Ablation Plasma Research Articles

Transoral Robotic Surgery versus Plasma Ablation for Tongue Base Reduction in Obstructive Sleep Apnea: Meta-analysis.

To compare the effectiveness of transoral robotic surgery (TORS) versus plasma ablation (PA) in tongue base reduction surgery for obstructive sleep apnea (OSA). PubMed, Scopus, Cochrane Library, OVID. Keywords searched included OSA, tongue base surgery, TORS, and coblation. Outcomes included pre- to postoperative apnea-hypopnea index, Epworth Sleepiness Scale (ESS), and lowest oxygen saturation. Additional outcomes included surgical success rate, postoperative bleeding, operative time, and length of stay. A total of 690 unique articles were identified, of which 60 underwent full-text review. Twenty-six articles were included in final analysis, comprising 18 studies on TORS (834 patients) and 11 studies on PA (294 patients). Mean differences of apnea-hypopnea index, ESS, and lowest oxygen saturation for TORS were -23.92, -7.6, and 5.83% (all P < .01). Corresponding values for PA were -22.07, -4.14, and 5.48% (all P < .00001). TORS had greater ESS reduction than PA (P = .02). Follow-up duration was shorter in TORS than PA (mean ± SD: 4.2 ± 2.6 vs 4.6 ± 1.4 months, P = .0482). Surgical success rates in TORS and PA were similar (57.6% vs 60.3%, P = .4474). Postoperative bleeding occurred less frequently in TORS versus PA (3.3% vs 7.5%, P = .0103). Operative time was longer for TORS than PA (77.9 ± 16.4 minutes vs 44.0 ± 12.9 minutes, P < .0001). Length of stay was similar between TORS and PA (3.9 ± 1.6 days vs 3.9 ± 2.5 days, P = .9047). Tongue base reduction with TORS or PA each effectively treats OSA and provides comparable results. The choice between techniques might depend on patient factors, availability of technology, and associated costs.

Thermal damage and microstructure evolution mechanisms of Cf/SiBCN composites during plasma ablation

Ablation behavior and thermal damage mechanisms of Cf/SiBCN composites were investigated in plasma ablation flame under a heat flux of 4.02 MW/m2, simulating a hypersonic service environment at ∼2200 °C. Oxide layer formed on the composites surface effectively protects internal Cf/SiBCN composites from further ablation. However, the internal Cf/SiBCN composites endure severe thermal damage and complex reactions, leading to decomposition of SiBCN matrix and formation of α/β-SiC, β-Si3N4 grains, amorphous C layer and ring-like SiC layer. Based on detailed microstructure and phase composition analysis, thermal damage and microstructure evolution mechanisms of Cf/SiBCN composites during plasma ablation are clarified.

Feasibility study of a compact heavy ion source for investigation of laboratory magnetospheric plasma.

We are developing a laser ion source to provide a high brightness multi-charged heavy ion beam as a part of the heavy ion beam probe system, which will be used to diagnose plasma potential in the Ring Trap 1 device at the University of Tokyo. As a probe beam, Nb2+ was selected, and a detailed laser irradiation condition was explored. It was found that the laser power density of 1.2 × 109 W/cm2 gives the maximum particle number of Nb2+ per laser energy from a niobium foil target. Essential ablation plasma parameters to design the laser ion source were also obtained. The expected beam current was more than 12 mA/cm2, with a pulse width of 3.1 µs at 200 mm away from the target.

