Korea University

About: Korea University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Catalysis. The organization has 39756 authors who have published 82424 publications receiving 1860927 citations. The organization is also known as: Bosung College & Bosung Professional College.

CNS-derived glia ensheath peripheral nerves and mediate motor root development

Abstract: Motor function requires that motor axons extend from the spinal cord at regular intervals and that they are myelinated by Schwann cells. Little attention has been given to another cellular structure, the perineurium, which ensheaths the motor nerve, forming a flexible, protective barrier. Consequently, the origin of perineurial cells and their roles in motor nerve formation are poorly understood. Using time-lapse imaging in zebrafish, we show that perineurial cells are born in the CNS, arising as ventral spinal-cord glia before migrating into the periphery. In embryos lacking perineurial glia, motor neurons inappropriately migrated outside of the spinal cord and had aberrant axonal projections, indicating that perineurial glia carry out barrier and guidance functions at motor axon exit points. Additionally, reciprocal signaling between perineurial glia and Schwann cells was necessary for motor nerve ensheathment by both cell types. These insights reveal a new class of CNS-born glia that critically contributes to motor nerve development.

When fast growing economies slow down: international evidence and implications for china

Abstract: Using international data starting in 1957, we construct a sample of cases where fast-growing economies slow down. The evidence suggests that rapidly growing economies slow down significantly, in the sense that the growth rate downshifts by at least 2 percentage points, when their per capita incomes reach around $17,000 US in year-2005 constant international prices, a level that China should achieve by or soon after 2015. Among our more provocative findings is that growth slowdowns are more likely in countries that maintain undervalued real exchange rates.

Trade barriers and trade flows across countries and industries

Abstract: We use disaggregated data on trade flows, production, and trade barriers for 41 countries in 1988 to examine the political and economic determinants of non-tariff barriers, as well as the impact of protection (both tariff and non-tariff) on trade flows. We use an econometric framework that allows for the simultaneous detennination of trade barriers and trade flows. Our results are consistent with political-economy theories of the determinants of protection: even after accounting for industry-specific factors, nations tend to protect industries that are weak, in decline, and threatened by import competition. Countries also give more protection to large industries; these might be thought of as politically important. Nations use tariffs, non-tariff barriers, and exchange rate controls as complementary instruments of protection.

Charge pump with perfect current matching characteristics in phase-locked loops

Abstract: Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset, which increases spurs in the PLL output signals. In particular, it reduces the locking range in wide range PLLs with a dual loop scheme. A new charge pump circuit with perfect current matching characteristics is proposed. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. It shows nearly perfect current matching characteristics over the whole VCO input range, and the amount of the reference spur is <-75 dBc in the PLL output signal. The charge pump circuit is implemented in a 0.25 /spl mu/m CMOS process.