Search results for "ABLATION"

Referenceless thermometry using radial basis function interpolation

2014

The Proton Resonance Frequency (PRF) shift provide a method for temperature change measurements during thermotherapy. Conventional PRF thermometry works subtracting one or multiple baseline images. The method leads to artifacts caused by tissue motion and frequency drift. Various works estimating the background phase from each acquired image phase are present in literature. These algorithms are called “referenceless” because they don’t require any subtraction of baseline images for calculating temperature increment. Conventional referenceless methods estimate baseline image by fitting the background phase outside the heated region through a polynomial approach. In this work a background pha…

Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?

2019

The geological roots of South America: 4.1 Ga and 3.7 Ga zircon crystals discovered in N.E. Brazil and N.W. Argentina

2015

International audience; We present new LA-ICP-MS in situ geochronological results for seven Eoarchean zircons dated at 3.7 Ga coming from Cretaceous ash layers of NW Argentina and one Hadean single crystal sampled within the São Francisco Craton in NE Brazil. This zircon comprises a zoned magmatic core dated at 4.1 Ga surrounded by a 1.9 Ga overgrowth related to Paleoproterozoic reworking. This Hadean age is consistent with previously published Nd model ages on orthogneisses from the same domain. These two results represent among the oldest geological witnesses discovered to date in South America, which demonstrates the occurrence of a primitive crust. The contrasting age patterns recorded …

Atrial Fibrosis Hampers Non-invasive Localization of Atrial Ectopic Foci From Multi-Electrode Signals: A 3D Simulation Study

2018

[EN] Introduction: Focal atrial tachycardia is commonly treated by radio frequency ablation with an acceptable long-term success. Although the location of ectopic foci tends to appear in specific hot-spots, they can be located virtually in any atrial region. Multi-electrode surface ECG systems allow acquiring dense body surface potential maps (BSPM) for non-invasive therapy planning of cardiac arrhythmia. However, the activation of the atria could be affected by fibrosis and therefore biomarkers based on BSPM need to take these effects into account. We aim to analyze the effect of fibrosis on a BSPM derived index, and its potential application to predict the location of ectopic foci in the …

Sr-isotope analysis of speleothems by LA-MC-ICP-MS: High temporal resolution and fast data acquisition

2017

Speleothems are well established climate archives. A wide array of geochemical proxies, including stable isotopes and trace elements are present within speleothems to reconstruct past climate variability. However, each proxy is influenced by multiple factors, often hampering robust interpretation. Sr isotope ratios (87Sr/86Sr) can provide useful information about water residence time and water mixing in the host rock, as they are not fractionated during calcite precipitation. Laser ablation multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has rarely been used for determination of Sr isotope signatures in speleothems, as speleothems often do not possess appropriate…

Short term adaptive response of symbiotic N2 fixation in pea to root pruning of half the root system, linked to the availability of carbon assimilates

2014

Symbiotic N fixation of legumes is very sensitive to environmental stresses, like pea pests damaging nodulated roots. However, the impact on their N uptake capacity and plant growth has not been studied so far.We analyzed the adaptive response symbiotic N2 fixation and plant growth of pea wild type Frisson and hypernodulating mutants P64, P118 and P121 mutated respectively on genes SYM28, SYM29 and NOD3 to root pruning of half the root system at the end of the vegetative stage. The adaptive responses of pea: cv. Frisson and 3 of its hypernodulating mutants were compared under varying carbon supplies from photosynthesis.At 380 ppm, mutant P118 showed the lowest decrease of the specific activ…

Targets on superhydrophobic surfaces for laser ablation ion sources

2012

Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser…

Development of a carbon-cluster ion source for JYFLTRAP

2008

Abstract A carbon-cluster ion source based on laser ablation and ionization of a carbon sample has been built and tested for the JYFLTRAP setup. In the present configuration the ion source is situated in the electrostatic switchyard in front of the radiofrequency (RFQ) cooler and buncher. In this position the beam quality of the carbon clusters injected into the Penning trap system is considerably improved by the RFQ. Moreover, the mass-dependence of the RFQ’s transmission can be used to some extent to suppress unwanted cluster sizes.

Characterization of laser ablation of copper in the irradiance regime of laser-induced breakdown spectroscopy analysis

2014

Abstract The LIBS signal depends both on the ablated mass and on the plasma excitation temperature. These fundamental parameters depend in a complex manner on laser ablation and on laser–plasma coupling. As several works in the literature suggest that laser ablation processes play a predominant role compared to plasma heating phenomena in the LIBS signal variations, this paper focuses on the study of laser ablation. The objective was to determine an interaction regime enabling to maximally control the laser ablation. Nanosecond laser ablation of copper at 266 nm was characterized by scanning electron microscopy and optical profilometry analysis, in air at 1 bar and in the vacuum. The laser …

Re-interpreting complex atrial tachycardia maps using global atrial vectors.

2021

Activation maps of scar-related atrial tachycardias (AT) can be challenging to interpret due to difficulty in inaccurate annotation of electrograms, and an arbitrarily predefined mapping window. A novel mapping software integrating vector data and applying an algorithmic solution taking into consideration global activation pattern has been recently described (Coherent™, Biosense Webster "Investigational").We aimed to assess the investigational algorithm to determine the mechanism of AT compared with the standard algorithm.This study included patients who underwent ablation of scar-related AT using the Carto 3 and the standard activation algorithm. The mapping data were analyzed retrospectiv…