary. To do so we are lead to study the layer potential induced by the Dirac system as well as to define traces in a weak sense for functions in the appropriate Sobolev space. Finally, we introduce Calderón projectors associated with the problem and illustrate the method in two special cases: the well-known MIT bag model and an electrostatic $\delta$-shell interaction.ANR-11- LABX-0056-LMH, LabEx LM

GPGPU computation and visualization of three-dimensional cellular automata

This paper presents a general-purpose simulation approach integrating a set of technological developments and algorithmic methods in cellular automata (CA) domain. The approach provides a general-purpose computing on graphics processor units (GPGPU) implementation for computing and multiple rendering of any direct-neighbor three-dimensional (3D) CA. The major contributions of this paper are: the CA processing and the visualization of large 3D matrices computed in real time; the proposal of an original method to encode and transmit large CA functions to the graphics processor units in real time; and clarification of the notion of top-down and bottom-up approaches to CA that non-CA experts often confuse. Additionally a practical technique to simplify the finding of CA functions is implemented using a 3D symmetric configuration on an interactive user interface with simultaneous inside and surface visualizations. The interactive user interface allows for testing the system with different project ideas and serves as a test bed for performance evaluation. To illustrate the flexibility of the proposed method, visual outputs from diverse areas are demonstrated. Computational performance data are also provided to demonstrate the method’s efficiency. Results indicate that when large matrices are processed, computations using GPU are two to three hundred times faster than the identical algorithms using CPU

Honey, a Gift from Nature to Health and Beauty: A Review

Benefits of honey are contributed by the composition of its elements such as glucose, fructose, glucose oxidase, vitamins and phenolic compounds. For health, honey can be used to treat wounds due to the antibacterial activity conferred by the hydrogen peroxide produced by glucose oxidase in honey. Anti-inflammatory, anti-oxidant, deodorizing and tissue regeneration activities in honey also help in the wound healing process. It can also be an alternative sweetener for diabetic patients to ensure compliance to a healthy diet. Moreover, honey exerts several effects such as lowering low density lipids and increasing high density lipids, thus reducing risk of atherosclerosis. In terms of beauty, honey can be used on skin and hair. It moisturizes skin through its natural humectant properties contributed by high contents of fructose and glucose. Honey treats acne on the skin due to its antibacterial activity, anti-inflammatory action and tissue repair. The hair can benefit from honey in such a way that the hair has abundance, and becomes easier to comb. However, there have not been as many studies regarding the use of honey in skin in comparison to its use for health. Therefore, future studies on honey could research its use, action and benefits in both cosmetics and dermatology

Auger quenching-based modulation of electroluminescence from ion-implanted silicon nanocrystals

We describe high-speed control of light from silicon nanocrystals under electrical excitation. The nanocrystals are fabricated by the ion implantation of Si+ in the 15?nm thick gate oxide of a field effect transistor at 6.5?keV. A characteristic read-peaked electroluminescence is obtained either by DC or AC gate excitation. However, AC gate excitation is found to have a frequency response that is limited by the radiative lifetimes of silicon nanocrystals, which makes impossible the direct modulation of light beyond 100?kb?s?1 rates. As a solution, we demonstrate that combined DC gate excitation along with an AC channel hot electron injection of electrons into the nanocrystals may be used to obtain a 100% deep modulation at rates of 200?Mb?s?1 and low modulating voltages. This approach may find applications in biological sensing integrated into CMOS, single-photon emitters or direct encoding of information into light from Si-nc doped with erbium systems, which exhibit net optical gain. In this respect, the main advantage compared to conventional electro-optical modulators based on plasma dispersion effects is the low power consumption (104 times smaller) and thus the inherent large scale of integration. A detailed electrical characterization is also given. An Si/SiO2 barrier change from ?b = 3.2 to 4.2?eV is found while the injection mechanism is changed from Fowler?Nordheim to channel hot electron, which is a clear signature of nanocrystal charging and subsequent electroluminescence quenching

