Search results for " abl"
showing 10 items of 296 documents
Bimodal velocity distribution of atoms released from nanosecond ultraviolet laser ablation
2005
We have investigated the velocity distributions of atoms released from a metallic gadolinium surface by UV laser ablation. The fluences of the nanosecond laser pulses were chosen for a pure release of neutrals and at a higher fluence level for the release of both neutrals and ions. In both cases a thermal Maxwell-Boltzmann slope has been observed for the low velocities, whereas for high velocities strong deviations from a thermal distribution have been seen. The observed velocity distribution has been explained by a bimodal structure including a thermal phase and a shockwave driven ``blow-off'' phase.
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 …
Surface modifications induced by nanosecond pulsed Nd:YAG laser irradiation of metallic substrates
2006
International audience; Substrate surface preparation is a key step in coating deposition process. In recent years, pulsed laser cleaning has emerged as a possible technique to challenge the traditional preparation methods (based on degreasing and eventually grit-blasting). The laser operated at short-pulse mode offers high cleaning efficiency and therefore has been largely used. In a specific process named PROTAL®, a nanosecond pulsed laser is introduced to prepare the surface simultaneously to thermal spraying, with the purpose of eliminating the contaminants and generating favorite surface conditions for coating deposition. This study aims at clarifying some fundamental aspects of nanose…
Resistive switching behaviour in ZnO and VO 2 memristors grown by pulsed laser deposition
2014
The resistive switching behaviour observed in microscale memristors based on laser ablated ZnO and VO 2 is reported. A comparison between the two materials is reported against an active device size. The results show that devices up to 300 × 300 μm 2 exhibit a memristive behaviour regardless of the device size, and 100 × 100 μm 2 ZnO-based memristors have the best resistance off/on ratio.
Application of sol-gel and laser evaporation methods to obtain thin gas sensitive films
2005
New type resistive/capacitative gas sensitive structures were obtained by using a specially prepared substrate- glass, covered by thin conducting In/sub 2/O/sub 3/ layer, cutted into a comb teeth-type electrodes by help of laser beam. Such laser processed gap in the layer of conducting material was a prototype of excellent humidity sensor, especially at high values of relative humidity (RH). Different additional coatings onto a laser processed gap were examined for humidity sensing. Sol-gel, vacuum thermal evaporation and laser evaporation methods were used to obtain a thin layers of different materials.
Ultra-fast-prototyping of PMMA structures for micro-engineering applications: Choosing the right material
2017
Machining of poly(methyl methacrylate) (PMMA) by laser has been extensively studied in engineering research for several applications including microfluidic manufacturing and rapid prototyping. However, very few investigations have taken into consideration the wide range of physico-chemical characteristics of commercially available PMMA that can often affect the quality of the laser-machined structures. These characteristics are often ignored, with many manufacturing publications focusing on a single source of PMMA. To understand the different bonding strengths and laser-cut qualities in the context of our ultra-fast prototyping technique, four types of PMMA have been examined. Molecular wei…
Nano-Oxides produced by ns laser ablation in liquids
2014
Laser ablation in liquids was successfully applied to produce nanosized oxides from Si, Ti and Zn targets. The obtained colloidal solutions of nanoparticles were investigated by complementary techniques: AFM, IR and Raman spectroscopies; optical absorption and time resolved photoluminescence. The results demonstrate the production of SiO2, TiO2 and ZnO. The absorption and emission properties of these material have been also investigated and appear to be promising for optical applications.
Radio-frequency thermal ablation (RFTA) of small hepatocellular carcinoma in patients with cirrhosis. Experience at a single tertiary referral center
2005
AIM: Radio-frequency thermal ablation (RFTA) may prolong the survival of patients with small hepatocellular carcinoma (HCC) associated with cirrhosis. The aim of this study was to evaluate efficacy and safety of RFTA. METHODS: We performed the Kaplan-Meier analysis to estimate the survival rate in 69 consecutive patients with HCC (mean age 66+/-6.5 years; 44/25 male/female; 56 Child-Pugh class A and 13 Child-Pugh class B) treated by RFTA. A single lesion was observed in 60/69 (87%), two lesions in 8/69 (11.6 %), and 3 lesions in 1/69 (1.4 %) of patients. The tumor size was = or <3 cm in 60/69 (87%). RESULTS: Twenty-two patients died during follow-up. Overall survival rates were 81%, 66%, an…
Hepatocellular carcinoma recurrence in patients with curative resection or ablation: impact of HCV eradication does not depend on the use of interfer…
2016
none 48 no Background: In HCV-infected cirrhotic patients with successfully treated early hepatocellular carcinoma (HCC), the time to HCC recurrence and the effects of sustained viral eradication (SVR) by interferon (IFN)-based or IFN-free regimens on HCC recurrence remain unclear. Aim: To perform an indirect comparison of time to recurrence (TTR) in patients with successfully treated early HCC and active HCV infection with those of patients with SVR by IFN-based and by IFN-free regimens. Methods: We evaluated 443 patients with HCV-related cirrhosis and Barcelona Clinic Liver Cancer Stage A/0 HCC who had a complete radiological response after curative resection or ablation. Active HCV infec…
Laparoscopic Microwave Thermal Ablation for the Treatment of Hepatocellular Carcinoma in Chronic Hepatic Patients
2020
Background: Laparoscopic microwave thermal ablation (LMWTA) is a well-established alternative treatment to liver resection for treatment of liver tumors. The aim of this study was to describe our experience in LMWTA for hepatocellular carcinoma (HCC) in chronic hepatic patients. Materials and Methods: A study group of 61 consecutive HCC patients treated with LMWTA from January, 2013 to May, 2020 were considered for this study. Patient characteristics, liver function test, operational characteristics, and complications were recorded. Results: Of the 61 patients who underwent LMWTA, median age was 64 (interquartile range [IQR]: 58-71) years, mean body mass index was 26.2 (IQR: 23.2-29.4); 44 …