Effects of LaB6 on the microstructures and ablation properties of 3D C/C-SiC-ZrB2-LaB6 composites

Cf/LaB6 preform was used to prepare LaB6 doping C/C-ZrC-SiC composites by precursor infiltration and pyrolysis method, and effects of LaB6 on the microstructure and ablation resistance of C/C-SiC-ZrB2-LaB6 composites were investigated. Results show that LaB6 was reacted with Zr-precursor or its products to generate ZrB2 and other compounds. Thanks to the reactive sintering effect of LaB6, a compact ceramic skeleton was established in the substrate, which played a vital role in densifying and resisting ablation. The oxidation of the evenly-distributed La- and Zr-compounds produced the homogeneous oxide scale. The ternary phases of La2Si2O7, La0.71Zr0.29O1.65 and La2Zr2O7 were participated in the formation of the oxide scale, evolving the layer from SiO2 to SiO2-La2Si2O7 and then to SiO2-La2Si2O7-La0.71Zr0.29O1.65-La2Zr2O7-ZrO2 layer. After plasma ablation for 360 s, the mass and linear ablation rates were 0.3848 mg/s and 0.3694 μm/s, respectively. The seamless multi-phase layer can effectively prevent the composites from long-time ablation.

Time-resolved study of Bremsstrahlung emission and spectra at the early stage in a nanosecond laser ablated tungsten plasma

Laser-Induced Breakdown Spectroscopy (LIBS) has been considered as a crucial tool for element analysis in plasma wall interaction (PWI) of fusion devices. In this work, a one-dimensional gas-dynamic numerical model has been optimized to simulate the Bremsstrahlung emission and the spectral lines of W and W+ ranging from 180 nm to 450 nm at the early stage of plasma in a nanosecond laser ablation. In the literature, most of the researchers pay more attentions on the spectral lines but the Bremsstrahlung emission (continue background) is neglected. In our study, the relationship between plasma temperature and the continue Bremsstrahlung background is found. The numerical results show that the plasma Bremsstrahlung emission dominated in the early time of laser ablation but exponentially decreases from 10 ns to 160 ns. The intensity of spectral lines of W increase while that of W+ increase firstly, then decrease gradually from 10 ns to 160 ns. In addition, a Q-switch Nd:YAG pulsed laser with 8 ns FWHM and 1064 nm wavelength is used to experimentally study the plasma emission processes. The results indicate that the plasma Bremsstrahlung domains during the early stage of laser ablation, which is agreement with numerical prediction. The spatial integrated intensity of Bremsstrahlung, W-atomic line emission and W-ionic line emission were investigated. We hope that the results would provide a good guidance for optimizing LIBS application for PWI diagnosis of fusion devices.

Treatment of complex regional pain syndrome after filling a single bone-cyst cavity with beta-tricalcium phosphate granules

Backgrоund. Сomplex regional pain syndrome is a condition associated with a multitude of clinical factors. Its characteristic feature is persistent pain caused by injuries and is not anatomically limited to the location of a particular peripheral nerve.&#x0D; Clinical case. This article describes a case involving the treatment of complex regional pain syndrome in a thirteen-year-old patient, which resulted in a simple bone cyst surgical treatment of the lower-third of the fibula. Diagnostics were based on clinical, laboratorial, histological, radiological, and instrumental methods of research. The treatment methods included medication (nonsteroidal anti-inflammatory drugs, antidepressants, antipsychotics, anticonvulsants, non-opioid analgesics of central action, and bisphosphonates), cold plasma ablation, neurolysis of the sural nerve, prolonged regional anesthesia, tunneling of the bone marrow cavity (filled by substitutional filler), and marginal bone resection.&#x0D; Discussion. Сomplex regional pain syndrome is a poorly studied condition, which contributes to the complexity of its diagnosis. In this case, the presence of complex regional pain syndrome can be characterized by tissue injury during surgical intervention as well as by intraoperative injury of the nerve fibers. The stages of complex regional pain syndrome detected in studies may not appear in all patients, and in this case, no staging was observed. By eliminating the obliteration of the medullary canal after segmental resection of the sclerosed portion of the bone, it was possible to reduce the severity of pain, which resulted in the subsequent disappearance of the manifestations of complex regional pain syndrome.&#x0D; Conclusions. This case testifies to the effectiveness of various methods of treating complex regional pain syndrome. The etiology of the specific patients pain syndrome should be considered when treating complex regional pain syndrome.

