Laser Alignment Research Articles

LAVOLUTION: Tunable structured light for bridge displacement measurement

Assessing bridge conditions is critical, but field measurements often face challenges like sensor installation and accuracy requirements. This paper introduces a novel approach using structured light (SL) for non-target-based measurements, eliminating the need for physical markers. A tunable SL system, featuring four laser pointers aligned with a commercial camera, was developed to estimate the relative angle between the camera and the target structure, and to accurately calculate the scale factor. The proposed method involves three main processes: (1) laser alignment, (2) angle estimation, and (3) real-time displacement measurement. By precisely aligning the SL system and minimizing discrepancies between projected SL points and an ideal numerical model, the method achieves accurate results. Validation through numerical simulations, lab-scale tests, and full-scale bridge tests demonstrated a maximum error of 2.69% in scale and 2.53% in displacement, confirming the method’s effectiveness and applicability.

Design of a Thomson scattering diagnostic for the SMall Aspect Ratio Tokamak (SMART).

We describe the design of a Thomson scattering (TS) diagnostic to be used on the SMall Aspect Ratio Tokamak (SMART). SMART is a spherical tokamak being commissioned in Spain that aims to explore positive triangularity and negative triangularity plasma scenarios at a low aspect ratio. The SMART TS diagnostic is designed to operate at high spatial resolution, 6mm scattering length in the low-field side and 9mm in the high-field side regions, and a wide dynamic range, electron temperature from 1eV to 1keV and density from 5×1018m-3 to 1×1020m-3, to resolve large gradients formed at the plasma edge and in the scrape-off layer (SOL) under different triangularities and low aspect ratios. A 2J @1064 nm laser will be used that is capable of operating in the burst mode at 1, 2, and 4kHz to investigate fast phenomena and at 30Hz to study 1s (or more) long discharges. The scattered light will be collected over an angular range of 60° - 120° from 28 spatial points in the midplane covering the entire plasma width and the outer midplane SOL. Each scattering signal will be spectrally resolved on five wavelength channels of a polychromator to obtain the electron temperature measurement. We will also present a method to monitor in situ laser alignment in the core during calibrations and plasma operations.

P-089 Sperm motility and sperm DNA fragmentation evaluation after irradiation with a 633nm He-Ne laser in donor samples. An in vitro pilot study

Abstract Study question Does a 633nm laser irradiation on sperm samples improve sperm motility safely? Summary answer 633 nm wavelength He-Ne laser irradiation for 5 and 10 minutes increases slow progressive and non-progressive sperm motility without modification of the DNA fragmentation. What is known already Sperm motility has been hypothesized to increase after light radiation excitation of cytochrome c- oxidase, which boost adenosin triphosphate (ATP) synthesis, in a range of wavelength between 600-1000 nm. One of the main problems of this stimulation is the generation of Reactive Oxigen Species (ROS) that may affect sperm DNA integrity. Previous studies have approached to this field showing different results. Study design, size, duration In vitro pilot study of 15 sperm samples donated for research between June 2022 and October 2023 which were irradiated with a 633nm wavelength He-Ne laser. Each sample was split in 4 aliquots of 10 microliters. To study sperm motility analysis, two videos of each were recorded, before and after irradiation, anonymized and evaluated later by a single embryologist. Sperm motility was annotated according to WHO 2021 criteria. Participants/materials, setting, methods After laser calibration and alignment, sperm samples were irradiated at 37 ºC in a Makler chamber with a continuous emission laser with a gaussian-like beam thirty cm. away for 5,10,15 and 20 minutes. Two videos were obtained for each aliquot, before and after irradiation. Radiant exposure was calculated using the equation y = 1030 x-1,626. Sperm Chromatine Dispersion (SCD) test was employed in 50 µl aliquots to study DNA fragmentation. Shapiro-Wilk and paired t-student tests were employed. Main results and the role of chance We observed a significant increase in slowly progressive motility; -0.075 [-0.12 – 0.024] (p = 0.007); and non-progressive motility; -0.023 [-0.041 – -0.006] (p = 0.011); after irradiating samples between 5 and 10 minutes with a total radiant exposure, 0.4830 and 0.9661 (mW/mm2 * min). Also, for total progressive motility; -0.075 [-0.13 – -0.01] (p = 0.024), and total motility; -0.069 [-0.126 – -0.012) (p = 0.021). No differences were found in sperm DNA fragmentation index after irradiating for 10 minutes; -1.347 [-4.073 - 1.380] (p = 0.32) nor for 20 minutes of irradiation -1.587 [-4.400 - 1.227] (p = 0.25). According to our results, irradiation of sperm samples between 5 and 10 minutes with a 633nm wavelength laser, increases type b and type c motility spermatozoa without affecting sperm DNA fragmentation. Longer irradiations, 15 and 20 minutes, do not show an improvement in sperm motility, neither in sperm DNA fragmentation in our set of data. Limitations, reasons for caution This in vitro pilot study has not been proved in samples to clinical use and our findings need a confirmation with clinical samples in animals to ensure the safety in the conceptions and offspring. We included samples with normal sperm values. Results should be confirmed in samples with motility defects. Wider implications of the findings Our findings are the first step in a new way to modify the sperm motility in vitro throughout laser exposition, which may benefit patients with severe asthenozoospermia without the use of chemical motility inductors. We hope to confirm the safe clinical use in animals before translation to humans. Trial registration number 1909-VGO-082-JA

