Ablation Characteristics Research Articles

Wavelength dependence of the ablation characteristics of Cu (In, Ga) Se2 solar cell films and its effects on laser induced breakdown spectroscopy analysis

As a novel method for fast depth profile analysis of Cu (In, Ga) Se2 (CIGS) thin film solar cell, laser induced breakdown spectroscopy (LIBS) is introduced, and the effects of laser wavelength on depth resolution are investigated. From LIBS analysis of a commercial CIGS solar cell using an ultraviolet (λ = 266 nm) and a visible (λ = 532 nm) nanosecond Nd: YAG lasers and an intensified charge-coupled device spectrometer, it is shown that the use of a shorter wavelength laser does not guarantee an enhancement of depth resolution. Although the averaged ablation depth per pulse was smaller for the ultraviolet laser, the craters produced by the visible laser was much smoother and more uniform, demonstrating that depth resolution depends not only on laser wavelength but also strongly on the ablation mechanisms.

Ablation damage assessment of aircraft carbon fiber/epoxy composite and its protection structures suffered from lightning strike

Aircraft carbon fiber/epoxy composite material is sensitive to lightning strike. Its damage assessment and protection design suffered from lightning strike is becoming increasingly important. Four different types of carbon fiber/epoxy composite laminates are selected, which are without protection, with full spraying aluminum coating, with local spraying aluminum coating and with spraying aluminum coating on glass cloth pasted to fastener head, respectively. Impulse electrical current tests were performed by implementing electrical current waveforms with different peak values with regard to different lightning zonings. Three-dimensional finite element models of composite laminate and its protection structures are accurately built to assess lightning ablation characteristics based on the coupled thermal/electrical/structural analysis and element deletion method, in which different electrical and thermal physical properties of the elements are defined depending on different temperature conditions. The results show that simulation results are good agreement with experimental results. Fiber damaged area, the damaged area and the maximum damaged thickness increases with the increase of electrical current peak. Aluminum coating has a good effect on anti-lightning strike. The thicker aluminum layer and the better to anti-lightning strike.

Effects of optical absorbance with ablation characteristics in femtosecond laser irradiation of carbon reinforced Al2O3 composites

The thresholds and depths of ablation of carbon [carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs)] reinforced Al2O3 composites were compared and correlated with those of monolithic Al2O3 using femtosecond pulsed laser irradiation (λ = 1027 nm, τP = 380 fs). These composites were processed using a spark plasma sintering method (Ts = 1500°C, τs = 10 min and P = 40 MPa) through which highly densified (more than 97%) composites were fabricated. The optical absorbance of each composite improved in the wavelength range from ultraviolet to near infrared. Compared with the corresponding values for monolithic Al2O3, the ablation thresholds of CNT/Al2O3 and GNP/Al2O3 were 50 and 75% lower respectively, and their ablation depths were two to three times deeper.

Commissioning of a high enthalpy plasma facility for testing plasma facing materials in a fusion reactor

A high enthalpy, 400kW plasma testing facility was constructed at Chonbuk National University (CBNU) in Korea. Enhanced segmented arc plasma torches are used as the plasma sources, allowing it to produce enthalpies greater than 10MJ/kg. An ablation test of a carbon-based plasma facing material (PFM) was conducted at the plasma facility and the ablation characteristics were investigated. This facility produces particle flux greater than 1024/(m2s) and heat flux greater than 10MW/m2, that are relevant for testing PFM under fusion reactor conditions.

Ablation characteristics of quantum square pulse mode dental erbium laser.

Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

0029: Redo-ablations of atrial fibrillation: procedural characteristics depending on the choice of cryoenergy or radiofrequency ablation as the first line therapy