Assessment machining of micro-channel textures on PCD by laser-induced plasma and ultra-short pulsed laser ablation

Micro-channels are one of the most common surface textures for applications, however, the machining of micro-channels on polycrystalline diamond (PCD) is still facing challenges due to its intrinsic properties of high brittleness and hardness. In this paper, fabrication of micro-channels by laser induced plasma (LIP) and laser ablation directly (LAD) machining methods on PCD surface is experimentally investigated. For comparing the processing capacity, the influence of different laser process parameters (including overlap, power, frequency, scanning speed and the number of passes) on the geometry and material removal rate of micro-channels is assessed. Results show that the process parameters have a significant influence on the formation of micro-channels, and LIP exhibits higher efficiency compared to LAD in the case of the plasma formation with the high overlap and laser power. The micro-channel depth and width produced by LIP increase with the increasing overlap, laser power and number passes, and that reduce with the increasing frequency and scanning speed; the MRR produced by LIP increases with the increasing overlap, laser power and scanning speed, and that reduces with the increasing frequency and number of passes. Meanwhile, LIP reduces the oxidation reaction inside the micro-channels compared to LAD due to the shielding effect of distilled water.

Thermodynamic Properties of Hydroxylammonium Nitrate-Based Electric Solid Propellant Plasma

Electric solid propellants are advanced solid chemical rocket propellants controlled by electric current. An electric solid propellant may also be used in an electric propulsion system: specifically, an ablative pulsed plasma thruster. Previous experiments with the electric solid propellant known as high-performance electric propellant, or HIPEP, suggest its ablation processes are similar to the traditional propellant polytetrafluoroethylene (). Better understanding of the ablation and the resulting propulsion performance of HIPEP requires a model of its vapor composition, bulk plasma quantities, and thermodynamic properties. Such a model was developed and favorably compared with previous analogous model predictions found in the literature for . The electric solid propellant vapor composition was predicted in the temperature range of 500–40,000 K at 1 bar pressure. Low temperatures (less than 2000 K) were dominated by water (), carbon dioxide (), and molecular nitrogen (), with results at 700 K matching to within 10% of the previous combustion model predictions. At high temperatures (greater than 25,000 K), the vapor was strongly ionized and dominated by carbon (), oxygen (), nitrogen (), and hydrogen () ions. The calculated enthalpy and specific heat were higher for high performance electric propellant (HIPEP) vapor than , suggesting increased thermal losses could be inherent to ablation-controlled HIPEP discharges.

The ablation of plastics by intense pulsed ion beam

With strong flash heating effects, intense pulsed ion beam (IPIB) may induce ablation on the solid surface and it is the basis of applications such as surface cleaning, nanopowder preparation and thin-film synthesis with IPIB. In this study, the ablation of polymethyl methacrylate (PMMA) by IPIB was investigated with varied beam energy density on pulsed ion beam accelerator BIPPAB-450 to study the ablation of IPIB under strong ablation. With thermal imaging measurement, it is revealed that when energy reaches a certain threshold, the ablation plume generated on the target surface may impose a shielding effect on the ion beam energy from depositing in the target. It is verified by thermal field simulation that for the low evaporation temperature and high thermal resistance, intense ablation plume may be generated on the surface of plastics under low IPIB energy density or at the early stage of IPIB irradiation. Ablation mass measurement demonstrated that under irradiation of IPIB with a pulse length of 120 ns, ion energy up to 450 keV, energy density up to 3.8 J/cm2, the mass loss of the target increases with the rise of IPIB energy density. Under the irradiation of a series of pulses, the mass loss of PMMA increases proportionally. Unlike ablation on metals by direct beam energy deposition, the ablation of plastics by IPIB endures more stages and the ablation may be more achieved by the heated ablation plasma by beam irradiation.