Hybrid laser-ECM processing of advanced materials in neutral electrolyte without aggressive reagents: Machining performance, removal characteristics and sustainability aspects

The growing need for more energy efficient systems has led to advent of hard and corrosion resistant materials which are difficult to machine with both conventional and non-conventional machining techniques. Although ECM offers athermal and force-free dissolution, the workpiece surface integrity in multicomponent materials is limited with ECM due to several multi-physical phenomena occurring on the surface like selective phase dissolution, passivation, pitting, particle breakout, etc. To tackle these challenges, aggressive acidic and basic reagents are added to the electrolytes. Although these reagents improve the machining performance, they are not sustainable for the environment and human life as they generate harmful waste which is difficult to dispose and recycle. Furthermore, the handling of these aggressive electrolytes requires specialized coatings, resins, filters, catalysts, etc. to protect the machine tools and equipment from damage.Hybrid laser-ECM (LECM) is a relatively novel drill-mill processing technique to process these advanced materials while using neutral electrolytes, thereby potentially reducing the negative impact of using acidic/basic reagents in electrolytes. Under controlled conditions and proper laser alignment, LECM can simultaneously apply laser and EC process energies in the same machining zone to provide synergistic benefits manifesting in terms of dominance of kinetics and thermodynamics over pure electrodynamics in ECM. This provides multi-fold benefits in improving passivation weakening and homogenize multiphase dissolution. Therefore, this study investigates for the first time the machining performance, removal behaviour, reaction products and power/resource consumption of LECM in neutral electrolyte in comparison to ECM in various neutral and basic electrolytes. The NbC–Ni cermet was used as the workpiece material, which is a cobalt-free alternative to conventional WC-Co. The results revealed that LECM in neutral NaNO3 compared to ECM with NaOH addition not only provided better Sa (2.02 μm, 24% ↓), M.R.R. (153 μg/s, 31% ↑), aspect ratio (0.048, 14% ↑) and similar passivation weakening capability while maintaining a nearly neutral pH (8) of the reaction products, but also reduced electrolyte usage by 23.6% with a 16.4% increase in power consumption. These aspects make LECM a sustainable and cost-effective candidate for processing modern passivating multiphase materials like newer cermets, super alloys, high entropy alloys, etc. with nearly same performance as achieved by using ECM with acidic/basic electrolytes. Further fundamental and applied research is needed in LECM to meet the industrial specifications.

