Search results for " element"

A damping preconditioner for time-harmonic wave equations in fluid and elastic material

2009

A physical damping is considered as a preconditioning technique for acoustic and elastic wave scattering. The earlier preconditioners for the Helmholtz equation are generalized for elastic materials and three-dimensional domains. An algebraic multigrid method is used in approximating the inverse of damped operators. Several numerical experiments demonstrate the behavior of the method in complicated two-dimensional and three-dimensional domains. peerReviewed

On the Finite Element Simulation of Secondary Operations on Metallic Foams

2007

Metallic foams have been recently introduced also as industrial materials due to their well known advantages. In fact, their low mass in conjunction with the good thermal and mechanical properties push toward an extensive diffusion in manufacturing industry. In the study here addressed, a very accurate investigation concerning the latter two aspects has been carried out. In fact, a secondary manufacturing process, i.e. the foam bending, has been taken into account. Anyway, all the knowledge derived for sheet metal bending is not directly applicable to the foams. A finite element code has been utilized for modeling the foam behavior during the bending processes and an accurate material rheol…

Geochemical processes assessed by Rare Earth Elements fractionation at "Laguna Verde" acidic-sulphate crater lake (Azufral volcano, Colombia)

2017

Abstract The geochemical behaviour of major elements, Fe, Al, Mn, and Rare Earth Elements (REE) was investigated in the “Laguna Verde” acidic crater lake of Azufral volcano (Colombia). The cold lake water (T close to 10 °C) is sulphate-dominated, due to absorption and oxidation of H2S (pH 2.1–2.7, Eh 196–260 mV), and Na-enriched (Total Dissolved Solids 0.79 g L−1). The total amount of REE dissolved in the lake ranges from 3.3 to 9.1 ppb. The REE patterns normalized to the local rocks show a Light Rare Earth Elements (LREE) depletion quite constant in the 15 samples. Similar patterns were already found in the acidic sulphate springs of Nevado del Ruiz volcano-hydrothermal system, caused by t…

Selective erasure of a fear memory

2009

International audience; Memories are thought to be encoded by sparsely distributed groups of neurons. However, identifying the precise neurons supporting a given memory (the memory trace) has been a long-standing challenge. We have shown previously that lateral amygdala (LA) neurons with increased cyclic adenosine monophosphate response element-binding protein (CREB) are preferentially activated by fear memory expression, which suggests that they are selectively recruited into the memory trace. We used an inducible diphtheria-toxin strategy to specifically ablate these neurons. Selectively deleting neurons overexpressing CREB (but not a similar portion of random LA neurons) after learning b…

Emerging contributions of formyl peptide receptors to neurodegenerative diseases.

2021

Abstract Inflammation is a central element of many neurodegenerative diseases. Formyl peptide receptors (FPRs) can trigger several receptor-dependent signal transduction pathways that play a key role in neuroinflammation and neurodegeneration. They are chemotactic receptors that help to regulate pro- and anti-inflammatory responses in most mammals. FPRs are primarily expressed in the immune and nervous systems where they interact with a complex pattern of pathogen-derived and host-endogenous molecules. Mounting evidence points towards a contribution of FPRs – via neuropathological ligands such as Amyloid beta, and neuroprotective ligands such as Humanin, Lipoxin A4, and Annexin A1 – to mult…

La Cupola del Teatro Massimo: Il contemporaneo nel 1876

2011

Isotope dilution mass spectrometry as a calibration method for the analysis of trace elements in powder samples by LA-ICP-MS

2003

The applicability of the isotope dilution (ID) technique for trace element determinations in powdered solid samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is demonstrated. LA-ICP-IDMS combines the advantage of the isotope dilution technique as a definitive method with the powerful capability of LA-ICP-MS for a fast and direct multi-element analysis of solid samples. LA-ICP-IDMS therefore allows matrix-matched quantification of element concentrations without any external standard, which is not possible by other calibration strategies used in LA-ICP-MS, up to now. The sample preparation effort is kept minimal and consists of an addition of the corresponding…

Electrochemical pH Control at Gold Nanowires

2018

In this work, interdigitated arrays of nanowire electrodes are used with one array acting as the working electrode while the other is used to generate the required protons. Finite element simulations of the pH control electrodes were performed to provide insight on the generation and subsequent diffusion of protons. This informed the inter-tine spacing of the electrodes used.. This electrochemical pH control method was then used to enable the detection of analytes of interest.

Trace elemental composition of curry by inductively coupled plasma optical emission spectrometry (ICP-OES)

2008

A methodology based on inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave-assisted acid digestion was developed to determine the content of traces elements in curry samples from the Spanish market. The methodology was validated in terms of accuracy by the analysis of citrus and tomato leaf reference materials achieving comparable results with the certified values. The trace metal content of curry samples was compared with data available from previously published reports concerning Indian samples, especially in terms of heavy metal composition, in order to guarantee the quality of the commercially available spices in the European countries. Values found for th…

Spectroscopic Detection and Structure of Hydroxidooxidosulfur (HOSO) Radical, An Important Intermediate in the Chemistry of Sulfur-Bearing Compounds

2013

The rotational spectrum of hydroxidooxidosulfur, HOSO, an intermediate of particular interest in the combustion of sulfur-rich fuels, has been determined to high accuracy from gas-phase measurements. Detection of specific isotopic species using isotopically enriched gases suggests that HOSO is formed in our discharge nozzle via the reaction H + SO2 (+M) → HOSO (+M). A precise experimental r0 geometry has also been derived from the isotopic analysis; HOSO has a cis configuration, but the subtle structural question of its planarity remains unresolved. From the derived spectroscopic constants, in situ and remote sensing for this fundamental radical can now be undertaken in a variety of environ…