Percutaneous Endoscopic Transforaminal Decompression in the Treatment of Patients with Migrated Lumbar Disc Herniation: A Retrospective Study.

OBJECTIVE: We aimed to discuss the surgical strategies, safety and clinical efficacy of percutaneous endoscopic transforaminal decompression for the treatment of patients with migrated lumbar disc herniation. METHODS: This is a retrospective study. From May 2014 to April 2017, a total of 56 patients (32 men and 24 women) with migrated lumbar disc herniation were operated on by percutaneous endoscopic decompression via transforaminal approach. All enrolled patients had clinical symptoms with radiculopathy, and were identified as single-level, soft herniated disc by computed tomography and magnetic resonance imaging. Clinical efficacy were evaluated chiefly by leg pain visual analogue scale score, Oswestry disability index score, and modified MacNab criteria. RESULTS: Patients were all successfully treated by percutaneous endoscopic transforaminal decompression, with an mean operation time of 63 ± 12 minutes. The patients were followed up for a mean duration of 15 ± 2.7 months (range 12-18 months). The leg pain visual analogue scale score was dropped from 8.2 ± 1.9 preoperatively to 2.4 ± 1.5, 2.2 ± 1.3, and 1.8 ± 1.1 at 1, 6, and 12 months after the operation, respectively. Similarly, the Oswestry disability index score was also decreased from 62.4 ± 8.2 preoperatively to 18.4 ± 6.2, 12.6 ± 5.1, and 9.2 ± 3.4 at 1, 6, and 12 months postoperatively. There were 38 excellent cases, 13 good cases, and 5 fair cases by the assessment method of modified MacNab criteria at 12 months after the operation, with an excellent and good rate of 91.07%. Two cases were complicated with low extremity numbness, which were recovered by conservative treatment in 3 weeks. No persistent neurological deficit or infection occurred in this group postoperatively. CONCLUSIONS: We consider that percutaneous endoscopic decompression via transforaminal approach provided a safe, effective and minimally invasive alternative for the treatment of patients with migrated lumbar disc herniation.

First-principles calculations of mechanical and thermodynamic properties of tetragonal Be12Ti.

The elastic and thermodynamic properties of tetragonal Be12Ti under high temperature and pressure are investigated by first-principles calculations based on pseudopotential plane-wave density functional theory (DFT) within the generalized gradient approximation (GGA) and quasi-harmonic approximation (QHA). The calculated lattice parameters and bulk modulus are in good agreement with the available experimental data. The calculated elastic constants of Be12Ti increase monotonously with increasing pressure, and the elastic stability criterion and the phonon dispersion calculation show that the Be12Ti crystal satisfies the mechanical and dynamic stability under applied pressure (0-100 GPa). The related mechanical properties such as bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) are also studied for polycrystalline of Be12Ti; the calculated B/G value shows that Be12Ti behaves in a brittle manner, and higher pressure can significantly improve the brittleness of Be12Ti. The elastic anisotropy is demonstrated by the elastic anisotropy factors. The direction-dependent Young's modulus and bulk modulus of Be12Ti are dealt with in detail under pressure from 0 GPa to 100 GPa. The pressure and temperature dependencies of the relative volume, the bulk modulus, the elastic constants, the heat capacity and the thermal expansion coefficient, as well as the entropy are obtained and discussed using the quasi-harmonic approximation in the ranges of temperature 0-1600 K and pressure 0-100 GPa.

Investigation of Surface Morphology of 6H-SiC Irradiated with He⁺ and H2⁺ Ions.

Light ion implantation is one of the important procedures of smart cut for SiC-based semiconductor fabrication. This work investigated the surface morphologies and microstructures of single crystal 6H-SiC irradiated by one or both of H2⁺ and He⁺ ions at room temperature and then annealed at specific temperatures. Blisters evolved from the coalescence of H nanocracks were formed in the H2⁺ and He⁺+H2⁺ irradiated sample surface, while circular ripples originated from the pressure release of helium bubbles after high temperature annealing were formed in the He⁺ irradiated sample surface. The lateral radius a of the blisters in the irradiated sample with low H2⁺ fluence was larger than that in the irradiated sample with high H2⁺ fluence and with He⁺+H2⁺ ions. About 8-58% of implanted H atoms contributed to the formation of the blisters. Compared with other irradiated samples, the ratio of w0/a and the density of the blisters in the He⁺+H2⁺ irradiated samples were largest. The stress field of the blisters was simulated using finite element method and the inner pressure in the blisters was also calculated. The corresponding mechanism was analyzed and discussed.

Recrystallization-Induced Surface Cracks of Carbon Ions Irradiated 6H-SiC after Annealing.

Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ion irradiation induced SiC amorphization, but the surface was smooth and did not have special structures. During the annealing process, the amorphous SiC was recrystallized to form columnar crystals that had a large amount of twin structures. The longer the annealing time was, the greater the amount of recrystallized SiC would be. The recrystallization volume fraction was accorded with the law of the Johnson-Mehl-Avrami equation. The surface morphology consisted of tiny pieces with an average width of approximately 30 nm in the annealed SiC. The volume shrinkage of irradiated SiC layer and the anisotropy of newly born crystals during annealing process produced internal stress and then induced not only a large number of dislocation walls in the non-irradiated layer but also the initiation and propagation of the cracks. The direction of dislocation walls was perpendicular to the growth direction of the columnar crystal. The longer the annealing time was, the larger the length and width of the formed crack would be. A quantitative model of the crack growth was provided to calculate the length and width of the cracks at a given annealing time.

Evolution of Helium Bubbles and Discs in Irradiated 6H-SiC during Post-Implantation Annealing.

The single crystal 6H-SiC with [0001] crystal direction irradiated by 400 keV He⁺ ions with 1 × 1017 ions/cm² fluence at 400 °C were annealed at 600, 900, 1200 and 1400 °C for different durations. The evolution of helium bubbles and discs was investigated by transmission electron microscopy. An irradiated layer distributed with fine helium bubbles was formed with a width of ~170 nm after helium ion irradiation. The size of gas bubbles increased with increasing annealing time and temperature and finally reached stable values at a given annealing temperature. According to the relationship between the bubble radii and annealing time, an empirical formula for calculating the bubble radii at the annealing temperature ranged from 600 to 1400 °C was given by fitting the experiment data. Planar bubble clusters (discs) were found to form on (0001) crystal plane at both sides of the bubble layer when the annealing temperature was at the range of 800-1200 °C. The mechanism of bubble growth during post-implantation annealing and the formation of bubble discs were also analyzed and discussed.

Energy-Efficient Control with Harvesting Predictions for Solar-Powered Wireless Sensor Networks.

Wireless sensor networks equipped with rechargeable batteries are useful for outdoor environmental monitoring. However, the severe energy constraints of the sensor nodes present major challenges for long-term applications. To achieve sustainability, solar cells can be used to acquire energy from the environment. Unfortunately, the energy supplied by the harvesting system is generally intermittent and considerably influenced by the weather. To improve the energy efficiency and extend the lifetime of the networks, we propose algorithms for harvested energy prediction using environmental shadow detection. Thus, the sensor nodes can adjust their scheduling plans accordingly to best suit their energy production and residual battery levels. Furthermore, we introduce clustering and routing selection methods to optimize the data transmission, and a Bayesian network is used for warning notifications of bottlenecks along the path. The entire system is implemented on a real-time Texas Instruments CC2530 embedded platform, and the experimental results indicate that these mechanisms sustain the networks' activities in an uninterrupted and efficient manner.