Ms Pulse Duration Research Articles

The effect of peripheral high-frequency electrical stimulation on the primary somatosensory cortex in pigs.

This study implements the use of Danish Landrace pigs as subjects for the long-term potentiation (LTP)-like pain model. This is accomplished by analyzing changes in the primary somatosensory cortex (S1) in response to electrical stimulation on the ulnar nerve after applying high-frequency electrical stimulation (HFS) on the ulnar nerve. In this study, eight Danish Landrace pigs were electrically stimulated, through the ulnar nerve, to record the cortically evoked response in S1 by a 16-channel microelectrode array (MEA). Six of these pigs were subjected to HFS (four consecutive, 15 mA, 100 Hz, 1000 µs pulse duration) 45 min after the start of the experiment. Two pigs were used as control subjects to compare the cortical response to peripheral electrical stimulation without applying HFS. Low-frequency components of the intracortical signals (0.3–300 Hz) were analyzed using event-related potential (ERP) analysis, where the minimum peak during the first 30–50 ms (N1 component) in each channel was detected. The change in N1 was compared over time across the intervention and control groups. Spectral analysis was used to demonstrate the effect of the intervention on the evoked cortical oscillations computed between 75 ms and 200 ms after stimulus. ERP analysis showed an immediate increase in N1 amplitude that became statistically significant 45 mins after HFS (p < 0.01) for the intervention group. The normalized change in power in frequency oscillations showed a similar trend. The results show that the LTP-like pain model can be effectively implemented in pigs using HFS since the cortical responses are comparable to those described in humans.

The effect of reversible permeabilization and post-electroporation resting on the survival of Thai basil (O. Basilicum cv. thyrsiflora) leaves during drying

Horticultural crops have a low tolerance to dehydration. In this paper, we show that the reversible electroporation (200 monopolar, rectangular pulses of 50 µs pulse duration, 760 µs between pulses and nominal field strength of 650 V/cm) of Thai basil leaves followed by 24 h resting before hot air drying at 40 °C enhanced the survivability of the tissues at certain levels of dehydration (moisture ratio = 0.2 and 0.1). However, this increased survival was rather limited. Through measurements of metabolic heat production during resting, rehydration kinetics, respiration and photosynthesis of the rehydrated leaves, we show that resting after the application of a reversible pulse-electric field (PEF) may allow a phase of hardening that has a protective effect on the cells, thus decreasing damage during the subsequent drying phase. Increased preservation of cell vitality would be associated with a more turgid and fresh-like rehydrated product, as cells would have the capacity to retain the rehydration water.

Electroporation of suspension cell lines – A proposed assay set for optimizations

To make in vitro single cell electroporation protocols more comparable between various cancer types and groups, we propose a set of assays to test a range of electric field strengths at the start of any new project to determine the optimal electric field strength for a given cell line. While testing a range of electric field strengths, we kept the other ESOPE parameters constant (8 pulses, 100 µs pulse duration, 1 Hz pulse frequency). Basic assays were employed to measure short-term viability, effectiveness of treatment, metabolic activity, and recovery potential post-treatment to determine the optimal field strength for a particular cell line. Six cancer cell lines were tested, three of human (A549, A375 and Pan02) and three murine (LLC, B16F10 and MIA-PACA2). Our findings demonstrate that the optimal electroporation setting while keeping with all other ESOPE parameters are 800 V/cm for A549 and Pan02, 700 V/cm for A375, Mia-PACA2, and B16F10, and 1300 V/cm for LLC. Having an agreed upon set of assays to determine each cell lines optimal electric field strength should allow an improve translation of findings between cell lines for in vitro work from various groups and potentially improve translation into the clinic.

Investigation on surface roughness and hardness of β-Ti alloy by ball burnishing assisted electrical discharge cladding for bio-medical applications

In the current study, a comparative study on the surface modification of β-Phase titanium alloy has been carried out using electric discharge machining (EDM) and ball burnishing assisted electrical discharge cladding (BB-EDC) process to improve the surface hardness and surface finish for the potential use of biomedical implants. The surface characteristics of Edmed and BB-EDC modified surface has been investigated. The effect of EDM and BB-EDC process parameters such as peak-current, pulse-duration and supply-voltage on the surface roughness and micro-hardness has been studied. The roughness was measured using a surface profilometer and surface hardness was measured using Vicker’s micro-hardness tester. The results show that BB-EDC modified surface exhibits high surface hardness and low surface roughness as compared with EDMed surface at any parametric condition. The in the case of BB-EDC, the maximum surface hardness (848HV) and minimum surface roughness (0.56 µm) were obtained at 5A peak current, 50 µs pulse duration, and 60 V supply voltage. Moreover, the recast layer obtained after BB-EDC process was flat and smooth with 10–15 µm thickness. The obtained surface from BB-EDC process was free from defects and can be used for biomedical implant application.

