Search results for " shell"
showing 10 items of 307 documents
A study of noise transmission through cylindrical shell using modal truncation approach
2011
International audience; The study of the vibroacoustic behaviour of cylindrical structure like aircraft fuselage requires the establishment of very large models, and the numerical results which can be obtained are often difficult to interpret. On the other hand, the study of simple structures such as cylindrical shells is useful to validate the criteria and tools that can be used to simplify the models of complex structures. The presented study concerns the sound transmission through a cylindrical shell coupled to a cavity and subjected to an incident acoustic wave. Noise reduction is obtained and validated by a numerical method which uses structural and acoustical modes. A criterion for se…
Trace elemental alterations of bivalve shells following transgenerational exposure to ocean acidification: Implications for geographical traceability…
2020
Trace elements of bivalve shells can potentially record the physical and chemical properties of the ambient seawater during shell formation, thereby providing valuable information on environmental conditions and provenance of the bivalves. In an acidifying ocean, whether and how seawater acidification affects the trace elemental composition of bivalve shells is largely unknown. Here, we investigated the transgenerational effects of OA projected for the end of the 21st century on the incorporation of trace elements into shells of the Manila clam, Ruditapes philippinarum. Neither seawater pH nor transgenerational exposure affected the Mg and Sr composition of the shells. Compared with clams g…
Evaluation of the optimal activation parameters for almond shell bio-char production for capacitive deionization
2020
Abstract A study on a possible new biomass waste to be used as electrode material for capacitive deionization (CDI) processes was performed. Raw almond shells were pyrolyzed at 800, 900 and 1000 °C and then activated through CO2. Carbon activation is used to develop porosity inside the material, increasing the specific surface area and the adsorption performances. In this work, authors tried to correlate the effects of pyrolysis and activation temperature on the ion storage capacity. Results from the desalination tests indicated that the best performance in terms of ion adsorption was obtained when the bio-char was activated at the temperature of 900 °C. Brunauer-Emmet-Teller (BET) and Barr…
Inner-shell excitation spectroscopy of closo-carboranes
1997
Oscillator strength spectra in the region of B 1s and C 1s excitation of three isomeric carborane cage compounds [closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C2B10H...
Interstitial defects in diamond: A quantum mechanical simulation of their EPR constants and vibrational spectra
2020
The local geometry, electronic structure, and vibrational features of three vicinal double interstitial defects in diamond, ICIC, ICIN, and ININ, are investigated and compared with those of three "simple" ⟨100⟩ interstitial defects, ICC, ICN, and INN, previously reported by Salustro et al. [Phys. Chem. Chem. Phys. 20, 16615 (2018)], using a similar quantum mechanical approach based on the B3LYP functional constructed from Gaussian-type basis sets, within a supercell scheme, as implemented in the CRYSTAL code. For the first time, the Fermi contact term and hyperfine coupling tensor B of the four open shell structures, ICIC, ICIN, ICC, and ICN, are evaluated and compared with the available ex…
CFD prediction of shell-side flow and mass transfer in regular fiber arrays
2021
Numerical simulations were conducted for fully developed, steady-state flow with mass transfer in fiber bundles arranged in regular lattices. The porosity was 0.5 and the Schmidt number 500. Several combinations of axial flow, transverse flow and flow attack angles in the cross-section plane were considered. The axial and transverse Reynolds numbers Rez , ReT were made to vary from 10(^−4) to 10(^2). Concentration boundary conditions, and the definition of an average Sherwood number, were addressed. Results for the hydraulic permeability were compared with the literature. Both hexagonal and square lattices were found to be hydraulically almost isotropic up to transverse flow Reynolds number…
The mechanism of formamide hydrolysis in water from ab initio calculations and simulations.
2005
The neutral hydrolysis of formamide in water is a suitable reference to quantify the efficiency of proteolytic enzymes. However, experimental data for this reaction has only very recently been obtained and the kinetic constant determined experimentally is significantly higher than that predicted by previous theoretical estimations. In this work, we have investigated in detail the possible mechanisms of this reaction. Several solvent models have been considered that represent a considerable improvement on those used in previous studies. Density functional and ab initio calculations have been carried out on a system which explicitly includes the first solvation shell of the formamide molecule…
Analysis of the Electronic Structure of Non-Spherical Ligand-Protected Metal Nanoclusters: The Case of a Box-Like Ag67
2016
In this work we introduce a new strategy to investigate the electronic shell structure of ligand-protected metal nanoclusters of polyhedral core shape. The central idea is to identify the symmetry of the Kohn–Sham molecular orbitals of an atomistic structure based on their projection onto the electronic states of a jellium system with a similar shape of the background charge density. Herein, we study the connection between a reduced atomistic model of the recently reported box-like [Ag67(SR)32(PR3)8]3+ nanocluster and a jellium box consisting of 32 free electrons. With this approach, we determine the symmetry of electronic states of the metal core and identify those that are involved in the…
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…