In-Situ Plasma Monitoring during the Pulsed Laser Deposition of Ni60Ti40 Thin Films

The properties of pulsed laser deposited of Ni60Ti40 shape memory thin films generated in various deposition conditions were investigated. In-situ plasma monitoring was implemented by means of space- and time-resolved optical emission spectroscopy, and ICCD fast camera imaging. Structural and chemical analyses were performed on the thin films using SEM, AFM, EDS, and XRD equipment. The deposition parameters influence on the chemical composition of the thin films was investigated. The peeled layer presented on DSC a solid-state transformation in a different transformation domain compared to the target properties. A fractal model was used to describe the dynamics of laser produced plasma through various non-differentiable functionalities. Through hydrodynamic type regimes, space-time homographic transformations were correlated with the global dynamics of the ablation plasmas. Spatial simultaneity of homographic transformation through a special SL(2R) invariance implies the description of plasma dynamics through Riccati type equations, establishing correlations with the optical emission spectroscopy measurements.

Laser power density dependence on charge state distribution of Ta ion laser plasma.

Laser power density per pulse, which is commonly expressed with the unit of "W/cm2," is an important parameter to characterize ablation plasma. To match a design charge state of heavy ion beam induced by a laser ion source, a laser power density must be carefully chosen. Above around 108 W/cm2 of laser power density, laser ablation plasma is emitted from the surface of solid material. Then, up to 109 W/cm2, the most abundant charge state is 1+. Because the ionization energy increases with higher charge states, increasing the laser intensity leads to the charge state distribution shifting higher. Increasing the density to increase charge states also results in lower time of flight due to higher velocities. The maximum laser power density is obtained by the smallest available laser spot size on the target material which is determined by the quality of the laser beam. For many accelerator applications, higher charge state beams are preferred. In particular cases, singly charge ion beams are demanded. Therefore, production of intermediate charge state beams has not been investigated well. In this study, we selected Ta4+ as an example demanded beam and tried to clarify how the transition of charge state distribution depends on laser power density. Conclusively, the possible specification of a laser ion source for Ta4+ delivery was elucidated.

Времяпролетная оптическая диагностика мощных импульсных ионных пучков

Ablation of a thin surface contamination layer is used to control fluencies of intense pulsed ion beams. The layer is self-restored after each ion pulse. An optical time-of-flight spectrometer measures velocities of the lightest components of the ablation plasma, hydrogen and carbon, to determine the ion fluence.

Экспериментальное исследование пространственно-зарядовой структуры и динамики разлета сгустка плазмы лазерной абляции

Экспериментальное исследование пространственно-зарядовой структуры и динамики разлета сгустка плазмы лазерной абляции

96Zr beam production for isobar experiment in relativistic heavy ion collider.

To investigate the chiral magnetic effect, 96Zr and 96Ru beams were accelerated at the relativistic heavy ion collider (RHIC) during Run-18 at Brookhaven National Laboratory. The 96Zr beam was provided from the electron beam ion source (EBIS) injector, which consists of a laser ion source, an EBIS high charge state ion breeder, a 300 keV/u radio frequency quadrupole, and a 2 MeV/u interdigital H type drift tube linear accelerator (IH-DTL). The natural abundance of 96Zr is only 2.8% with about 50% of 90Zr. To obtain a sufficient beam current, Zr material enriched to about 60% of 96Zr was used. The only available form of the enriched material was zirconium oxide (ZrO2) powder, which was not well suited for a laser ion source target. We studied and established a sintering technique of the ZrO2 powder to make a solid sample which could be installed into the laser ion source. The singly charged Zr was produced in a laser ablation plasma, extracted, and delivered to the EBIS to be ionized further to 96Zr16+. We optimized the laser irradiation condition, the EBIS confinement time, and transport through the RF linacs to maximize the performance of the injector. The total number of shots provided from the laser ion source for injection into the EBIS was 489 910. The EBIS facility provided a 192 MeV stable beam of 96Zr16+ ions to the booster ring of alternating gradient synchrotron (AGS) for further acceleration and stripping in the AGS/RHIC complex, allowing for successful data acquisition at the Solenoidal Tracker at the RHIC.