Electrochemical safety limits for clinical stimulation investigated using depth and strip electrodes in the pig brain

Objective. Diagnostic and therapeutic electrical stimulation are increasingly utilized with the rise of neuromodulation devices. However, systematic investigations that depict the practical clinical stimulation paradigms (bipolar, two-electrode configuration) to determine the safety limits are currently lacking. Further, safe charge densities that were classically determined from conical sharp electrodes are generalized for cylindrical (depth) and flat (surface grid) electrodes completely ignoring geometric factors that govern current spreading and trajectories in tissue. Approach. This work reports the first investigations comparing stimulation limits for clinically used electrodes in two mediums: in benchtop experiments in saline and in vivo in a single acute experiment in the pig brain. We experimentally determine the geometric factors, the water electrolysis windows, and the current safety limits from voltage transients, for the sEEG, depth and surface strip electrodes in both mediums. Using four-electrode and three-electrode configuration measurements and comprehensive circuit models that accurately depict our measurements, we delineate the various elements of the stimulation medium, including the tissue-electrode interface impedance spectra, the medium impedance and the bias-dependent change in the interface impedance as a function of stimulation parameters. Main results. The results of our systematics studies suggest that safe currents in clinical bipolar stimulation determined in vivo can be as much as 24 times smaller than those determined from benchtop experiments (for depth electrodes at a 1 ms pulse duration). Our detailed circuit modeling attributes this drastic difference in safe limits to the greatly dissimilar electrode/tissue and electrode/saline impedances. Significance. We established the electrochemical safety limits for commonly used clinical electrodes in vivo and revealed by detailied electrochemical modeling how they differ from benchtop evaluation. We argue that electrochemical limits and currents are unique for each electrode, should be measured in vivo according to the protocols established in this work, and should be accounted for while setting the stimulation parameters for clinical applications including for chronic applications.

The Influence of Short Pulse Er:Cr: YSGG Laser on the Shear Bond Strength of Cad-Cam Zerconia Material to Resin Cement

Background: Surface enhancement of CAD-CAM zerconia for increasing the matching to resin cement, using Er:Cr:YSGG Laser.Materials and Methods: 40 sintered zerconia disc specimens( VITAYZ HT) were prepared. They are dividedinto six groups, each group of seven samples.Laser groups are depending on laser power, laser irradiation time and pulse duration, group(A): 20 s, 60µs pulse duration. Group (B): 30 s , 60 µs pulse duration. Group (C): 40 s, 60 µs pulse duration. Group (D): 20 s, 700 µs pulse duration. And group (E): 30 s, 700 µs pulse duration, for different powers (1, 1.50, 2, 2.50, 3, 3.50, 4) W.Luting cementwas bonded to treated zerconia surfaces and light cured for 40 s.The Shear bond strength was measured using a universal testing machine. The optained results were stastistically analyzed. Thebond failur modes were also examined.Results: There was a clear increment in the shear bond strength especielly in group B (4 W, 30 s,60 µs) reaching to 8.63 Mpa.No crackes were observed.Conclusion: It was detected that the shear bond strength was related to the pulse depth.The pulse duration of Er:Cr:YSGG is a crucial parameter in the enhancement of zirconia ceramic surface.

