Mechanism of dynamic plasma motion in internal modification of glass by fs-laser pulses at high pulse repetition rate.

Evolution of free-electron density in internal modification of glass by fs-laser pulses at high pulse repetition rates is simulated based on rate equation model, which is coupled with thermal conduction model in order to incorporate the effect of thermal ionization. Model shows that highly absorbing small plasma generated near the geometrical focus moves toward the laser source periodically to cover the region, which is much larger than focus volume. The simulated results agree qualitatively with dynamic motion of plasma produced in internal modification of borosilicate glass by fs-laser pulses at 1 MHz through the observation using high-speed video camera. The paper also reveals the physical mechanism of the internal modification of glass when heat accumulation is significant.

Target geometry and rigidity determines laser-induced cavitation bubble transport and nanoparticle productivity - a high-speed videography study.

Laser-induced cavitation has mostly been studied in bulk liquid or at a two-dimensional wall, although target shapes for the particle synthesis may strongly affect bubble dynamics and interfere with particle productivity. We investigated the dynamics of the cavitation bubble induced by pulsed-laser ablation in liquid for different target geometries with high-speed laser microsecond videography and focus on the collapse behaviour. This method enables us observations in a high time resolution (intervals of 1 µs) and single-pulse experiments. Further, we analyzed the nanoparticle productivity, the sizes of the synthesized nanoparticles and the evolution of the bubble volume for each different target shape and geometry. For the ablation of metal (Ag, Cu, Ni) wire tips a springboard-like behaviour after the first collapse is observed which can be correlated with vertical projectile motion. Its turbulent friction in the liquid causes a very efficient transport and movement of the bubble and ablated material into the bulk liquid and prevents particle redeposition. This effect is influenced by the degree of freedom of the wire as well as the material properties and dimensions, especially the Young's modulus. The most efficient and largest bubble movement away from the wire was observed for a thin (500 µm) silver wire with velocities up to 19.8 m s(-1) and for materials with a small Young's modulus and flexural rigidity. We suggest that these observations may contribute to upscaling strategies and increase of particle yield towards large synthesis of colloids based on targets that may continuously be fed.

[Cases of Three Patients with Gastric Cancer and Metastasis to the Skeletal Muscle].

Metastasis to the skeletal muscle from gastric cancer is relatively rare. We report cases of 3 patients undergoing chemotherapy for gastric cancer with metastasis to the skeletal muscle. Case 1: A man in his 70s was diagnosed with advanced gastric cancer (cT4N3M1P0, stage IV), with metastasis to the lung, brain, lymph node, and iliopsoas muscle. Case 2: A man in his 60s was diagnosed with advanced gastric cancer (cT3N3M1P0, stage IV), with metastasis to the brain, lung, lymph node, and iliopsoas muscle. Case 3: A man in his 50s was diagnosed with advanced gastric cancer (cT4N3M1P0, stage IV), with metastasis to the urinary duct, lymph node, back muscle, and iliopsoas muscle. All 3 patients died within 7-8 months after the diagnosis due to progressive disease despite chemotherapy. The prognosis of these 3 patients was significantly poorer than that of patients in our hospital with metastasis not involving the skeletal muscle (p<0.01). Accordingly, metastasis to the skeletal muscle may be an adverse prognostic factor in gastric cancer.

Effect of liquid-sheet thickness on detection sensitivity for laser-induced breakdown spectroscopy of aqueous solution.

For aqueous-solution-based elemental analysis, we used a thin liquid sheet (µm-scale thickness) in laser-induced breakdown spectroscopy with nanosecond laser pulses. Laser-induced plasma is emitted by focusing a pulsed Nd:YAG laser (1064 nm) on a 5- to 80-µm-thick liquid sheet in air. To optimize the conditions for detecting elements, we studied how the signal-to-background ratio (SBR) for Hα Balmer and Na-neutral emission lines depends on the liquid-sheet thickness. The SBR of the Hα Balmer and Na-neutral lines was maximized for a sheet thickness of ~20 µm at the laser energy of 100 mJ. The hydrodynamics of liquid flow induced by the laser pulse was analyzed by laser flash shadowgraph imaging. Time-resolved observation of the hydrodynamics and plasma emission suggests that the dependence of the SBR on the liquid-sheet thickness is correlated with the volume of flowing liquid that interacts with the laser pulses.

Lower limb kinematic changes during gait after hallux valgus surgery: A prospective observational study.

BACKGROUND: Patients with hallux valgus are known to alter lower limb joint kinematics during gait. However, little information is available about gait changes following hallux valgus surgery. We aimed to longitudinally investigate lower limb kinematic changes at the mid and terminal stances of gait after hallux valgus surgery. METHODS: This prospective observational study included 11 female patients (17 feet), who underwent first metatarsal osteotomy. Gait analyses were performed preoperatively and 1- and 2-year postoperatively using a three-dimensional motion capture system. Toe-out angle, ankle, knee, and hip joint angles during gait were calculated from the recorded data. The spatiotemporal parameters and these angles at the mid and terminal stances of gait were statistically compared between preoperative and postoperative periods. FINDINGS: All spatiotemporal parameters remained unchanged postoperatively. The toe-out angle was significantly greater at 1- and 2-year postoperatively. The ankle pronation angle, the knee abduction angle, and the hip adduction angle at the mid and terminal stances of gait were smaller postoperatively compared to the preoperative. These angular changes showed a similar trend at 1 and 2 years postoperatively. However, the postoperative changes of the sagittal joint angles were relatively small. INTERPRETATION: Hallux valgus surgery can affect the toe-out angle and the lower limb coronal kinematics at the mid and terminal stances of gait in patients with hallux valgus. However, surgical correction of hallux valgus deformity did not directly improve the gait characteristics in patients with hallux valgus.

Isolated Talonavicular Arthrodesis for Traumatic Talonavicular Arthritis: Report of 2 Cases With Gait Analyses.

Isolated talonavicular arthrodesis is one of the surgical procedures for patients with talonavicular arthritis. However, the 3-dimensional kinematic behavior of the hip, knee, and foot/ankle complex during walking after the arthrodesis remains unclear. The clinical outcomes and gait analyses of 2 cases who underwent isolated arthrodesis for talonavicular osteoarthritis with chronic dislocated navicular fracture are presented. Gait analysis was carried out in both cases 1 year after surgery to clarify the side-to-side differences in the ranges of motion of the hip, knee, and foot/ankle complex during walking. Both cases showed good clinical results and radiographic bone union. The kinematic data of the gait analyses showed considerable restriction in the range of motion of the ankle in all 3-dimensional planes for the fused foot compared with the contralateral side. Additionally, hyperextension of the knee in the late stance of gait on the operated side was observed in both cases. When talonavicular arthrodesis was performed for talonavicular osteoarthritis with chronic dislocated navicular fracture, postoperative generalized stiffness of the ankle and future disorder of the knee should be considered.Levels of Evidence: Level V: Case report.