The pointing uncertainty Region's analysis of inter-satellite laser alignment systems under multiple uncertainties

Laser inter-satellite links (LISLs) are crucial for enabling rapid information exchange within low earth orbit (LEO) constellations. Previous research on laser link establishment often relied on the idealized probability density function (PDF) of the pointing uncertainty regions (PURs) when designing scan-and-capture methods, neglecting the impact of various practical uncertainties. To address the above issues, there is an urgent need to analyze the practical uncertainties to enhance the stability and reliability of LISL. This paper first provides a comprehensive introduction to the alignment process in LISL and mathematically formulates typical sources of uncertainty errors. Subsequently, a generalized system model (GSM) for laser link establishment was established at three stages: Orbit, Attitude, and Laser terminal. Finally, we integrate uncertainty models into the GSM and propose a PUR generating method to obtain precise PDFs. The research method proposed in this study can consider the influence of multiple uncertainties and generate the PDF for the PURs. Compared with traditional research, the PDF obtained by fitting the oscillation range considering dynamics is more detailed. By analyzing the PDF generated by typical uncertainty errors, it is observed that the orbit initial uncertainty may be the predominant factor influencing the PUR.

Intelligent Laser Emitting and Mode Locking of Solid‐State Lasers Using Human‐Like Algorithms

AbstractSolid‐state lasers based on mode‐locked technology are widely studied for their strong ability of average or peak power scaling and wide wavelength coverage. However, it usually takes a long time and a lot of effort to manually align an ultrafast solid‐state laser to achieve laser emission and stable mode‐locking. Here, an approach based on intelligent human‐like algorithms is proposed for aligning a solid‐state ultrafast laser system. The intelligent system is based on multi‐algorithm fusion and can fully simulate the process of observation, analysis, decision, and action of an experienced experimenter in the adjustment of the laser alignment and mode‐locking. The intelligent adjustment starts from the state of no laser emission, adopts the neural network, the modified augmented random search (ARS) algorithm, random search, and sliding window strategy, and takes the fluorescence and speckle patterns as indications to realize the laser emission and stable mode‐locking automatically. Several validation experiments are conducted using this intelligent system, and the stable mode‐locked pulses can be achieved within 40 s. This technology provides an efficient solution to the ultrafast solid‐state laser that requires full automatic laser emitting and stable mode‐locking for the first time.

Automatic 4-mirrors system for alignment of high-power laser radiation

This paper presents the automated system for minimizing the deviation of the path of passage and the divergence of a secondary radiation source with parameters similar to ones of the main beam of a high-power Ti:Sa laser using mirrors in kinematic mounts on the motorized stages. As an alignment laser, the diode laser with a fiber output was used with radiation characteristics coinciding with the parameters of the main beam (wavelength, beam diameter). The successive approximation algorithm was used to minimize the beam deflection. The positioning accuracy and beam size matching were analyzed on the near-field camera and were equaled to 28.6 µm along the X-axis and 26.4 µm along the Y-axis. Beam size mismatch was equaled to 0.151 mm. The pointing accuracy was analyzed on the far-field sensor and equaled 15.34 µrad along the X axis and 12.03 µrad along the Y axis. The curvature of the wavefront was 0.06 µm.

Algorithm development for automatic laser alignment assessment on an ACR CT phantom and its evaluation on sixteen CT scanners

Purpose. The aim of this study is to develop software to automatically assess the laser alignment on the ACR CT phantom and evaluate its accuracy on sixteen CT scanners. Methods. Software for an automated method of laser alignment assessment on the ACR CT phantom was developed. Laser alignment assessment was based on the positions of the ball-bearing markers at the edge of the ACR CT phantom. The automatic assessment was performed using several steps, including segmentation to acquire the coordinates of the ball-bearing markers and determination of the distances between lines connecting them with lines through the center of the image. A comparison of the results from the automatic method with those from the manual method was performed. The manual measurements were carried out using MicroDicom Viewer. A Mann–Whitney U test was performed to determine the statistical difference between both methods. The evaluation was performed on images of the ACR CT phantom scanned with 16 CT scanners from 5 different CT manufacturers. Results. The results confirmed that our software successfully segments the ball-bearing markers and determines the laser alignment assessment on the ACR CT phantom. Evaluation of the algorithm with images from the 16 CT scanners revealed that the difference between the results from automatic and manual methods were about 0.2 mm with a p value of around 0.7 (no statistical difference). Misalignment in the y-axis was larger than the misalignment in the x-axisfor the majority of the scanners tested. It was found that the phantom tended to be placed 2 mm higher than the iso-center. Conclusions. Software to automatically assess CT laser alignment with the ACR CT phantom was successfully developed and evaluated. The automatic assessment was comparable to manual assessment. In addition, the automatic method was user independent and fast.

