Laser Power Settings Research Articles

Directed energy deposition of Ti6Al4V wire with continuous layer varied laser power

The laser-based directed energy deposition (DED) additive manufacturing enables the efficient fabrication of metallic parts. The layer-wise performance in DED-built metallic parts is challenging to remain consistent due to the intricate heat accumulation. As such, it is of significance to control the printing quality by adjusting the process settings with layers. In this work, we used DED to achieve Ti6Al4V wire deposition with continuously layer-varied laser power. Three laser power settings were selected to investigate the variation in defects, microstructure, and mechanical properties with layers. Our findings suggested that optimizing real-time laser power is critical for achieving desirable manufacturing efficiency and resultant performance in the DED of metallic materials. This research provides valuable guidelines for parameter optimization in DED processes, aiming to enhance the production quality and performance of high-strength metallic components, particularly in sectors demanding high-performance materials.

Frequency of retinal detachments in dogs after prophylactic transpupillary retinopexy.

To evaluate the frequency of retinal detachments following prophylactic transpupillary retinopexy (PTPRP). The medical records of dogs that received a PTPRP between 2014 and 2022 were retrospectively analyzed for age, sex, breed, reason for retinopexy, laser power setting, number of retinal burns, follow-up duration, and outcome. Laser power settings were increased until retinal burns could be visualized and were made 360° in a double row in the peripheral retina. Fifty-seven cases (75 eyes), 28 males and 29 females, had PTPRP performed. The median age was 8 years (4 months-14 years) with Shih tzu (n = 12), Bichon (n = 5), Miniature Poodle (n = 5), and Yorkie (n = 4) being the most common breeds. PTPRP were performed due to severe vitreal degeneration (n = 66), retinal detachment in the contralateral eye (n = 25), capsular tear with escaped lens material during phacoemulsification (n = 6), intracapsular lens extraction (n = 2), and lens luxation during phacoemulsification (n = 3). The median power setting, number of retinal burns, and follow-up time were 300 mW (201-595 mW), 210 burns (35-921 burns), and 473 days (14-1862 days), respectively. Additionally, five patients had a barrier-pexy performed in the contralateral eye, due to partial detachment. Retinal detachment occurred in 3/75 (4.0%) of eyes that received a PTPRP at the final examination. Of the patients with a detachment in the contralateral eye (n = 25), no detachment was noted at the last follow-up examination. Two partial detachments that had barrier-pexies had progressed at the final examination. These results demonstrate that PTPRP may be beneficial in decreasing the risk of retinal detachment in selected cases.

Monitoring Intrarenal temperature changes during Ho: YAG laser lithotripsy in patients undergoing retrograde intrarenal surgery: a novel pilot study.

Ho: YAG laser lithotripsy is widely used for urinary stone treatment, but concerns persist regarding its thermal effects on renal tissues. This study aimed to monitor intrarenal temperature changes during kidney stone treatment using retrograde intrarenal surgery with Ho: YAG laser. Fifteen patients were enrolled. Various laser power settings (0.8J/10 Hz, 1.2J/12 Hz) and irrigation modes (10cc/min, 15cc/min, 20cc/min, gravity irrigation, and manual pump irrigation) were used. A sterile thermal probe was attached to a flexible ureterorenoscope and delivered into the calyceal system via the ureteral access sheath. Temperature changes were recorded with a T-type thermal probe with ± 0.1°C accuracy. Laser power significantly influenced mean temperature, with a 4.981°C difference between 14W and 8W laser power (p < 0.001). The mean temperature was 2.075°C higher with gravity irrigation and 2.828°C lower with manual pump irrigation (p = 0.038 and p = 0.005, respectively). Body mass index, laser power, irrigation model, and operator duty cycle explained 49.5% of mean temperature variability (Adj. R2 = 0.495). Laser power and operator duty cycle positively impacted mean temperature, while body mass index and specific irrigation models affected it negatively. Laser power and irrigation rate are critical for intrarenal temperature during Ho: YAG laser lithotripsy. Optimal settings and irrigation strategies are vital for minimizing thermal injury risk. This study underscores the need for ongoing research to understand and mitigate thermal effects during laser lithotripsy.