Hyposensitivity to the amnesic effects of scopolamine or amyloid beta25-35 peptide in heterozygous acetylcholinesterase knockout (AchE+/-) mice

International audienceAcetylcholinesterase (AChE) is the main catabolic enzyme of acetylcholine, responsible for the synaptic clearance of the neurotransmitter from the synaptic cleft. Decrease in AChE expression, or activity, results in increased cholinergic tonus in the brain or periphery, with concomittant regulations of nicotinic and muscarinic receptors expression. We generated AChE knockout mice and characterized the behavioral phenotype of heterozygous animals, particularly focusing on learning and memory functions. Male and female, AChE+/- and AChE+/+ littermate controls (129sv strain), tested at 5-9 weeks of age, failed to show any difference in terms of locomotion, exploration and anxiety parameters in the open-field test. Animals were then tested for place learning in the water-maze. They were trained using a 'sustained acquisition' protocol (3 swims/day during 5 days) or a 'mild acquisition' protocol (2 swims/day during 9 days) to locate an invisible platform in fixed position (reference memory procedure). Then, during 3 days, they were trained to locate the platform in a variable position (working memory procedure). Learning profiles and probe test performances were unchanged in AChE+/- mice as compared with AChE+/+. Mice were then treated with the muscarinic M1 antagonist scopolamine (0.5, 5 mg/kg sc) 20 min before each training session (3 swims/day during 5 days). Scopolamine impaired learning at both doses in AChE+/+ mice, but only at the highest dose in AChE+/- mice. Moreover, the central injection of amyloid beta25-35 peptide (9 nmol) failed to induce learning deficits in AChE+/- mice, contrarily to AChE+/+ controls. These behavioral study shows that the increase in cholinergic tonus did not result in increased memory abilities in these heterozygous AChE+/- mice, but allowed a significant prevention of the deleterious effects of muscarinic blockade or amyloid toxicity

Variation of end of range defects density with ion beam energy and dose: Experiments and simulations

When the amorphous layer created by ion implantation becomes very thin, the density of End Of Range defects (EOR), formed after annealing, decreases. Some investigations [1] have attributed this fact to the motion, by glide or climb, of EOR defects towards the surface. To shed light on this point, many Ge$^{+}$ implantations were carried out at different energies and doses, and very thin layers were elaborated. Based on XTEM observations correlated to “Excess Interstitials model”, we show clearly that the observed phenomenon, can be rigorously explained through collisional arguments in the whole bottom of the crystal. When the beam energy or dose are lowered, the amorphous layer becomes thinner. So, the number of excess interstitials left beneath the c/a interface, which will cluster to form EOR defects, decreases. On the other hand, when EOR defects are formed at the surface's proximity (depth less than 75nm), they act as a sink of Si atoms and lead to a more pronounced reduction of super saturation, which will form EOR defects. However, no EOR defects are observed when the number of excess interstitials becomes less than a minimum threshold, which depends on the depth of these defects

Silicon nanoclusters embedded into oxide host for non-volatile memory applications

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Ag doped silicon nitride nanocomposites for embedded plasmonics

International audienceThe localized surface plasmon-polariton resonance (LSPR) of noble metal nanoparticles (NPs) is widely exploited for enhanced optical spectroscopies of molecules, nonlinear optics, photothermal therapy, photovoltaics, or more recently in plasmoelectronics and photocatalysis. The LSPR frequency depends not only of the noble metal NP material, shape, and size but also of its environment, i.e., of the embedding matrix. In this paper, Ag-NPs have been fabricated by low energy ion beam synthesis in silicon nitride (SiNx) matrices. By coupling the high refractive index of SiNx to the relevant choice of dielectric thickness in a SiNx/Si bilayer for an optimum antireflective effect, a very sharp plasmonic optical interference is obtained in mid-range of the visible spectrum (2.6 eV). The diffusion barrier property of the host SiNx matrix allows for the introduction of a high amount of Ag and the formation of a high density of Ag-NPs that nucleate during the implantation process. Under specific implantation conditions, in-plane self-organization effects are obtained in this matrix that could be the result of a metastable coarsening regime