Pulmonary vein (PV) isolation has become a cornerstone therapy for symptomatic paroxysmal AF refractory to anti-arrhythmic drugs. Nowadays, the most common energies used to achieve PV isolation are cryoenergy and radiofrequency (RF). However, approximately one third of the patients have recurrences, mainly due to PV reconnections. Little is known about the characteristics of the redo procedure, depending on the choice of the initial energy. Patients referred to our center for a RF redo ablation procedure of symptomatic paroxysmal AF (PxAF) between 2010 and 2014 were retrospectively enrolled. Demographic data and characteristics of the initial ablation, i.e. cryoenergy or RF ablations, were collected. Number and location of PV gaps, and redo characteristics were reviewed. 74 patients scheduled for a redo ablation of AF were included, 38 and 36 using RF or cryoablation for the first procedure, respectively. For the initial ablation, procedural and fluoroscopy times were significantly shorter when using cryoenergy (147.8±52.6 vs. 226.6±64.3 min, p<0.001, and 37.0±17.7 vs. 50.8±22.7 min, p=0.005, respectively). Overall, an identical number of gaps were found during redo procedures of cryo and RF ablations. However, a significantly higher number of gaps were located in the right superior PV (RSPV) for patient first ablated with RF (0.9±1.0 vs. 0.5±0.9, p=0.009). The location of gaps was different, predominantly found in the anterior and superior parts of the left superior PV (LSPV), the anterior and inferior part of the left inferior PV (LIPV), the superior part of the right superior PV (RSPV), and in the postero-inferior part of the right inferior PV (RIPV) when using RF as the initial energy. For patient first ablated with cryoenergy, gaps were predominantly found in the anterior part of the left PV, evenly distributed in the RSPV, and in the postero-inferior part of the RIPV. Although not significant, redo procedures of cryoablations were slightly shorter and needed less RF duration times to achieve PV isolation (160.0±55.7 vs. 175.7±59.1 min, p=NS, and 954.1±796.7 vs. 1476.7±1269.6, p=NS). During redo procedures, gaps location pattern is different for patients first ablated with cryo or RF energy, and RSPV reconnections occur more frequently after RF ablation, probably due to poor contact in this region. Procedural characteristics of the redo ablation are similar. Abstract 0029 – Figure: Localization of gaps, during the redo procedure

真空环境下脉冲激光烧蚀等离子体羽流特性分析

真空环境下脉冲激光烧蚀等离子体羽流特性分析

真空环境下脉冲激光烧蚀等离子体羽流特性分析

真空环境下脉冲激光烧蚀等离子体羽流特性分析

齲蝕の選択的除去に向けた波長2.94および5.80μmのナノ秒パルスレーザーによるウシ脱灰象牙質切削特性の比較

齲蝕の選択的除去に向けた波長2.94および5.80μmのナノ秒パルスレーザーによるウシ脱灰象牙質切削特性の比較

Catheter ablation of atrial fibrillation in patients with concomitant sinus bradycardia—Insights from the German Ablation Registry

AimsThis investigation addresses procedural characteristics of catheter ablation in patients with atrial fibrillation (AF) and sinus bradycardia. MethodsFrom the prospective, multi-center German Ablation Registry 1073 patients with sinus rhythm at the time of AF ablation were divided into two groups according to heart rate at start of procedure (A, <60 beats per minute (bpm), n=197; B, 60–99bpm, n=876). ResultsAcute procedural success was high (≥98%) and similar between groups. Procedure duration and energy application time were increased in group A (180min vs. 155min and 2561s vs. 1879s, respectively). Major complications were more frequent in group A (2.2% vs. 0.5%), and a greater proportion of these patients was discharged under antiarrhythmic medication (64% vs. 52%). ConclusionCatheter ablation of AF with concomitant sinus bradycardia is associated with high procedural efficacy, longer procedure- and energy application durations, and a slightly elevated complication rate.

A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

This paper presents an investigation on the ablation characteristics of excimer laser (λ=248nm, τ=15ns) and femtosecond laser (λ=800nm, τ=100fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth=0.087J/cm2) than that for the femtosecond laser ablation of ABS (Fth=1.576J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α−1=223nm) than that for femtosecond laser ablation (α−1=2917nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the CC bond completely through the chain scission process whereas CC bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the CC bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (CO and CO bond) and nitrogen-rich (CN) functional groups.

Ablation and thermo-mechanical tailoring of EPDM rubber using carbon fibers

Abstract Carbon fibers (CFs) are incorporated into ethylene propylene diene monomer (EPDM) rubber to fabricate charring elastomeric ablative composites for ultrahigh temperature applications. Ablation characteristics of the ablative composites were evaluated using ASTM E285-08. Variant content incorporation of short CFs in the basic composite formulation reduced the backface temperature acclivity and the ablation rate rose up to 48% and 78%, correspondingly. Thermal stability and endothermic capability were improved with increasing short fiber contents in the rubber matrix. Experimental thermal conductivity measurement results elucidate that thermal conductivity reduces 60% at 473 K with 6 wt% addition of the fibers. A remarkable improvement was scrutinized in the tensile strength and rubber hardness with increasing fiber to matrix ratio. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis of the composite specimens revealed the uniform dispersion of CFs within the host matrix, formation of voids during ablation, char-reinforcement interaction and composition of the charred ablators and the impregnated fibers.