Numerical simulation of free-surface evolution in laser polishing of 100 Cr6 bearing steel

Abstract This research focuses on the laser surface polishing process of 100 Cr6, employing a moving Gaussian heat source. It establishes a two-dimensional transient model for laser polishing, taking into account the integrated effects of fluid flow and temperature fields, as well as the combined influence of capillary and thermocapillary forces. The model was used to perform numerical simulations to study the evolution of surface morphology during the laser polishing process. The investigation specifically examines how laser power and scanning speed influence the quality of the polishing outcome. The results demonstrate that an optimal surface roughness of approximately 0.571 μm is attained at a laser power setting of 200 W and a scanning speed of 300 mm/s.

Surface microstructure and corrosion characterization of AZ31 magnesium alloys fabricated by laser surface-modification

This study aimed to improve the corrosion resistance of Mg alloys, and to this end, AZ31 Mg alloy was subjected to laser surface re-melting using a fiber laser. Subsequently, a comparative analysis was conducted on the microstructures of the re-melted surfaces under various laser power settings, and the influence of laser surface re-melting on corrosion characteristics was investigated through a potentiodynamic polarization test. The test results show that laser surface re-melting produced a distinct reduction in the crystallite size of magnesium, ranging from 11.23–15.80 μm within the laser-melted layers. The maximum melted layer thickness of 820 μm was achieved with a laser power of 2100 W. The process of laser surface re-melting notably heightened the hardness, particularly as the power increased, which was attributed to swift solidification. The most noteworthy hardness measurement of 92.1 HV0.02 was recorded at 2100 W. Thus, the study shows that laser surface re-melting significantly enhances the corrosion resistance of Mg alloys, primarily owing to the formation of a corrosion product. The smaller grain size on the surface contributes to the formation of a dense product film.

Investigation of Deposition Parameters for Near-Beta Alloy Ti-55511 Fabricated by Directed Energy Deposition

The directed energy deposition (DED) parameters were determined for near-β alloy Ti-55511 by employing statistical design of experiments (DOEs) methods. Parameters resulting in fully dense freeform deposits were identified using two sequential DOEs. Single laser tracks were printed with several laser power, traverse rate, and powder feed rate settings in an initial DOE to identify promising build parameters. The capture efficiency and effective deposition rate were used to characterize and rank the single track deposits. The best parameters were then used to print a solid cube with various X–Y and Z overlaps (different hatch spacing, HS, and layer thickness, ZS) in a second DOE. Suitable deposition parameters were selected based on the cube density and microstructure and were used to fabricate larger tensile samples for mechanical testing. Multiple parameter sets were found to provide dense Ti-55511 deposits with acceptable mechanical properties and the parametric models showed statistical significance.

Endoscopic Conservative Treatment of Upper Urinary Tract Urothelial Carcinoma with a Thulium Laser: A Systematic Review.

Thulium lasers (TLs), namely the Thulium fiber laser (TFL) and the Thulium:YAG (Tm:YAG), are being increasingly adopted for the conservative treatment of upper urinary tract urothelial carcinoma (UTUC). However, to date, the real clinical impact of TLs on UTUC management remains not well-characterized. We performed a review of the literature to summarize the current evidence on TLs for UTUC treatment. We performed a systematic review in January 2023 using the Embase and Medline online databases, according to the PRISMA recommendations and using the PICO criteria. Outcomes of interest were: (i) to assess the safety and feasibility of TLs in the treatment of UTUC, and (ii) to evaluate the oncological outcomes in terms of tumor recurrence and conservative treatment failure. Moreover, we described TL characteristics and its interaction with soft tissue. a total of 458 articles were screened, and six full texts including 273 patients were identified. All the included studies were retrospective series. Mean patient age ranged from 66 to 73 years. The indication of a conservative treatment was elective and imperative in 21.7-85% and 15-76% of cases, respectively. Laser power settings varied from 5 to 50 W. No intraoperative complications were reported, and all the procedures were successfully performed. The tumor recurrence rate was 17.7-44%, and the indication to radical nephroureterectomy was 3.7-44% during a follow-up of 6-50 months. Most of the postoperative complications were mild and transient, and ureteral strictures were reported in two studies. Major limitations were the retrospective nature of the studies, the small sample sizes, and the short follow-up. TL is an effective and safe technology for endoscopic UTUC treatment. However, current available literature lacks prospective and multicentric studies with large population sizes and long-term follow-up.