Thin films prepared by a hybrid deposition configuration combining two laser ablation plasmas with one sputtering plasma

A hybrid configuration for multicomponent thin film deposition by combining two laser ablation plasmas with one sputtering plasma is presented. This setup was used to deposit TiO2 thin films modified simultaneously with Bi and Pt. In order to investigate the effect of the metal incorporation in titania the deposited films were characterized by X-ray photoelectron, Raman, UV–Vis and photoluminescence spectroscopies, as well as by X-ray diffraction and scanning electron microscopy. The results showed that films with different load of Bi and Pt were obtained. The amount of these metals has an important effect on the compositional, structural and optical properties of the deposited films. Mixtures of TiO2 with Bi2O3 as well as metallic Bi and Pt are obtained at the highest Pt content. The index of refraction and band gap decrease as the Pt content increases making these films capable to absorb light from the visible region of the solar spectrum with potential applications as photocatalysts to degrade organic pollutants present in wastewaters.

Dynamics and its modulation of laser-induced plasma and shockwave in femtosecond double-pulse ablation of silicon

The dynamics of laser-induced plasma and shockwave was studied using time-resolved shadowgraphy in femtosecond double-pulse ablation of silicon. The morphology and expansion distances of laser-induced plasma and shockwave can be controlled by adjusting the pulse delay. The underlying mechanism was interpreted in terms of suppressed laser-induced air breakdown and enhanced laser energy deposition. The former is proposed to reduce the expansion distance in the longitudinal direction for small pulse delay, while the latter is the dominant mechanism for increasing the expansion distance in the longitudinal and radial directions for pulse delay exceeding a few picoseconds.

Target properties – Plasma dynamics relationship in laser ablation of metals: Common trends for fs, ps and ns irradiation regimes

Better understanding of complex relationships between laser-produced plasma dynamics and ablation target material properties is key for optimization of numerous technological and analytical applications. Continuing a previous work [Irimiciuc et al., Appl. Surf. Sci. 417 (2017) 108–118] which proposed empirical laws for some of these relationships (in femtosecond irradiation regime), we present here a systematic study on several metallic targets (Al, Cu, Mn, Ni, Ti, Zn) irradiated by nanosecond, picosecond and femtosecond laser pulses. The experimental approach is based on complementary diagnostics, with the implementation of both electrical and optical techniques for transient plasma characterization. The empirical equations previously reported for femtosecond ablation pulses are now extended to the picosecond and nanosecond regimes.

Microchannel Fabrication in Fused Quartz by Backside Laser-Induced Plasma Ablation Using 248 nm KrF Excimer Laser

Laser-induced plasma ablation (LIPA) using a 248 nm KrF excimer laser was investigated for microchannel fabrication. Examination of the morphology in relation to ablation performance was emphasized, and a synthetic LIPA mechanism model was proposed based on the results. Backside LIPA with a metal target on the bottom can be attributed to a combination of two phenomena: laser-induced plasma vaporization thermal ablation from the metal target below and enhanced laser–glass direct interaction from the plasma residuum. The laser absorption enhancement of quartz substrate resulting from the metal residuum was validated clearly using absorption spectrum measurements. The influence of laser parameters on the etching quality during LIPA was also analyzed for processing optimization. Finally, fused quartz glass microchannels of outstanding surface quality and dimension uniformity were implemented. The channel depth was 28 μm, and the bottom surface roughness was better than several hundred nanometers.