Orbital and physical characteristics of meter-scale impactors from airburst observations

We have analyzed the orbits and ablation characteristics in the atmosphere of 59 Earth-impacting fireballs, produced by meteoroids 1m in diameter or larger, described here as meter-scale. Using heights at peak luminosity as a proxy for strength, we determine that there is roughly an order of magnitude spread in strengths of the population of meter-scale impactors at the Earth. We use fireballs producing recovered meteorites and well documented fireballs from ground-based camera networks to calibrate our ablation model interpretation of the observed peak height of luminosity as a function of speed. The orbits and physical strength of these objects are consistent with the majority being asteroidal bodies originating from the inner main asteroid belt. This is in contrast to earlier suggestions by Ceplecha (Ceplecha, Z. [1994]. Astron. Astrophys. 286, 967–970) that the majority of meter-tens of meter sized meteoroids are “…cometary bodies of the weakest known structure”. We find a lower limit of ∼10–15% of our objects have a possible cometary (Jupiter-Family comet and/or Halley-type comet) origin based on orbital characteristics alone. Only half this number, however, also show evidence for weaker than average structure. Two events, Sumava and USG 20131121, have exceptionally high (relative to the remainder of the population) heights of peak brightness. These are physically most consistent with high microporosity objects, though both were on asteroidal-type orbits. We also find three events, including the Oct 8, 2009 airburst near Sulawesi, Indonesia, which display comparatively low heights of peak brightness, consistent with strong monolithic stones or iron meteoroids. Based on orbital similarity, we find a probable connection among several events in our population with the Taurid meteoroid complex; no other major meteoroid streams show probable linkages to the orbits of our meter-scale population. Our impactors cover almost four orders of magnitude in mass, but no trend in height of peak brightness as a function of mass is evident, suggesting no strong trend in strength with size for meter-scale impactors consistent with the results of Popova et al. (Popova, O.P. et al. [2011]. Meteorit. Planet. Sci. 46, 1525–1550).

Precise micromachining of yttria-tetragonal zirconia polycrystal ceramic using 532 nm nanosecond laser

High quality micro-sized steps and blind hole structures without microcracks, chips or spatter deposition were machined on yttria-tetragonal zirconia polycrystal (Y-TZP, 3mol% yttria) by nanosecond laser (wavelength=532nm, pulse width ~6ns). The diameter of blind hole is 500μm and each step is 500±10μm wide and 100±5μm deep. The 1.35mm3/min removal rate and the smooth machined surface with Ra=2.824μm roughness depicting the high precise and efficient processing were achieved. The ablation characteristics of nanosecond laser process of Y-TZP ceramic were also studied. Based on the study, a reasonable design of the processing path for micromachining of a finer embedded step with 24±2μm width (smaller than the 60μm focused spot size) around the inner-wall of a 2×2mm2 cavity was developed. These results and discussion offer new possibilities in the manufacturing of bio-ceramic products by nanosecond laser with high processing quality and efficient.

Characteristics of laparoscopic microwave ablation with renal tissue: Experimental in vivo study using a porcine model

Purpose: A model of in vivo porcine kidneys is used to clarify the characteristics of laparoscopic microwave ablation (MWA) of renal tissue. Materials and methods: Six pigs were utilised for the experiment using 18G water circulating-cooling microwave needles. The operating frequency was 2450 MHz, and the independent variables were power (50–60 W) and time (300–600 s). The kidneys were dissociated laparoscopically and ablated with a single or double needle at different power/time combinations and depths of puncture. Changes in the kidneys were carefully observed. Specimens of the ablated lesions were stained with haematoxylin-eosin (H&E) to evaluate the pathological features. Results: Thirty-four thermoablations were applied. The effective ablation shape was similar to a chestnut. The ablated lesions could be divided into three zones: carbonization zone, coagulation zone, and inflammatory reaction zone. The ablation zone enlarged with increasing power and time. When combined with two needles, the maximum diameter of the ablated lesions significantly increased. Pathological results indicated that renal tissues of the carbonisation zone were thoroughly necrotic. Coagulative necrosis was observed in the coagulation zone. No ‘skipped’ areas were noted in any ablation zone. The structure of the inflammatory reaction zone was integrated, and interstitial small blood vessels were highly expanded and congested with infiltrated inflammatory cells. Conclusions: MWA achieved excellent effects in this porcine model. It can be safely and effectively used in renal tissue. For patients with poor physical condition or small renal masses (<4 cm), we can refer to these data and select the appropriate combinations to obtain satisfactory therapeutic efficacy.

Research advances of anti-tumor immune response induced by pulse electric field ablation

As a novel tumor therapy, pulse electric field has shown a clinical perspective. This paper reviews the characteristics of tumor ablation by microsecond pulse and nanosecond pulse electric field, and the research advances of anti-tumor immune response induced by pulse electric field ablation. Recent researches indicate that the pulse electric field not only leads to a complete ablation of local tumor, but also stimulates a protective immune response, thereby inhibiting tumor recurrence and metastasis. These unique advantages will show an extensive clinical application in the future. However, the mechanism of anti-tumor immune response and the development of related tumor vaccine need further studies.