Numerical investigation of balling defects in laser-based powder bed fusion of metals with Inconel 718

Balling is one of the main single melt track defects limiting stable production of dense parts with laser-based powder bed fusion of metals (PBF-LB/M) additive manufacturing. A fundamental understanding of balling therefore is critical for process control and optimization. Violent interface dynamics present a severe challenge for mesh-based numerical schemes, and can be dealt with by particle methods. In this study, we focus on investigating single melt tracks by smoothed particle hydrodynamics (SPH). The considered regime is characterized by long liquid melt pools and remelting of the previous layer. The balling mechanism is driven by Marangoni and capillary forces. The resulting convective melt flux leads to the accumulation of melt in the tail region and leaves an exposed area of marginal layer build-up. In addition to the competing mechanisms of solidification and spreading, a competition between spreading and melt contraction shortly after the melt pinch-off is observed. We find a similar balling behavior yet different ball size at different laser power settings. We stress that SPH with accurate interface modeling has the capability to quantify balling processes and to improve the understanding of balling mechanisms.

Intertwin Membrane Perforation and Umbilical Cord Entanglement after Laser Surgery for Twin-Twin Transfusion Syndrome: Prevalence, Risk Factors, and Outcome

Introduction: Perforation of the intertwin membrane can occur as a complication of fetoscopic laser surgery for twin-twin transfusion syndrome (TTTS). Data on the occurrence and the risk of subsequent cord entanglement are limited. The objective of this study was to assess the prevalence, risk factors and outcome of intertwin membrane perforation, and cord entanglement after laser surgery for TTTS. Methods: In this multicenter retrospective study, we included all TTTS pregnancies treated with laser surgery in two fetal therapy centers, Shanghai (China) and Leiden (the Netherlands) between 2002 and 2020. We evaluated the occurrence of intertwin membrane perforation and cord entanglement after laser, based on routine fortnightly ultrasound examination and investigated the risk factors and the association with adverse short- and long-term outcomes. Results: Perforation of the intertwin membrane occurred in 118 (16%) of the 761 TTTS pregnancies treated with laser surgery and was followed by cord entanglement in 21% (25/118). Perforation of the intertwin membrane was associated with higher laser power settings, 45.8 Watt versus 42.2 Watt (p = 0.029) and a second fetal surgery procedure 17% versus 6% (p < 0.001). The group with intertwin membrane perforation had a higher rate of caesarean section (77% vs. 31%, p < 0.001) and a lower gestational age at birth (30.7 vs. 33.3 weeks of gestation, p < 0.001) compared to the group with an intact intertwin membrane. Severe cerebral injury occurred more often in the group with intertwin membrane perforation, 9% (17/185) versus 5% (42/930), respectively (p = 0.019). Neurodevelopmental outcome at 2 years of age was similar between the groups with and without perforation of the intertwin membrane and between the subgroups with and without cord entanglement. Conclusion: Perforation of the intertwin membrane after laser occurred in 16% of TTTS cases treated with laser and led to cord entanglement in at least 1 in 5 cases. Intertwin membrane perforation was associated with a lower gestational age at birth and a higher rate of severe cerebral injury in surviving neonates.

Synthesis of PEG-PPG-PEG templated polydopamine nanoparticles under intensified conditions: Kinetics investigation, continuous process design and demonstration for photothermal application