Setup accuracy and margins for surface-guided radiotherapy (SGRT) of head, thorax, abdomen, and pelvic target volumes

The goal of the study was to evaluate the inter- and intrafractional patient setup accuracy of target volumes located in the head, thoracic, abdominal, and pelvic regions when using SGRT, by comparing it with that of laser alignment using patient skin marks, and to calculate the corresponding setup margins. A total of 2303 radiotherapy fractions of 183 patients were analyzed. All patients received daily kilovoltage cone-beam computed tomography scans (kV-CBCT) for online verification. From November 2019 until September 2020, patient setup was performed using laser alignment with patient skin marks, and since October 2020, using SGRT. The setup accuracy was measured by the six degrees of freedom (6DOF) corrections based on the kV-CBCT. The corresponding setup margins were calculated using the van Herk formula. Analysis of variance (ANOVA) was used to evaluate the impact of multiple factors on the setup accuracy. The inter-fractional patient setup accuracy was significantly better using SGRT compared to laser alignment with skin marks. The mean three-dimensional vector of the translational setup deviation of tumors located in the thorax, abdomen, and pelvis using SGRT was 3.6 mm (95% confidence interval (CI) 3.3 mm to 3.9 mm) and 4.5 mm using laser alignment with skin marks (95% CI 3.9 mm to 5.2 mm; p = 0.001). Calculation of setup margins for the combined inter- and intra-fractional setup error revealed similar setup margins using SGRT and kV-CBCT once a week compared to laser alignment with skin marks and kV-CBCT every other day. Furthermore, comparable setup margins were found for open-face thermoplastic masks with AlignRT compared to closed-face thermoplastic masks with laser alignment and mask marks. SGRT opens the possibility to reduce the number of CBCTs while maintaining sufficient setup accuracy. The advantage is a reduction of imaging dose and overall treatment time. Open-face thermoplastic masks may be used instead of closed-face thermoplastic masks to increase the patient's comfort.

Comparison investigation on microstructure and properties of dissimilar welds by laser alignment welding and laser offset welding between Al–Si coated 1.5 GPa and novel 2 GPa press hardened steels

Comparison investigation on microstructure and properties of dissimilar welds by laser alignment welding and laser offset welding between Al–Si coated 1.5 GPa and novel 2 GPa press hardened steels

Quantification of systematic errors in the electron density and temperature measured with Thomson scattering at W7-X

The electron density and temperature profiles measured with Thomson scattering at the stellarator Wendelstein 7-X show features which seem to be unphysical, but so far could not be associated with any source of error considered in the data processing.A detailed Bayesian analysis reveals that errors in the spectral calibration cannot explain the features observed in the profiles.Rather, it seems that small fluctuations in the laser position are sufficient to affect the profile substantially.The impact of these fluctuations depends on the laser position itself, which, in turn, provides a method to find the optimum laser alignment in the future.