Atrial Tachycardias Following Persistent Atrial Fibrillation Ablation: Predictors of Recurrence After the Repeat Ablation.

Repeat procedures after persistent atrial fibrillation (AF) ablation are frequently performed for secondary atrial tachycardias (AT). Predictors of AT recurrence after the first repeat ablation have not yet been studied. We investigated predictors of AT recurrence in 117 patients who underwent ablation for secondary AT arising after a previous ablation for persistent AF using the Cox proportional hazards model. Acute ablation success rate was 94%. Over a follow-up period of 12 months, 61 patients (53%) were free from AT recurrence. Of the assessed predictors of AT recurrence, the number of ablated AT forms (>1 vs. 1) was significantly associated with AT recurrence (hazard ratio 2.01, 95% CI 1.18-3.43, P = 0.01). Other variables including left atrial diameter, AT mechanism, or the characteristics of previous AF ablation did not have significant influence on AT recurrence (P>0.05). Men had a tendency toward fewer AT recurrences than women (OR 0.60, 95% CI 0.34-1.05, P = 0.07). During a second AT ablation procedure, 19 (49%) patients were identified to have a recurrence of the previously ablated AT, whereas in 20 patients (51%) a new AT form was diagnosed. Ablation of atrial tachycardias following persistent AF ablation has a high acute success rate. However, a substantial number of patients develop new onset AT during follow-up. The occurrence of multiple AT forms during the repeat ablation procedure was the only predictive factor for AT recurrence.

Experimental study on ablation zone and characteristics of microwave ablation in porcine kidney in vitro

To observe the ablation zone and characteristics of microwave ablation with different power and time in the model of porcine kidneys in vitro. 2 450 MHz water circulative-cooling microwave needles were used, and the length of the anterior pole was 1.10 cm. The independent variables were power (50-70 W), time (240-600 s) and ablated with different combinations. The ablation shape, zone and pathological characteristics were observed. The effective ablation shape was similar to a chestnut and the ablation zone enlarged with the increasing of power and time. When combined with 50 W/480 s, 60 W/300 s, 70 W/240 s, the largest transverse-diameter of the ablated tissue was close to 3.00 cm and the length-diameter was about 3.30 cm. The pathological characteristics indicated that renal tissues of carbonization zone were thoroughly necrotic.Coagulative necrosis was observed in coagulation area, though there were residual profile of glomerulus, renal tubular and vessels, they had lost activity. Most of the tissues in transition zone were normal, however, some cells were swelling because of thermal damage. Microwave ablation is an emerging thermal therapy which can be safely, effectively used in the treatment of renal tumors that are smaller than 3 cm.

Ablation Characteristics of Bovine Liver According to Cool-Tip Temperature of RFA Equipment

Ablation Characteristics of Bovine Liver According to Cool-Tip Temperature of RFA Equipment

Impact of freezing time and balloon size on the thermodynamics and isolation efficacy during pulmonary vein isolation using the second generation cryoballoon.

The differences in ablation characteristics of freezing time and balloon size using second generation cryoballoon are still unknown. Twenty-six dogs underwent pulmonary vein (PV) isolation. Balloon and tissue temperatures (left atrial-PV junction, phrenic nerve, and internal esophagus) were monitored. The ablation duration was randomized to either 3 or 4 minutes, which did not show significant differences in temperature profiles, PV isolation success rate, complications, or histological changes. Twenty dogs underwent cryoablation using 28-mm cryoballoon, 6 dogs were done using the 23-mm cryoballoon. Positioning of the 23-mm cryoballoon was more distal in the PV, which resulted in better PV occlusion. Temperature profiles showed lower temperatures in the 23-mm cryoballoon than in the 28-mm cryoballoon (inner balloon, median [range]: -51.5 [-66.0 to -31.0] versus -43.0 [-64.0 to -26.0]°C, P<0.001; balloon surface: -43.0 [-60.0 to -15.8] versus -6.5 [-46.2 to 28.9]°C, P<0.001; left atrial-PV junction: -6.7 [-20.0 to 21.4] versus 15.8 [-14.4 to 35.1]°C, P<0.001), and trended toward a higher PV isolation success rate in the 23-mm cryoballoon. Histologically, deeper extensions of ablative lesions into the PV were seen with 23-mm cryoballoon, and larger ablative lesions were seen in the left atrial antrum using 28-mm cryoballoon. The efficacy of 3-minute ablation was not significantly different from 4-minute ablation in dogs. The 23-mm cryoballoon had a greater cooling effect than the 28-mm cryoballoon for small PVs, but showed narrower ablative lesions in the left atrial antrum.