Polydopamine is a nature inspired functional material with promising applications in a plethora of fields due to its structural, chemical, and optical properties. While there is significant interest in the preparation of polydopamine based nanomaterials that take advantage of its properties, less attention has been given to the optimisation of the synthetic process, which typically involves the oxidative self-polymerisation of dopamine under basic pH and requires 24–72 h for reaction completion. The present work investigated the kinetics of polydopamine formation in the presence of Pluronic P-123 (PEG-PPG-PEG) micelles acting as a soft template, in low monomer concentrations (that promote particle growth instead of nucleation) as a function of temperature and pressure. Simultaneous increase of pressure and temperature (up to 50 °C and 5 bar O2) was found to significantly reduce the reaction time to 20–40 min without compromising the particle quality. Based on the results of the kinetic investigation, the polydopamine synthesis was translated into a continuous process utilising a millifluidic co-axial membrane reactor with a focus on ease of use, process conditions’ reproducibility and safety of operation. The reactor produced nanoparticles similar to the batch synthesis and resisted fouling (which is generally expected in a compact flow reactor) due to the action of the P-123 surfactant. Due to the nontoxic process that utilises only biocompatible materials and oxygen as the oxidising agent, and the melanin-like structure of polydopamine, photothermal heating of the synthesised nanoparticles under concentrated IR irradiation at 808 nm light was studied, as this can potentially be used for photo-induced hyperthermia. The hyperthermia threshold of 10 °C temperature increase at relatively low laser power settings (fluence 1.77 W/cm2) was achieved, making it a promising candidate for this application.

The safest power to be applied in relation to diameter of the vein to give maximal benefit with least complications in endovenous laser ablation of varicose veins

Background Over the years, there have been significant advancements in the treatment of varicose veins. In most surgical settings, the open procedure is still the primary approach. Yet, the popularity of less invasive procedures like EVLA and RFA has produced fantastic outcomes. Objective to assess the safest power of laser which gives maximal effect and least complications in ablation of varicose veins. Methodology A prospective observational study inducing EVLA of different laser power settings (7W &amp; 10W) with preoperative assessment then follow up by CEAP &amp; VCSS and duplex ultrasound measuring great saphenous vein (GSV) diameter and also post-operative complications and time to return to work. Results This study included 50 patients (52 limbs). The Patients were distributed as regard laser power used into two groups (7W, 10W) of 26 limbs for each one. As regard GSV measures changes, there was highly statistically significant decrease in GSV diameter after 1 m and after 3 m compared to preoperative, with P value P&lt;0.001, among patients group. Also, there is higher number of cases with GSV&gt;10 mm in power of laser ‘10w’ group compared to ‘7w; group, with P value (P&lt;0.001); while there is no statistically significant difference between power of laser 7w versus 10w, because all patients ≤10 mm after 1 month and after 3 months, with P value &gt;0.05.Statistically there was no significant difference between 7W &amp; 10W groups as regards time to return to work, CEAP scores and postoperative complications except the significant difference in Pain over the treated vein being less in 7W laser power group. Conclusion For endovenous laser ablation of varicose veins, both 7W and 10W laser power are indicated. They are risk-free and provide the greatest impact with the fewest difficulties for the chosen vein diameter. In our investigation, we came to the conclusion that patients with small GSV diameter required low laser power (7W), while those with large GSV diameter required high laser power (10W).

