An estimate has been made of the feasibility of a metallurgical puri®cation process, the NEDO (New Energy and Industrial Technology Development Organization) melt-puri®cation process, for manufacturing solar-grade silicon from metallurgical-grade silicon. Equipment has been developed to pilot manufacturing plant scale. The system comprises an electron-beam furnace for phosphorus removal and a plasma furnace for boron removal. Each furnace has a mold for directional solidi®cation to remove metallic impurities. The concentration of each impurity in the silicon ingot puri®ed through the whole process satis®ed the solar-grade level. The Solar-grade silicon produced showed p-type polarity and resistivity within the range 0Á5±1Á5 cm.

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Various complications after microendoscopic discectomy (MED) are well known, but postoperative discal cyst is a unique and relatively unknown complication. Here, we report on two teenage patients who presented with postoperative discal cyst after MED for herniated nucleus pulposus (HNP), which resolved after conservative treatment. The patients were diagnosed with HNP at L4-5 and L5-S1 based on MRI and then treated by MED. Postoperative discal cyst was diagnosed on MRI after recurrence of symptoms. Both patients were managed conservatively. T2-weighted MRI demonstrated hyperintense collections adjacent to the operated intervertebral disc level, which were communicating with the corresponding disc annulus. Because the clinical symptoms were relatively mild, the patients were managed conservatively; both made a complete clinical recovery with radiological evidence of improvement. Postoperative discal cyst is a relatively unknown complication after MED for HNP. Surgeons should be aware of this postoperative complication when operating on young individuals with HNP.