Optogenetic diaphragm muscle activation in mice

Breathing impairments are the leading cause of morbidity and mortality across all forms of neuromuscular disease. When voluntarily diaphragm activation is insufficient, clinical options include mechanical ventilation or electrical stimulation via intramuscular wires. Here we tested the hypothesis that an optogenetic approach would enable light to serve as an adequate stimulus for inducing diaphragm contraction to sustain breathing during neuromuscular impairments. Wild type, C57/bl6 mice (n=10) received an intrapleural injection of an adeno-associated virus (AAV) construct containing the transgene for the light activated ion channel channelrhodopsin-2 (34 µl, AAV9-ACAGW-ChR2-mVenus, titer: 1.8x1013 vg/ml). After allowing 8-10 weeks for transgene expression, electromyography (EMG) and pneumotachography were measured during spontaneous breathing under isoflurane anesthesia. To test optogenetic activation, a high-power, 472 nm, micro-LED was directed at the inferior diaphragm surface. Stimulus pulse durations (PD) ranging from 0.1-1.0 ms and interpulse intervals (IPI) of 0.1, 0.5, 1.0, and 5.0 ms were tested. Directing light at the diaphragm evoked clearly discernable EMG activity in 10 of 10 animals treated with the AAV9 vector. The 5 ms IPI induced the largest EMG activation, occurring at a level comparable to endogenous diaphragm bursts. Stimulation with a 0.1 ms PD / 0.1 ms IPI, and 1 ms PD / 5 ms IPI both were able to generate robust increases in respiratory airflow. Optogenetic stimulation was repeated following an acute unilateral phrenic nerve section which abolished ipsilateral diaphragm EMG. The contralateral diaphragm inspiratory EMG signal was then used to “trigger” the light stimulation of the paralyzed hemi-diaphragm. This procedure enabled a robust, bilateral diaphragm activation in all mice that received the unilateral phrenicotomy (n= 5). Histology confirmed robust expression of mVenus in diaphragm myofibers in mice treated with the vector. Directing light at the diaphragm of non-AAV treated control mice caused no discernible impact on diaphragm EMG activity (n=2). We conclude that intrapleural AAV9-ACAGW-ChR2-mVenus injection effectively drives transgene expression in the diaphragm, and this approach can be used to enable robust optogenetic activation of this critically important respiratory muscle. To our knowledge, this is the first demonstration of light activation of the diaphragm, and this success opens up new directions for therapeutic targeting of diaphragm paralysis and respiratory insufficiency.

Observation of transition between multimode Q-switching and spatiotemporal mode locking

We report experimental observation of multimode Q -switching and spatiotemporal mode locking in a multimode fiber laser. A typical steady Q -switching state is achieved with a 1.88 μs pulse duration, a 70.14 kHz repetition rate, and a 215.8 mW output power, corresponding to the single pulse energy of 3.08 μJ. We find weak spatial filtering is essential to obtain stable Q -switched pulses, in contrast to the relatively stronger spatial filtering for spatiotemporal mode locking. Furthermore, a reversible transition process, as well as a critical bistable state, between multimode Q -switching and spatiotemporal mode locking, is achieved with specific spatial coupling and waveplates sets. We believe the results will not only contribute to understanding the complicated nonlinear dynamics in multimode, fiber-based platforms, but also benefit the development of promising high-pulse energy lasers.

Improvement of Microstructure and Wear resistance of X12 Tool Steel by Using Laser Surface Re-Melting Technique

Nd-YAG lasers have been successfully used in recent years as reliable heat source to surface modification of engineering materials such as laser surface re-melting. In the present study, X12 tool steel was surface modified by using pulse Nd-YAG laser technique. Laser parameters are selected of 12 J pulse energy, 15 Hz frequency, 20 mm defocus length, 6 ms pulse duration, and 5.6 mm /s mm scanning speed. These parameters were chosen after undertaking trials to give suitable parameters in this process. Optical microscopy and backscattered scanning electron microscopy (SEM) with EDS and X-ray diffraction techniques were used to analyse the microstructure changes of the surface of tool steel. Wear resistance test was achieved by using a pin on disk method. The reason for this work is to improve the wear resistance for surface layer of tool steel after changes the morphology of the structure by rapid solidification during laser re-melting. In general, the structure consists of the dendrite and cellular structures with δ ferrite formed under conditions of rapid solidification without the primary coarse carbides. After laser melting, the results of the structure at the surface layers show an increase in wear resistance.

Human Thoracolumbar Spine Tolerance to Injury and Mechanisms From Caudo-Cephalad Loading: A Parametric Modeling Study.