0450 Backscattered Ultrasound Imaging of the Tongue Correlates with Severity of Obstructive Sleep Apnea in Adults

Abstract Introduction Determination of intervention to manage obstructive sleep apnea (OSA) is dependent on clinical examination, polysomnography results, and imaging analysis. There remains the need of a non-invasive and cost-effective way to correlate relevant upper airway anatomy with severity of obstructive sleep apnea (OSA ) to direct treatment and optimize outcome. We aimed to determine whether ultrasonography with backscattered imaging (BUI) analysis of the tongue correlates with severity of OSA in adults. Methods A prospective, single-center, observational study of a consecutive series of patients (aged18 years and older) visiting our sleep clinic. All included patients had a polysomnography (PSG) within 3 years from the moment of BUI analysis. Patients were excluded if their BMI had changed more than 10%. We used and standardized the submental ultrasound scan with a laser alignment tool and applied BUI analysis to the tongue. Outcomes were correlated to the patients’ AHI, BUI results were compared to only echo intensity. Results Eighty-nine patients were included between July 2020 and March 2022. Mean age was 38.8±12.7 years, mean BMI was 26.7±5.0 kg/m2, and mean AHI was 17.5±16.8 events/h. Significant differences were found between the subgroups with AHI< 15 and □15 events/h at specific regions of the tongue base using BUI analysis, echo intensity showed no significant differences. BUI values showed a positive correlation with AHI, with Pearson correlation coefficient of 0.42 and 0.37, and Spearman correlation coefficient of 0.43 and 0.43 for the A and B regions of the tongue, respectively. Higher BUI values are associated with more severe AHI, even after correction for covariates (BMI and age). Conclusion Standardized ultrasound scanning of the tongue with backscattered imaging analysis yields strong correlation with severity of OSA. With the intrinsic advantages in the use of ultrasonography in outpatient settings, this analysis is pivotal in reducing the gap between anatomy and physiology in clinical decision-making for treating OSA. Support (if any) None

Sound source signal location and tracking system based on STM32

With the progress of science and technology, sound source localization technology has a wide range of applications in urban traffic, digital hearing AIDS, mechanical systems and other fields, especially in noise monitoring and other aspects. In order to solve problems such as failure risk, this technology can accurately determine the location of the problem. At present, low-end manual technology is used in many fields, which is inefficient and a waste of time. Therefore, this paper designed a sound source signal positioning and tracking system based on STM32. The system takes STM32F407VET6 as the control core, and the speaker as the sound source that can emit self-defined regular sound. After the amplification circuits, it is sent to the microcontroller for processing.After sampling, the distance and offset Angle between the test point and the sound source are calculated by calculating the time deviation of the sound signal collected by the two microphones. Then control the steering gear rotation and laser alignment to realize the positioning and tracking of the sound source, and display the distance and offset information between the test point and the sound source in the terminal. With the development of modern technology, sound source localization can be widely used in daily life, and with the development of machine learning, cloud computing and electronic technology, this technology will have a broader application prospect.

Association of Backscattered Ultrasonographic Imaging of the Tongue With Severity of Obstructive Sleep Apnea in Adults

Determining interventions to manage obstructive sleep apnea (OSA) depends on clinical examination, polysomnography (PSG) results, and imaging analysis. There remains the need of a noninvasive and cost-effective way to correlate relevant upper airway anatomy with severity of OSA to direct treatment and optimize outcome. To determine whether backscattered ultrasonographic imaging (BUI) analysis of the tongue is associated with severity of OSA in adults. In this prospective, single-center, diagnostic study of a consecutive series of patients (aged ≥18 years) at a sleep surgery clinic, the 89 included patients had a PSG within 3 years at the time of ultrasonography and BUI analysis between July 2020 and March 2022. Patients were excluded if body mass index had changed more than 10% since time of PSG. A standardized submental ultrasonographic scan with laser alignment was used with B-mode and BUI analysis applied to the tongue. The B-mode and BUI intensity were associated with the apnea-hypopnea index (AHI), a measure of severity of apnea from normal (no OSA) to severe OSA. Ultrasonography and PSG. The main outcomes were BUI parameters and their association with AHI value. Eighty-nine patients were included between July 2020 and March 2022. A total of 70 (78.7%) male patients were included; and distribution by race and ethnicity was 46 (52%) White participants, 22 (25%) Asian participants, and 2 (2%) African American participants, and 19 (21%) others. Median (IQR) age was 37.0 (29.0-48.3) years; median (IQR) BMI was 25.3 (23.2-29.8); and median (IQR) AHI was 11.1 (5.6-23.1) events per hour. At the middle to posterior tongue region, the 4 OSA severity levels explained a significant portion of the BUI variance (η2 = 0.153-0.236), and a significant difference in BUI values was found between the subgroups with AHI values of less than 15 (no OSA and mild OSA) and greater than or equal to 15 (moderate OSA and severe OSA) events per hour. The echo intensity showed no significant differences. The BUI values showed a positive association with AHI, with a Spearman correlation coefficient of up to 0.43. Higher BUI values remained associated with higher AHI after correction for the covariates of BMI and age. In this prospective diagnostic study, standardized BUI analysis of the tongue was associated with OSA severity. With the practicality of ultrasonography, this analysis is pivotal in connecting anatomy with physiology in treatment planning for patients with OSA.

