candidate for schizophrenia, in 2003. In 2002, SK Telecom successfully launched the world's first commercial CDMA 1X EV-DO technology, allowing it to offer 3G telecommunications service. In 2004, SK Telecom enabled satellite DMB service by deploying the world's first DMB satellite. Moreover, in 2006, SK began revitalizing the 3.5-generation mobile phone market and in the following year, completed the construction of the national HSDPA network. In May 2006, SK Telecom started the world's first commercial 3.5-generation HSDPA service, featuring high-quality video telephony and data transmission, and global roaming access. In 2005, SK Networks opened China's first two wholly foreign-owned, gas stations in Shenyang. Then, after exploring Brazilian mining area BM-C-8, SK Corporation developed an oil field where it confirmed the existence of more than 50 million barrels of oil deposits. SK Gas began developing resources overseas when it participated in two mining areas to the west of Russia's Kamchatka peninsula in March 2006. In early 2006, SK Networks also developed Ecol-Green, a biodegradable plastic material. Incheon Oil officially started operations using the SK name in March 2006. SK Energy is currently engaged in 27 oil fields in 15 countries worldwide SKC imported propylene oxide (PO, a chemical used in manufacturing polyurethane) production technology from Germany in May 2006. It is scheduled to produce 100,000 tons of PO from 2008. At the end of 2005, SK Corp. developed a lithium ion battery separator (LiBS) for the first time in Korea, and started selling the product in 2006. In July 2007, SK Group adopted a holding company structure. Under the re-organization, SK's main entity, SK Corporation, was split into an investment company, now SK Inc. and an operating company, now SK Energy. The subsidiary companies that now operate under the central SK Inc. umbrella include: SK Energy, SK Telecom, SK Networks, SKC, SK E&S, SK Shipping and K Power. Recent years In February 2017, SK acquired the polyethylene acrylic acid business of Dow Chemical Company for $370 million, and planned to increase battery production capacity from 1.9 to 3.9 GWh per year at the end of 2018, supplying Kia and Mercedes. In July 2022, SK Group announced a $22 billion investment in the United States semiconductor, green energy bioscience and other technology industries. In total, SK Group will invest over $30 billion in the United States by 2025. Subsidiaries Holdings SK Inc. () is a holding company which resulted when SK Corporation