The aims of this investigation were to delineate the internal biomechanics of the spine under vertical impact vector and assess the probability of injury. Male and female whole-body human finite element models were used. The restrained occupants were positioned on the seat, and caudo-cephalad impacts were applied to the base. Different acceleration-time profiles (50-200 ms pulse durations, 11-46 g peak accelerations) were used as inputs in both models. The resulting stress-strain profiles in the cortical and cancellous bones were evaluated at different vertebral levels. Using the peak transmitted forces at the thoracolumbar disc level as the response variable, the probability of injury for the male spine was obtained from experimental risk curves for the various pulses. Results showed that the shorter pulse durations and rise times impart greater loading on the thoracolumbar spine. The analysis of von Mises stress and strain distributions showed that the compression-related fractures are multifaceted with contributions from both the cortical and cancellous bony components of the body. Profiles are provided in the paper. The intervertebral disc may be involved in the fracture mechanism, because it acts as a medium of load transfer between adjacent vertebrae. Injury risks for the shortest pulse was 63%, and for the widest pulse it was close to zero, and injury probabilities for other pulses are given. The present modeling study provides insights into the mechanisms of internal load transfer and describes injury risk levels from caudal to cephalad impacts.

Comparison of short-pulse subthreshold (532\xa0nm) and infrared micropulse (810\xa0nm) macular laser for diabetic macular edema

The purpose of the study was to assess both anatomic and functional outcomes between short-pulse continuous wavelength and infrared micropulse lasers in the treatment of DME. This was a prospective interventional study from tertiary care eye hospital—King Khaled Eye Specialist Hospital (Riyadh, Saudi Arabia). Patients with center-involving diabetic macular edema were treated with subthreshold laser therapy. Patients in the micropulse group were treated with the 810-nm diode micropulse scanning laser TxCell (IRIDEX Corporation, Mountain View, CA, USA) (subthreshold micropulse—STMP group). Laser was applied according to recommendations for MicroPulse (125 microns spot size, 300 ms pulse duration and power adjustment following barely visible testing burn) in a confluent mode (low intensity/high density) to the entire area of the macular edema. Patients in the short-pulse group were treated with grid pattern laser with 20 ms pulse PASCAL laser 532 nm (TopCon Medical Laser Systems, Tokyo, Japan) with EndPoint algorithm, which was either 30% or 50% of testing burn (EndPoint 30% and EndPoint 50% groups, respectively). Main outcome measures included best-corrected visual acuity (BCVA in logMAR) and foveal thickness at baseline and the last follow-up visit at 6 months. There were 44 eyes in the micropulse group, 54 eyes in the EndPoint 50% group and 18 eyes in the EndPoint 30% group. BCVA for the whole cohort (logMAR) was 0.451 (Snellen equivalent 20/56) at baseline, 0.495 (Snellen equivalent 20/62) (p = 0.053) at 3 months, and 0.494 (Snellen equivalent 20/62) at the last follow-up (p = 0.052). Foveal thickness for the whole cohort was 378.2 ± 51.7 microns at baseline, 347.2 ± 61.3 microns (p = 0.002) at 3 months, and 346.0 ± 24.6 microns at the final follow-up (p = 0.027). As such the short-pulse system yields more temporary reduction in edema. Comparison of BCVA between baseline and 6 months for EndPoint 30%, EndPoint 50% and STMP groups was p = 0.88, p = 0.76 and p = 0.003, respectively. Comparison of foveal thickness between baseline and 6 months for EndPoint 30%, EndPoint 50% and STMP groups was p = 0.38, p = 0.22 and p = 0.14, respectively. We conclude that the infrared micropulse system seems to improve functional outcomes. When applied according to previously published reports, short-pulse system may yield more temporary reduction in edema while infrared micropulse system may yield slightly better functional outcomes.

Application of Fractional Co2 Laser Modification of PEEK in Dental Implants, In vivo Study

This study aimed to Modify the PEEK surface using Fractional CO2 laser in different range of parametersto change the surface topography regarding roughness and wettability to enhance osseointegration. A PEEKblock (Ceramill PEEK 98X20 N -JUVORA dental innovations, UK) was used to prepare substrate. By CADCAM system, PEEK was cut into discs (2 mm thickness and 10 mm diameter). the discs were smoothed bysilicon carbide paper of 500 grit and a rotation motion, polishing machine at 200 rpm for one minute usedto polish the discs, finally cleaned with ethanol alcohol using ultrasonic cleaner. Different parameters weretested to study their effects on PEEK surface; therefore, several trails were done using Fractional CO2 laserdevice. Surfaces of the irradiated PEEK discs were examined microscopically at different magnificationpower. Then SEM was used. Then, PEEK samples were scanned by (EDS). Range of powers were used (2,4, 6, 8, 10, 12) W The distance between spots was 0.2mm and 0.2 ms pulse duration to ensure maximumcoverage of laser effect. The energy range was (4 - 25) which was n’t enough to produce any effect. To testthe effect of pulse duration different values were also studied starting from 0.2ms then increase the pulseduration. 0.4,0.6,0.8 ms to increase the energy per pulse accordingly. Starting from short pulse durationup to 0.6ms there was no effect even when the power increased. At 0.8 ms pulse duration, the effect wasrecognized on the specimen surface. The collected data of previous trials direct the operator to reduce pulseduration to have best criteria, including surface roughness, wettability, without carbonization or cracks.Conclusions: Successful modification of PEEK surface can be done with fractional CO2 laser. Laserparameters as power, pulse duration, distance between spotes and number of scans are key factors induceddifferent range of effect considering material’s properties.