Evaluation of initial patient setup methods for breast cancer between surface-guided radiation therapy and laser alignment based on skin marking in the Halcyon system

BackgroundThis study was conducted to evaluate the efficiency and accuracy of the daily patient setup for breast cancer patients by applying surface-guided radiation therapy (SGRT) using the Halcyon system instead of conventional laser alignment based on the skin marking method.Methods and materialsWe retrospectively investigated 228 treatment fractions using two different initial patient setup methods. The accuracy of the residual rotational error of the SGRT system was evaluated by using an in-house breast phantom. The residual translational error was analyzed using the couch position difference in the vertical, longitudinal, and lateral directions between the reference computed tomography and daily kilo-voltage cone beam computed tomography acquired from the record and verification system. The residual rotational error (pitch, yaw, and roll) was also calculated using an auto rigid registration between the two images based on Velocity. The total setup time, which combined the initial setup time and imaging time, was analyzed to evaluate the efficiency of the daily patient setup for SGRT.ResultsThe average residual rotational errors using the in-house fabricated breast phantom for pitch, roll, and yaw were 0.14°, 0.13°, and 0.29°, respectively. The average differences in the couch positions for laser alignment based on the skin marking method were 2.7 ± 1.6 mm, 2.0 ± 1.2 mm, and 2.1 ± 1.0 mm for the vertical, longitudinal, and lateral directions, respectively. For SGRT, the average differences in the couch positions were 1.9 ± 1.2 mm, 2.9 ± 2.1 mm, and 1.9 ± 0.7 mm for the vertical, longitudinal, and lateral directions, respectively. The rotational errors for pitch, yaw, and roll without the surface-guided radiation therapy approach were 0.32 ± 0.30°, 0.51 ± 0.24°, and 0.29 ± 0.22°, respectively. For SGRT, the rotational errors were 0.30 ± 0.22°, 0.51 ± 0.26°, and 0.19 ± 0.13°, respectively. The average total setup times considering both the initial setup time and imaging time were 314 s and 331 s, respectively, with and without SGRT.ConclusionWe demonstrated that using SGRT improves the accuracy and efficiency of initial patient setups in breast cancer patients using the Halcyon system, which has limitations in correcting the rotational offset.

Continuous-variable quantum key distribution with on-chip light sources

Integrated quantum key distribution (QKD) systems based on photonic chips have high scalability and stability, and are promising for further construction of global quantum communications networks. On-chip quantum light sources are a critical component of a fully integrated QKD system; especially a continuous-variable QKD (CV-QKD) system based on coherent detection, which has extremely high requirements for the light sources. Here, for what we believe is the first time, we designed and fabricated two on-chip tunable lasers for CV-QKD, and demonstrated a high-performance system based on these sources. Because of the high output power, fine tunability, and narrow linewidth, the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals, center wavelength alignment of nonhomologous lasers, and suppression of untrusted excess noise. The system’s secret key rate can reach 0.75 Mb/s at a 50 km fiber distance, and the secure transmission distance can exceed 100 km. Our results mark a breakthrough toward building a fully integrated CV-QKD, and pave the way for a reliable and efficient terrestrial quantum-secure metropolitan area network.