MP68-17 IN-VIVO THERMAL SAFETY VALIDATION OF URETEROSCOPY LASER POWER – IRRIGATION RATE PARAMETER PAIRS

You have accessJournal of UrologyCME1 Apr 2023MP68-17 IN-VIVO THERMAL SAFETY VALIDATION OF URETEROSCOPY LASER POWER – IRRIGATION RATE PARAMETER PAIRS Ron Marom, Julie J. Dau, Khurshid R. Ghani, Timothy L. Hall, and William W. Roberts Ron MaromRon Marom More articles by this author , Julie J. DauJulie J. Dau More articles by this author , Khurshid R. GhaniKhurshid R. Ghani More articles by this author , Timothy L. HallTimothy L. Hall More articles by this author , and William W. RobertsWilliam W. Roberts More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003331.17AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: High-power laser lithotripsy settings improve stone ablation rate and treatment efficiency but also can induce elevated fluid temperatures to a point of toxic thermal dose. Previous in-vitro work mapped out safety boundaries based on laser power/irrigation rate pairs. Our objective in this study was to assess the thermal safety of a range of laser power settings at different irrigation rates in an in-vivo model. METHODS: Ureteroscopy was performed in an anesthetized in-vivo porcine model with a novel prototype ureteroscope containing a thermocouple sensor at its tip. The distal end of the ureteroscope was positioned in the middle of a small calyx and maintained there for the entire experiment. Three trials of 60 seconds laser activation were carried out at each selected power setting and irrigation rate. Using MATLAB, thermal dose was calculated from the time-temperature curves for each trial using the Sapareto and Dewey formula. The threshold of thermal tissue injury was considered to be 120 equivalent minutes. Laser power-irrigation rate parameter pairs were categorized based on number of trials that exceeded thermal dose and designated in the figure as red (Unsafe) – all trials exceeded threshold, yellow – some trials exceeded threshold, green (Safe) – no trials exceeded threshold. RESULTS: The collecting fluid temperature was increased with greater laser power and slower irrigation rate. The calculated thermal dose was above threshold for the power setting of 17.5 Watts and irrigation flow rate of 9 ml/min. With irrigation flow rates greater than 24 ml/min, none of the tested laser power settings (up to 48 Watts) exceeded the thermal dose threshold from 60 seconds of continuous laser activation. CONCLUSIONS: This study demonstrates a method to assess thermal safety of laser power-irrigation rate parameter pairs in an in-vivo porcine model. Building upon this foundation, other variables such as operator duty cycle and pedal activation time can be incorporated to more accurately replicate real-world patterns of clinical laser user. Additionally, the impact of mitigation strategies (higher irrigation flow rates, control of laser operator duty-cycle, limiting pedal activation time and use of chilled irrigation fluid) can be assessed with these standardized methods. Source of Funding: Boston Scientific © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e960 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ron Marom More articles by this author Julie J. Dau More articles by this author Khurshid R. Ghani More articles by this author Timothy L. Hall More articles by this author William W. Roberts More articles by this author Expand All Advertisement PDF downloadLoading ...

MP05-15 PHOTONIC LITHOTRIPSY: EFFECT OF GOLD AND CARBON BASED NANOMATERIALS ON STONE COMMINUTION

You have accessJournal of UrologyCME1 Apr 2023MP05-15 PHOTONIC LITHOTRIPSY: EFFECT OF GOLD AND CARBON BASED NANOMATERIALS ON STONE COMMINUTION Ian Houlihan, Benjamin Kang, Smita De, and Vijay Krishna Ian HoulihanIan Houlihan More articles by this author , Benjamin KangBenjamin Kang More articles by this author , Smita DeSmita De More articles by this author , and Vijay KrishnaVijay Krishna More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003216.15AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Kidney stones affect ∼10% of individuals in the USA. The most common surgical stone treatments include laser lithotripsy by ureteroscopy and extracorporeal shock wave lithotripsy. Photonic lithotripsy (PL) is a novel technology for minimally-invasive, non-contact kidney stone treatment. PL utilizes photonic nanomaterials that convert low-intensity (<5 W), near-infrared laser energy to photothermal and/or photoacoustic energy for kidney stone fragmentation. Herein we investigate the effect of different photonic nanomaterials on PL. METHODS: Human kidney stones with a size range of 2–4 mm and a composition of >70% calcium oxalate (CaOx) were obtained from the Cleveland Clinic Pathology Lab. Five different photonic nanomaterials were evaluated: gold nanoshells (AuNS), gold nanorods (AuNR), multi-walled carbon nanotubes (MWNT), graphene oxide (GO), and polyhydroxy fullerenes (PHF). Each nanomaterial at each laser wavelength and power setting was tested with n=10 stones. Stones were treated with photonic nanomaterials and exposed to a NIR laser (785 nm or 1320 nm) at a distance of 10 mm for three, 3-minute intervals. Multiple intervals were used to observe changes and re-expose stones to the nanomaterial solution. The treatments were considered successful if two or more fragments were produced. RESULTS: Stones predominantly CaOx based were successively fragmented using the different nanomaterials (Figure 1) when irradiated with the 1320 nm and 785 nm NIR lasers. The 1320 nm laser successfully broke >50% of stones across all nanomaterials at 4 W and >30% of stones at 3 W. The 785 nm laser successfully broke >80% of stones across all nanomaterials at 2 W. No stones were fragmented at 1 W as not enough energy was generated for failure to occur. The stones analyzed pre and post PL by FTIR and µCT showed evidence of crack formation and thermal degradation. CONCLUSIONS: Photonic nanomaterials can fragment stones using laser wavelengths that are minimally absorbed by kidney tissue, at low energy and in non-contact mode at a distance of 10 mm. Successful stone comminution with different nanomaterials is dependent upon laser wavelength and laser power. All tested nanomaterials have the ability to fragment kidney stones in an in vitro setting. Source of Funding: LRI Accelerator Grant, Cleveland Clinic Caregiver Catalyst Award, U2Csupport 1U2CDK129440 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e49 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ian Houlihan More articles by this author Benjamin Kang More articles by this author Smita De More articles by this author Vijay Krishna More articles by this author Expand All Advertisement PDF downloadLoading ...