Generation of particles and fragments by quasicontinuous wave fiber laser irradiation of stainless steel, alumina, and concrete materials

An experimental characterization is presented on fine particles, droplets, and fragments produced at the interaction region between a 2.7 kW quasicontinuous wave (repetitive pulsed operation with a 10 ms pulse duration) fiber laser and stainless steel, alumina, and heavy concrete samples. In the samples, the recoil pressure induced by vaporization pushes particles and fragments into the ambient atmosphere. In order to preserve a safe working environment, in particular for nuclear decommissioning, special care should be taken to confine and retrieve such particles during laser processing. In the experiments, particle production from the vapor and the molten phase layer in the targeted material was observed with a high-speed camera, with fine particles collected and analyzed using an electron microscope. The observed results were qualitatively interpreted with the help of a simplified one-dimensional hydrodynamic code coupled with a stress computation code. Characterization and classification of the results are expected to provide a useful database that will contribute to the decommissioning of nuclear facilities and other industrial applications.

Ultrasound and microbubbles (USMB) potentiated doxorubicin penetration and distribution in 3D breast tumour spheroids

Ultrasound and microbubbles (USMB) has been shown to improve chemotherapy in vitro cell suspension and monolayer models. These models are limited in their ability to study the potential of USMB in enhancing drug penetration within a three-dimensional (3D) tissue model which can in part reproduce the organization of a microtumour recapitulating cell-cell interactions and diffusion of molecules through the tissue. The 3D tumour spheroid models are considered as bridge for filling the gap between 2D in vitro monolayer cultured cells and animal models. In this study, we developed a 3D MDA-MB-231 breast cancer spheroid model and investigated the potential of USMB in enhancing drug penetration and distribution within the spheroid. The 3D spheroids were exposed to USMB (770 kPa Peak negative pressure, 1 MHz pulse frequency, 8 μs pulse duration and 2 m s pulse repetition period; and Definity at 1.7% v/v concentration) and doxorubicin (Dox) at 50 μM concentration. The short- and long-term effects on the spheroids were assessed using flow cytometry and Laser scanning confocal microscopy (LSCM). The application of USMB enhanced penetration of Dox into deeper regions of tumour spheroid. The Dox distribution was assessed using 3D optical sectioning and radial profiling at different z-planes of the spheroids. The flow cytometry data confirms that the USMB increases the Dox uptake per cell by 25% with 1.2 fold increase in total Dox fluorescence. No significant differences were observed in the long-term spheroid size with Dox + USMB compared to Dox alone. However, the spheroids appear more dispersed with the combined treatment of Dox + USMB compared to Dox alone. The tumour model show the enhanced chemotherapeutic effect in 3D tumour spheroids of USMB along with increased penetration and accumulation of chemotherapeutic molecules into deeper spheroid regions.