A stability and spatial-resolution enhanced laser absorption spectroscopy tomographic sensor for complex combustion flame diagnosis

A novel stable laser absorption spectroscopy (LAS) tomographic sensor with enhanced stability and spatial resolution is developed and applied to complex combustion flame diagnosis. The sensor reduces the need for laser collimation and alignment even in extremely harsh environments and improves the stability of the received laser signal. Furthermore, a new miniaturized laser emission module was designed to achieve multi-degree of freedom adjustment. The full optical paths can be sampled by 8 receivers, with such arrangement, the equipment cost can be greatly reduced, at the same time, the spatial resolution is improved. In fact, 100 emitted laser paths are realized in a limited space of 200mm×200 mm with the highest spatial resolution of 1.67mm×1.67 mm. The stability and penetrating spatial resolution of the LAS tomographic sensor were validated by both simulation and field experiments on the afterburner flames. Tests under two representative experiment states, i.e., the main combustion and the afterburner operation states, were conducted. Results show that the error under the main combustion state was about 4.32% and, 5.38% at the afterburner operation state. It has been proven that this proposed sensor can provide better tomographic measurements for combustion diagnosis, as an effective tool for improving performances of afterburners.

Laser-induced valence electron excitation in acetylene

Strong-field induced valence electron excitation is a common process in strong field interaction with atoms and molecules. In the case of polyatomic molecules, the effects of ionization from low-lying molecular orbitals and nuclear dynamics during the interaction can play critical roles for electron excitation. In this work, we investigate the involved molecular orbitals in the electron excitation of singly ionized acetylene in a strong laser field using alignment dependence and laser intensity dependence. Additionally, the involved nuclear dynamics during the electron excitation are identified from the difference in the kinetic energy release and the angular distribution of laser-induced dissociation with different pulse durations and intensities. The laser intensity dependence clearly shows the relative strength change of two excitation pathways in the measured momentum and angle-resolved distributions.

A laser guide technique: a novel method for accurate acetabular cup alignment in total hip arthroplasty

For accurate cup alignment without navigation in total hip arthroplasty (THA), we developed a “laser guide technique.” The major purposes of this paper are to introduce the technique and compare its accuracy with a conventional manual technique. As a clinical outcome, the dislocation rate was reviewed. Our laser guide technique, which includes preoperative postural adjustment and intraoperative angular reference, has been detailed in the manuscript. 599 hips in 523 patients who underwent primary THA with piriformis-sparing posterolateral approach in April 2010–March 2016 were reviewed. Patients were divided into three groups: conventional group (135 hips), laser guide group (80 hips), and laser + radiographic alignment guide group (384 hips). Radiographic inclination (RI) and radiographic anteversion (RA) errors were evaluated. The dislocation rate was reviewed in 540 hips in 476 patients who were followed up > 2 years postoperatively. Absolute values of the RI/RA error in the three groups were 5.3° ± 4.0°/6.5° ± 4.5°, 4.0° ± 2.8°/4.9° ± 4.4°, and 3.3° ± 2.6°/3.6° ± 2.8°, respectively, indicating substantially enhanced accuracy with laser and radiographic alignment guide. The dislocation rates were 2.5% (3/119) and 0.2% (1/421) in the conventional and laser groups, respectively. Our novel laser guide technique considerably enhanced cup alignment accuracy, suggesting its potential applicability for THA in the lateral decubitus position.

Front Cover: In situ single crystal growth of tris (trimethylsilyl)phosphate, (Me 3 SiO) 3 PO (Z. Anorg. Allg. Chem. 18/2022)

The cover picture shows the laser-induced in situ growing of (Me3SiO)3PO crystals on a single crystal diffractometer. The nozzle in the upper part of the figure provides a cold nitrogen stream on the polycrystalline sample in the capillary attached to the goniometer of the diffractometer. The left part of the picture illustrates how the powder diffraction rings transform into distinct diffraction spots of the grown single crystals. The resulting crystal structure is shown in the right part of the figure. The crystallization is achieved using a non-visible high energy IR laser. Thus, for the visualisation of the laser beam, we used the red-colored alignment laser. (DOI: 10.1002/zaac.202200184).