Er:YAG Laser Debonding of Lithium Disilicate Laminate Veneers: Effect of Laser Power Settings and Veneer Thickness on The Debonding Time and Pulpal Temperature.

Introduction: Er:YAG laser is a non-destructive tool for debonding of laminate veneers. This study investigated the effect of different laser powers on the pulp temperature and the time required to perform the debonding of lithium disilicate laminate veneers with different thicknesses. Methods: The labial enamel of 48 maxillary central incisors was flattened and polished. The teeth were restored with flat lithium disilicate ceramic veneers (4.0 mm×6.0 mm) with one of two different thicknesses (0.5 and 1.0 mm). Veneer debonding was performed with an Er:YAG laser with a wavelength of 2940 nm, pulse duration of 100 μm (VSP mode), 10 Hz, and one of the three laser power settings: 1.5 W (150 mJ), 3.0 W (300 mJ). and 5.4 W (540 mJ) (n=8). Veneer detachment time and intra-pulp temperature change (ΔT) were measured. Statistical analysis was performed using the two-way ANOVA and Bonferroni's post hoc test (α=0.05). The correlation between debonding time and temperature change was calculated using Pearson's correlation. Results: The longest time was recorded to remove the 1.0-mm veneer at 1.5 W (P<0.05) and the shortest time was recorded when deboning the 0.5 mm veneer with 5.4 W (P<0.05). ΔT decreased significantly with increasing laser power. A low correlation was found between time and ΔT (R2=0.113). Conclusion: Laser power and veneer thickness are important factors for veneer debonding; thinner veneers are removed faster. When debonding thick veneers, 5.4W laser power is more efficient and causes fewer changes to the pulp temperature.

The influence of beam focus during laser powder bed fusion of a high reflectivity aluminium alloy — AlSi10Mg

LPBF of Al alloys is associated with numerous challenges when compared to other commonly used alloys due to their higher reflectivity and thermal conductivity. In this work, processing diagrams, temperature prediction models, XCT, and metallography are used for establishing criteria in process parameter optimization of high reflectivity Al alloys based on AlSi$_{10}$Mg response in using 57 different process parameter combinations - 21 using a focused Gaussian laser beam and 36 using divergent beams. For LPBF systems with focused beam diameters <100 {\mu}m, divergent beams obtained by defocusing to a position above the LPBF build plate primarily lead to conduction mode melt pools, while a focused beam leads to transition and keyhole mode melt pools. Conduction mode melting helps in avoiding keyhole mode defects, resulting in parts with densities >99.98%. Additionally, an analytical model-guided selection of laser power and velocity settings for a focused beam help in stabilizing melt pool and spatter dynamics in the transition melting mode thereby enabling a potential to obtain density values close to conduction mode densities (~99.98%). A dimensionless keyhole number (Ke) was derived in this work to identify distinct regions of conduction (Ke of 0-12), transition (Ke of 12-20), and keyhole (Ke > 20) mode melting during LPBF of AlSi$_{10}$. A melt pool aspect ratio (ratio of melt pool depth to width) of ~0.4 is observed to be the threshold between conduction and transition/keyhole mode melt pools for AlSi$_{10}$, different from the conventionally assumed 0.5. Lastly, inferred laser absorptivity values (from experimental melt pools) of transition/keyhole mode melt pools are observed to be >40% higher when compared to conduction mode melt pools. This work demonstrates a dimensionless-process map method to obtain near fully dense parts that can be generalized for LPBF of high reflectivity alloys.