Treatment of Pain in Keloids Using Only a Long‐Pulsed 1064 nm Nd:YAG Laser

Keloids are benign lesions arising from overproduction of the extracellular matrix and abnormal collagen deposition by dermal fibroblasts. This altered wound healing typically occurs in response to dermal trauma. Keloid treatment poses a challenge due to the variable nature of treatment response, which can be affected by the size, appearance, and associated symptoms of erythema, pruritus, and pain. Recently, successful treatment of keloids has been reported using the Nd:YAG laser in conjunction with 5-fluorouracil and intralesional corticosteroids. We present a series of patients with symptomatic keloids, who we treated with only a 1064 nm Nd:YAG laser. Eight patients of Fitzpatrick skin types I-VI presented for treatment of keloids with associated symptoms of pain. The keloids were most commonly located on the trunk, and seven patients had intralesional steroid injections prior to presentation with persistence of symptoms. Patient treatment consisted of two passes under a long-pulsed 1064 nm Nd:YAG laser with a 10 mm spot size, a fluence of 18-19 J/cm2 , and 60 ms pulse duration every 3-8 weeks. Patient-reported pain scores were collected before and after treatment. Following treatment, transient erythema and mild edema were noted at the treatment site. All patients reported improvement in the symptoms of pain, with an average of a 5-point reduction using a 10-point scale (R: 2-10). Five out of eight patients had total resolution of their pain. An average of 3.25 treatments (R:1-5) were needed for patients to first notice an improvement in the pain. A Wilcoxon signed-rank test showed that treatment with a 1064 nm laser elicited a statistically significant improvement in pain in individuals with keloids (Z = 2.46, P = 0.01). No patients in our study suffered any scarring or pigment changes as a result of these treatments. Keloids are a common condition with variable rates of treatment satisfaction. Lasers have been used in an attempt to improve clinical appearance and associated symptoms. We report a significant reduction in pain for patients treated exclusively with a 1064 nm Nd:YAG laser. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

The effects of CO2 fractional laser on improving the scar of alar base incision in rhinoplasty patients

Objectivepost-surgical complications of rhinoplasty such as scars may alter the success rate of the operation. The aim of this study was to investigate the effects of fractional CO2 laser on the scars of alar base region in rhinoplasty patients. Materials and methodsTwenty six patients who had subsequent scar in the alar base region after open rhinoplasty were enrolled to this clinical study. Their skin type was recorded using Fitzpatrick scale, and then patients were randomly allocated into the control and the laser groups. Patients in the control group received no treatment, in the laser group, one session of fractional CO2 laser therapy with a 0.05 mm spot diameter, 4 ms pulse duration, 12−14 W power and 48_56 mJ energy in each pulse was completed. The scar score was evaluated using Vancouver Scar Scale before and 6 months after the treatment. The Scar score was calculated in a descriptive manner. Paired t-test and (Wilcoxon test) were employed to compare the results before and after the treatment. Data were analyzed using SPSS software version 22, and the level of significance was P < 0.05. ResultsNo difference was observed regarding the demographic information and the skin type between the two groups. After 6 months, reduction in the scar score was observed in both groups, however, the difference was not statistically significant. ConclusionThis study concluded that fractional CO2 laser did not affect the scar of alar base incision after rhinoplasty.

Displacement Imaging for Focused Ultrasound Peripheral Nerve Neuromodulation.

Focused ultrasound (FUS) is an emerging technique for neuromodulation due to its noninvasive application and high depth penetration. Recent studies have reported success in modulation of brain circuits, peripheral nerves, ion channels, and organ structures. In particular, neuromodulation of peripheral nerves and the underlying mechanisms remain comparatively unexplored in vivo. Lack of methodologies for FUS targeting and monitoring impede further research in in vivo studies. Thus, we developed a method that non-invasively measures nerve engagement, via tissue displacement, during FUS neuromodulation of in vivo nerves using simultaneous high frame-rate ultrasound imaging. Using this system, we can validate, in real-time, FUS targeting of the nerve and characterize subsequent compound muscle action potentials (CMAPs) elicited from sciatic nerve activation in mice using 0.5 to 5 ms pulse durations and 22 - 28 MPa peak positive stimulus pressures at 4 MHz. Interestingly, successful motor excitation from FUS neuromodulation required a minimum interframe nerve displacement of 18 μm without any displacement incurred at the skin or muscle levels. Moreover, CMAPs detected in mice monotonically increased with interframe nerve displacements within the range of 18 to 300 μm . Thus, correlation between nerve displacement and motor activation constitutes strong evidence FUS neuromodulation is driven by a mechanical effect given that tissue deflection is a result of highly focused acoustic radiation force.

Microshear Bond Strength of Composite Resin to Enamel Treated With Titanium Tetrafluoride and the Carbon Dioxide Laser (10.6 µm): An In Vitro Study.

