Search results for "shell"

Edge-dependent selection rules in magic triangular graphene flakes

2008

The electronic shell and supershell structure of triangular graphene quantum dots has been studied using density functional and tight-binding methods. The density functional calculations demonstrate that the electronic structure close to the Fermi energy is correctly described with a simple tight-binding model, where only the ${p}_{z}$ orbitals perpendicular to the graphene layer are included. The results show that (i) both at the bottom and at the top of the ${p}_{z}$ band, a supershell structure similar to that of free electrons confined in a triangular cavity is seen, (ii) close to the Fermi level, the shell structure is that of free massless particles, (iii) triangles with armchair edge…

Spatiotemporal properties of nanoshell plasmonic response for strong-field experiments

2015

International audience; Field enhancement behavior of a SiO 2 /Au nanoshell is studied in the framework of strong-field physics. Localized plasmonic fields induce local electric field enhancement with the potential to lead to the strong-field regime without the use of costly amplified lasers. In this framework, electrons are tunnel ionized from the nanoshell and accelerated by the local field being spatially inhomogeneous in terms of spectral and polarization properties. These processes are happening within a single laser shot, and thermal effects are therefore neglected. We show that the localized response to ultrashort femtosecond pulses can be investigated by extending Mie theory to mult…

Metamodeling editor as a front end tool for a CASE shell

1992

Customizable Computer Aided Software Engineering (CASE) tools, often called CASE shells, are penetrating in the market. CASE shells provide a flexible environment to support a variety of information systems development methods. CASE shells are often cumbersome to use and in practice few people can model and implement methods in them. To overcome these problems we have developed a graphical metamodeling environment called MetaEdit and a method modeling interface to the CASE shell RAMATIC. Using this interface the methodology engineer can develop graphical models in RAMATIC's model definition language and then easily generate the resource files that control the operations of RAMATIC. MetaEdit…

Front Cover: Valorisation of Cashew Nut Shell Liquid Phenolics in the Synthesis of UV Absorbers (Eur. J. Org. Chem. 30/2019)

2019

Comparative Study for Springback Prediction on Single Point Incremental Forming Process

2014

The present paper proposes a comparative study in order to determine the springback in single point incremental forming process. Using the Ls-Dyna software the process was simulated for one piece in frustum of pyramid shape. In the end of the explicit dynamic analysis, it was run, using the same software, an implicit analysis to determine the springback. For this comparison study we selected four different shell formulations. The results obtained in this simulation were compared with those obtained experimentally for the same part. The experimental research was conducted on a robot and, on the opposite side of the machined surface, an Aramis measuring optical system was placed to allow the …

Influence of a density mismatch on TMPTMA shells nonconcentricity

2011

Some laser target designs require low-density organic foam shells to study fusion on the French high-power laser laser mega joule. Low-density trimethylolpropane trimethacrylate foam shells composed of C, H, and O, 2 mm diameter, 100-μm wall thickness, and 250 mg cm−3 density are synthesized by a microencapsulation technique using a droplet generator. These shells have to reach a sphericity higher than 99.9% and a nonconcentricity (NC) lower than 1%. The wall thickness variation is one of the most difficult specifications to meet. An important factor in reducing this defect is the density matching between the three phases of the emulsion at polymerization temperature. The influence of a den…

GIV noroviruses and other enteric viruses in bivalves: a preliminary study.

2012

We evaluated the presence of the enteric viruses: norovirus, adenovirus, enterovirus, astrovirus, hepatitis A virus, and hepatitis E virus in bivalves using nested PCR methods and cell culture assays. Noroviruses GII.4 and GIV.1, adenoviruses types 1 and 2, hepatitis A, and echovirus type 7 were detected in the shellfish tested, which were often co-infected. This is the first study to detect such a high level of viral contamination in Italian mussels (up to four different viral groups in a single sample), and the first to document the presence of GIV NoV in shellfish.

55-Atom clusters of silver and gold: Symmetry breaking by relativistic effects

2006

Abstract Anionic 55-atom clusters of gold and silver are studied using density functional theory, scalar relativistic ab initio pseudopotentials and self-consistent generalized gradient corrections. An almost perfect icosahedron is found to be the clear ground state of Ag 55 - , and its electronic density of states agrees almost perfectly with recently measured high-resolution photoelectron spectra, up to the magnitude of the splitting of the highest free-electron shells by the Ih crystal field. A comparison between theory and a recent experiment allows one to assign icosahedral-based structures also for the Ag 57 - cluster. On the other hand, the Au 55 - cluster has several close-lying low…

The formation and mineralization of mollusk shell.

2011

27 pages; International audience; In the last years, the field of mollusk biomineralization has known a tremendous mutation. The most recent advances deal with the nanostructure of shell biominerals, and with the identification of several shell matrix proteins: on one hand, the complex hierarchical organization of shell biominerals has been deciphered in few models, like nacre. On the other hand, although proteins represent a minor shell component, they are the major macromolecules that control biocrystal synthesis. Until recently, the paradigm was to consider that this control occurs by two antagonist mechanisms: crystal nucleation and growth inhibition. Emerging models try to translate a …

Potential and limitation of combining terrestrial and marine growth records from Iceland

2017

Abstract Seasonally formed, perennial growth increments of various organisms may possibly contain information about past environmental changes, well before instrumental measurements occurred. Such annually resolved proxy records have been mainly obtained from terrestrial archives, with a paucity of similar data originating from marine habitats. Iceland represents ideal conditions to develop both, tree ring (dendro) and bivalve shell (sclero) chronologies from adjacent sites. Here we introduce the first network of Icelandic birch (Betula pubescens Ehrh.) and rowan (Sorbus aucuparia) dendrochronologies, as well as ocean quahog (Arctica islandica L.) sclerochronologies. In order to identify th…