Investigations of Laser Produced Plasmas Generated by Laser Ablation on Geomaterials. Experimental and Theoretical Aspects

Several surface investigation techniques, such as X-ray diffraction (XRD), EDX, and optical microscopy, were employed in order to describe the mineral contents in several geomaterials. Space and time resolved optical emission spectroscopy was implemented to analyze the plasma generated by the laser–geomaterial interaction. The values of the plasma parameters (velocity and temperature) were discussed with respect to the nature of the minerals composing the geomaterials and the morphological structure of the samples. Correlations were found between the excitation temperatures of the atomic and ionic species of the plasmas and the presence of calcite in the samples. A mathematical model was built to describe the dynamics in ablation plasma using various mathematical operational procedures: multi structuring of the ablation plasma by means of the fractal analysis and synchronizations of the ablation plasma entities through SL (2R) type group invariance and in a particular case, through self-modulation in the form of Stoler type transformations. Since Stoler type transformations are implied in general, in the charge creation and annihilation processes, then the SL (2R) type group invariance become fundamental in the description of ablation plasma dynamics.

Effect of resection of adenoids and/or tonsil on the immune indexes in children with obstructive sleep apnea hypopnea syndrome

Objective: To study the effect on immune indexes in children with obstructive sleep apnea hypopnea syndrome (OSAHS) before and after resection of adenoid and/or tonsil. Methods: A total of 100 children with OSAHS due to adenoid hypertrophy were enrolled in Department of Otorhinolaryngology Head and Neck Surgery, the Second Hospital of Dalian Medical University from December 2016 to December 2018. Some cases were complicated with tonsil hypertrophy or chronic tonsillitis. 6 ml of fasting peripheral venous blood were collected from all subjects at the 1st day before surgery, 4th day, 1 month, 3 months and 6 months after surgery to detect lymphoid subsets percentage (CD3(+), CD4(+),CD8(+), CD4/CD8, CD19, NK) and level of immunoglobulin (IgG, IgA, IgM). Grouping: group A was a total of 51 cases with adenoid hypertrophy after Adenoid plasma ablation; group B was a total of 27 cases with adenoid hypertrophy and chronic tonsillitis after plasma ablation of adenoid and tonsil; and group C was a total of 22 cases hypertrophy of adenoid and tonsil after plasma ablation of adenoid and tonsil.In the baseline data, age, gender and other variables were analyzed by anova and chi-square test, repeated measurement anova was used for intra-group and inter-group comparison of observation indicators at different time points after operation, and independent sample t-test was used for comparison between the two groups at observation points 3 months after operation. Results: (1) In group A, the percentage of CD19 lymphocytes before surgery was higher than that at 4th day after surgery, and the difference was statistically significant (21.85±6.20 vs.19.18±5.91, P<0.05). The other immune indexes were not statistically different before and after surgery (P>0.05). (2) In group B, the percentage of CD19 lymphocytes, CD3(+)T lymphocytes, CD8(+)T lymphocytes and the level of IgG at 4th day after surgery were significantly different between those before surgery (all P<0.05). At the 1st month after surgery, the percentage of CD3(+)T lymphocytes, CD8(+)T lymphocytes, CD19 lymphocytes and the level of IgG were significantly different between those before surgery (all P<0.05). The other immune indexes were not statistically different before and after operation (P>0.05). (3) In group C, the percentage of CD19 lymphocytes and the CD3(+)T lymphocytes at 4th day after surgery were significantly different between those before surgery (all P<0.05).In the 1st month after surgery, the percentage of CD8(+)T lymphocytes and CD19 lymphocytes were significantly different between those before surgery (all P<0.05). The other immune indexes were not statistically different before and after operation (P>0.05). (4) Among three groups, the percentage of CD4(+)T lymphocytes, the levels of IgG and IgA before surgery between group A and Group B were statistically significant (all P<0.05). At 4th day after surgery, the percentage of CD4(+)T lymphocytes in group B and C were lower than those in group A, and the differences were statistically significant (32.22±6.14, 32.36±6.87 vs. 36.36±5.19, all P<0.05); the other immune indexes were not statistically different among each group before and after surgery (P>0.05). Conclusions: Resection of adenoid has no significant effect on the immune indexes in children with OSAHS. The children with OSAHS complicated with tonsil problems have immune index disorder before surgery. Surgery has a certain effect on the immune indexes of children with OSAHS in a short period of time, and tends to normal level after one month.