Introduction: The present study aims to assess the microshear bond strength (µSBS) of composite to enamel treated with titanium tetrafluoride (TiF4 ) and CO2 laser irradiation. Methods: Fifteen human molars were sectioned and their enamel surfaces were abraded. The sections were randomly assigned to 5 groups (n=15): (CO); control group, (AP); treated with 1.23% acidulated phosphate fluoride (APF) for 4 minutes, (Ti); 4% TiF4 for 1 minute, (L+AP); CO2 laser irradiation (10.6 µm wavelength, 1 W peak power, 10 ms pulse duration, 500 ms repetition time, 0.2 mm beam spot size at the tissue level, 2 cm distance of handpiece tip to tissue surface (DSE, South Cores) followed by 1.23% APF, and (L+ Ti); 10.6μm CO2 laser irradiation followed by 4% TiF4 for one minute. Using Tygon tubes, Z250 (3M/ESPE) composite was bonded to the surface of the samples. The µSBS of composite to enamel was measured using a microtensile testing machine after 500 thermal cycles. The data were analyzed by one-way ANOVA and the Tukey HSD test (P <0.05). Results: The mean µSBS was 20.66, 20.21, 13.44, 23.01, and 10.16 MPa in CO, AP, Ti, L+AP, and L+Ti groups respectively. Significant differences were observed between CO and Ti (P =0.026) and also CO and L+ Ti (P <0.0001). Conclusion: The application of TiF4 per se and after CO2 laser irradiation on enamel decreased the µSBS of composite to enamel; on the other hand, APF alone and after laser irradiation did not have any adverse effect on the µSBS of composite to enamel.

Clinical Evaluation of Individualized and Navigated Microsecond Pulsing Laser for Acute Central Serous Chorioretinopathy.

A computational model has predicted parameters for using a navigated microsecond pulsing laser system to treat central serous chorioretinopathy (CSC). A prospective, single-center, interventional case series was conducted for patients with acute CSC who were enrolled following screening and informed consent. Treatment involved laser pulse duration of 50 μs, 2.4% Duty Cycle, 100 μm spot size, and 10 ms pulse duration. Average best-corrected visual acuity (decimal) of 12 patients improved from 0.86 ± 0.03 at baseline to 0.97 ± 0.01 at 3 months. Baseline central retinal thickness decreased from 452.58 μm ± 24.53 μm at baseline to 249.25 μm ± 2.92 μm at 3 months. Retinal sensitivity improved from 24.1 dB ± 1.09 dB at baseline to 28.98 dB ± 0.23 dB at 3 months. In all cases, subretinal fluid was resorbed. The parameter sets derived from the computer model can be applied safely and effectively for CSC treatment using the navigated microsecond pulsing laser system. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:512-520.].

Micro-structured tungsten, a high heat flux pulse proof material

Abstract Micro structured tungsten is a new approach to address one of the main issues of tungsten as high heat flux (HHF) plasma facing material (PFM), which is its brittleness and its propensity to crack formation under pulsed, ELM like, heat loads (Loewenhoff et al., 2015; Wirtzet al., 2015 [2,3]). With power densities between 100 MW/m2 and 1 GW/m2, progressive thermal fatigue induced damages like roughening, subsequent cracking and even melting will occur in dependence on the pulse number and PFM base temperature. This represents a serious issue for the usage of tungsten as HHF-PFM. In future tokamaks, such as ITER, about 108 ELMs are expected to occur during the operational lifetime. Several approaches have been tried to overcome this brittleness issue, e.g. alloying tungsten with others elements (Linsmeier et al., 2017 [4]) or introducing pseudo-ductility due to the additions of fibres thus creating composites (Reiser et al., 2017 [5]). Micro-structured tungsten showed a significant improvement in comparison with any of these approaches with respect to the damage expected by ELMs. This investigation on both bulk reference and micro-structured tungsten was performed in the PSI-2 facility (Kreter et al., 2015 [8]). A sequential load was applied combining steady state deuterium plasma (5.1 × 1025 D + m−2, 51 eV, 240 °C, 150 min) loading with laser pulses (up to 105 pulses of 0.5 GW/m2, 3.6 mm spot diameter, 20 J, 1 ms pulse duration, up to 25 Hz pulse frequency). In contrast to reference bulk tungsten, none of the applied loading conditions caused any evident damage on the micro-structured tungsten. The maximum surface temperature within the loaded area measured with a fast pyrometer was increased by about 800 °C at the end of the laser exposure for the reference sample. This is related to the emissivity changes and local temperature increase caused by surface degradation. Meanwhile, the micro-structured sample did not show any change of its temperature response from the 10th to the 100 000th pulse.