Characterization of Fluid Dynamics and Temperature Profiles During Ureteroscopy with Laser Activation in a Model Ureter.

Introduction: Ureteral thermal injury has been reported in patients following ureteroscopy with laser lithotripsy due to overheating of fluid within the ureter. Proper understanding of this risk necessitates knowing the volume of fluid available to absorb laser energy. This can be approximated as the volume of fluid that mixes during laser activation, since energy transfer through fluid is dominated by convection. Objectives of this study were to determine the volume of fluid that mixes during laser activation at different irrigation rates and to characterize the temporal/spatial temperature distribution in a model ureter. Methods: The model ureter consisted of a plastic tube-160 mm length and 5.3 mm inner diameter. Irrigation was first applied with clear, then dyed, deionized water at rates from 8 to 40 mL/min. The laser was activated at 20 W (0.5 J/40 Hz). The distances the dyed fluid propagated were measured and volumes calculated. Temperatures were recorded from six thermocouples-five embedded within the tube and one affixed to the ureteroscope. Thermal dose was calculated using the Dewey and Sapareto methodology. Results: The volume of total fluid mixing in the model ureter was ≤1.26 ± 0.10 cm3, consistent with a sharp temperature increase after laser activation from -5 to 25 mm from the ureteroscope tip. With irrigation rates ≤12 mL/min, calculated thermal dose within the model ureter exceeded the threshold of tissue injury and extended greater distances along the ureter with lower irrigation rates. Conclusion: The volume of total fluid mixing within the model ureter was found to be small thus conferring a greater risk of ureteral thermal injury. A thermocouple positioned near the tip of the ureteroscope reasonably approximates temperature in front of the ureteroscope. Until temperature sensors are incorporated into ureteroscopic systems, laser power settings should be carefully selected to minimize risk of ureteral thermal injury.

A method for reducing thermal injury during the ureteroscopic holmium laser lithotripsy

ObjectiveMany studies have demonstrated the heat effect from the holmium laser lithotripsy can cause persistent thermal injury to the ureter. The purpose of this study was to elucidate the use of a modified ureteral catheter with appropriate firing and irrigation to reduce the thermal injury to the “ureter” during the ureteroscopic holmium laser lithotripsy in vitro. MethodsAn in vitro lithotripsy was performed using a modified catheter (5 Fr) as the entrance for the irrigation and the holmium laser fiber while using the remaining space in the ureteroscopic channel as an outlet. Different laser power settings (10 W, 20 W, and 30 W) with various firing times (3 s, 5 s, and 10 s) and rates of irrigation (15 mL/min, 20 mL/min, and 30 mL/min) were applied in the experiment. Temperature changes in the “ureter” were recorded with a thermometer during and after the lithotripsy. ResultsDuring the lithotripsy, the local highest mean temperature was 60.3 °C and the lowest mean temperature was 26.7 °C. When the power was set to 10 w, the temperature was maintained below 43 °C regardless of laser firing time or irrigation flow. Regardless of the power or firing time selected, the temperature was below 43 °C at the rate of 30 mL/min. There was a significant difference in temperature decrease when continuous 3 s drainage after continuous firing (3 s, 5 s, or 10 s) compared to with not drainage (p<0.05) except for two conditions of 0.5 J×20 Hz, 30 mL/min, firing 5 s, and 1.0 J×10 Hz, 30 mL/min, firing 5 s. ConclusionOur modified catheter with timely drainage reducing hot irrigation may significantly reduce the local thermal injury effect, especially along with the special interrupted-time firing setting during the simulated holmium laser procedure.

Adding Value to Maple (Acer pseudoplatanus) Wood Furniture Surfaces by Different Methods of Transposing Motifs from Textile Heritage

The present paper is part of an ongoing research project carried out to find methods to transpose traditional motifs from Romanian textile heritage to furniture ornamentation, as an additional method of preserving the motifs besides conventional conservation. Modern technology, such as Computer Numerical Control (CNC) routing or laser engraving can revive furniture ornamentation, eliminating manual labor and long execution time. Three methods were applied to transpose a bicolored motif from a traditional Romanian blouse from Transylvania onto the surface of maple wood furniture. The first method utilized was nitrogen laser engraving, in which ten power settings between 10 W and 150 W were applied and color measurements were carried out on the resulting engraved surfaces. Following the International Commission on Illumination (CIELab) system analysis, two laser power settings were selected to engrave the ornament on a maple wood surface for an accurate reproduction. The second method employed a staining solution applied on flat wood surface, followed by routing the model on a CNC machine and further coating with lacquer. The third method consisted of CNC routing the model on the wood surface, then coloring the engraved ornament followed by surface sanding to remove color from the flat wood surface and, finally, lacquering. The ornaments transposed onto maple wood surfaces were aesthetically assessed, the technologies were analyzed, and the details of the processed ornaments were highlighted by Stereo Microscope investigation. The conclusions showed that each method adds value to the wood surface by original ornamentation and can be applied as furniture decoration.

Does the Novel Thulium Fiber Laser Have a Higher Risk of Urothelial Thermal Injury than the Conventional Holmium Laser in an In Vitro Study?

Introduction and Objective: The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the holmium:YAG laser (HL). However, some evidence suggests that the TFL generates more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during ureteroscopic laser lithotripsy in a benchtop model. Methods: A 1-cm BegoStone was manually impacted in the proximal ureter of a three-dimensional printed kidney-ureter model and submerged in 35.5°C saline. Lithotripsy was performed using a 7.6F flexible ureteroscope and a 200 μm laser fiber without a ureteral access sheath. The Dornier 30 W HL, Olympus 100 W HL, and Olympus 60 W TFL were compared. A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35 cc/minute at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. Five trials were performed for each of four different power settings: 3.6, 10, 20, and 30 W. Analysis of variance and Mann-Whitney U tests were performed with p < 0.05 considered significant. Results: Intraureteral fluid temperature increased as laser power settings increased for all lasers (p < 0.05). The TFL generated higher average ureteral fluid temperatures than the Dornier and Empower HL at all power settings tested (p < 0.001). The maximum temperature for the TFL was higher than the Dornier and Empower HL at all power settings tested (p < 0.001), except at 20 W with the Empower HL. At 30 W, the TFL exceeded 43°C, the threshold for tissue damage. Conclusions: The TFL generated more heat at all settings tested. Supraphysiologic ureteral temperatures may be generated with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both lasers could help improve the safety of ureteroscopic laser lithotripsy.

On the Fabrication of Defect-Free Nickel-Rich Nickel–Titanium Parts Using Laser Powder Bed Fusion

Abstract Laser powder bed fusion (L-PBF) additive manufacturing (AM) is an effective method of fabricating nickel–titanium (NiTi) shape memory alloys (SMAs) with complex geometries, unique functional properties, and tailored material compositions. However, with the increase of Ni content in NiTi powder feedstock, the ability to produce high-quality parts is notably reduced due to the emergence of macroscopic defects such as warpage, elevated edge/corner, delamination, and excessive surface roughness. This study explores the printability of a nickel-rich NiTi powder, where printability refers to the ability to fabricate macro-defect-free parts. Specifically, single track experiments were first conducted to select key processing parameter settings for cubic specimen fabrication. Machine learning classification techniques were implemented to predict the printable space. The reliability of the predicted printable space was verified by further cubic specimens fabrication, and the relationship between processing parameters and potential macro-defect modes was investigated. Results indicated that laser power was critical to the printability of high Ni content NiTi powder. In the low laser power setting (P &amp;lt; 100 W), the printable space was relatively wider with delamination as the main macro-defect mode. In the sub-high laser power condition (100 W ≤ P ≤ 200 W), the printable space was narrowed to a low hatch spacing region with macro-defects of warpage, elevated edge/corner, and delamination happened at different scanning speeds and hatch spacing combinations. The rough surface defect emerged when further increasing the laser power (P &amp;gt; 200 W), leading to a further narrowed printable space.