Sedentism, Settlements, and Radiocarbon Dates of Neolithic Korea

There are two conflicting models regarding the role of the Neolithic millet cultivation in the appearance of the Bronze Age farming economy in South Korea. The “continuity model” suggests that the emergence of a farming economy was a consequence of increasing sedentism, and that millet cultivation practiced during the Neolithic played a significant role in the transition to the Bronze Age. On the contrary, the “discontinuity model” suggests that the appearance of the Bronze Age farming economy heavily dependent on rice had little to do with previous millet cultivation in the Neolithic and the degree of sedentism during the latest Neolithic was very low. We test these models by looking into a temporal variation of sedentism, by quantitatively analyzing the quantity of pit houses and settlements based on relative chronology and radiocarbon dates. Sedentary settlements with small-scale millet cultivation appeared in the central-western Korea during the early fourth millennium b.c. They increased sharply during the late fourth millennium b.c. and also appeared in central-eastern and southern Korea, but they almost disappeared in central and southern Korea from the late third millennium b.c., suggesting a return to increased mobility and/or sharp decrease in population. Hence a continuity model for the emergence of a farming economy cannot be accepted. We suggest environmental deterioration as a prime mover for both the appearance of millet cultivation during the fourth millennium b.c. and the disappearance of sedentary settlement from the late third millennium b.c. in Korea

Nano-structure fabrication of GaAs using AFM tip-induced local oxidation method: different doping types and plane orientations

In this study, we have fabricated nano-scaled oxide structures on GaAs substrates that are doped in different conductivity types of p- and n-types and plane orientations of GaAs(100) and GaAs(711), respectively, using an atomic force microscopy (AFM) tip-induced local oxidation method. The AFM-induced GaAs oxide patterns were obtained by varying applied bias from approximately 5 V to approximately 15 V and the tip loading forces from 60 to 180 nN. During the local oxidation, the humidity and the tip scan speed are fixed to approximately 45% and approximately 6.3 μm/s, respectively. The local oxidation rate is further improved in p-type GaAs compared to n-type GaAs substrates whereas the rate is enhanced in GaAs(100) compared to and GaAs(711), respectively, under the identical conditions. In addition, the oxide formation mechanisms in different doping types and plane orientations were investigated and compared with two-dimensional simulation results

Economic shocks, current account and macroeconomic adjustment : theory and practice in Korea

The main purpose of this thesis is to identify the dynamic effects of exogenous economic shocks on the macroeconomic adjustment in a small open resource-poor economy, Korea. It is well known that the macroeconomic adjustment process of an open economy is best analyzed within an intertemporal general equilibrium framework. However, empirical application of the framework has been very limited despite its theoretical elaborateness. This thesis provides one of the possible solutions to the apparent problem discussed above. To analyze the effects of exogenous economic shocks on macroeconomic adjustment, an intertemporal general equilibrium model is developed, and the effects of an imported intermediate input price shock as well as various government policy shocks are analyzed. By introducing a risk premium to the real interest rate and imported intermediate input in production process, quite realistic theoretical predictions are obtained about macroeconomic adjustment process. The basic framework is, then, extended to be applied empirically. At this stage, the role of government is explicitly introduced as a Stackelberg leader against the producer and the consumer. The information structure among the players are assumed to be open-loop. The resulting behavioral decision functions for the three players are econometrically estimated with the assumption of rational expectations. The estimation results of the forward-looking behavioral equations are quite satisfactory. Additionally, simulation analysis is carried out to identify the quantitative effects of each individual exogenous economic shock. The simulation results are, by and large, consistent with the qualitative results. The main advantage of the simulation analysis was its ability to decompose separate macroeconomic effects according to their causes and origins. The analysis provides a clear picture of how the macroeconomy operates in response to exogenous economic shocks. Among exogenous shocks, the price of imported intermediate input, the world real interest rate and the real wage are shown to have a crucial importance in macroeconomic adjustment process in Korea

Metal work-function-dependent barrier height of Ni contacts with metal-embedded nanoparticles to 4H-SiC

Metal, typically gold [Au], nanoparticles [NPs] embedded in a capping metal contact layer onto silicon carbide [SiC] are considered to have practical applications in changing the barrier height of the original contacts. Here, we demonstrate the use of silver [Ag] NPs to effectively lower the barrier height of the electrical contacts to 4H-SiC. It has been shown that the barrier height of the fabricated SiC diode structures (Ni with embedded Ag-NPs) has significantly reduced by 0.11 eV and 0.18 eV with respect to the samples with Au-NPs and the reference samples, respectively. The experimental results have also been compared with both an analytic model based on Tung's theory and physics-based two-dimensional numerical simulations

Monte Carlo Simulation of Lyman Alpha Scattering and Application to Damped Lyman Alpha Systems

A Monte Carlo code to solve the transfer of Lyman alpha (Lya) photons is developed, which can predict the Lya image and two-dimensional Lya spectra of a hydrogen cloud with any given geometry, Lya emissivity, neutral hydrogen density distribution, and bulk velocity field. We apply the code to several simple cases of a uniform cloud to show how the Lya image and emitted line spectrum are affected by the column density, internal velocity gradients, and emissivity distribution. We then apply the code to two models for damped Lya absorption systems: a spherical, static, isothermal cloud, and a flattened, axially symmetric, rotating cloud. If the emission is due to fluorescence of the external background radiation, the Lya image should have a core corresponding to the region where hydrogen is self-shielded. The emission line profile has the characteristic double peak with a deep central trough. We show how rotation of the cloud causes the two peaks to shift in wavelength as the slit is perpendicular to the rotation axis, and how the relative amplitude of the two peaks is changed. In reality, damped Lya systems are likely to have a clumpy gas distribution with turbulent velocity fields, which should smooth the line emission profile, but should still leave the rotation signature of the wavelength shift across the system.Comment: 19 pages, 17 eps figures. One panel is added in Fig.1 to show the recoil effect. Revisions are made in response to the referee's comments. Accepted for publication in Ap

Sericea lespedeza (Lespedeza cuneata) whole plant extract enhances rat muscle mass and sperm production by increasing the activity of NO-cGMP pathway and serum testosterone

Purpose: To analyze the effects of an aqueous extract of Sericea lespedeza (SL) on rat male menopause.Methods: Levels of nitric oxide (NO), endothelial nitric oxide synthase (NOS), cGMP, and prostaglandin E2 (PGE2) in the penile corpus cavernosum of the rats were evaluated using appropriate kits. Serum levels of dihydrotestosterone (DHT), testosterone, sex hormone-binding globulin (SHBG), and 17-beta hydroxysteroid dehydrogenases (17β-HSD) were measured with enzyme-linked immunosorbent assay kits. Total and motile sperms were counted on a hemocytometer. Histological changes in rat testis and epididymis were analyzed with hematoxylin and eosin staining.Results: The levels of NO, NOS, and cGMP (but not PGE2) increased in a dose-dependent manner (p< 0.05) upon administration of an aqueous extract of SL (AESL), while levels of DHT, 17β-HSD, and testosterone increased in the group administered with 300 mg/kg of AESL. Epididymal sperm count increased by 24 % in such rats compared to controls (p < 0.05).Conclusion: The aqueous extract of SL improves sperm count and muscle mass in rats by increasing the levels of NO, NOS, cGMP and testosterone. Thus, SL extract can potentially be developed as an alternative therapeutic agent for clinical management of TDS. Keywords: NO-cGMP, Testosterone, Hormones, Sperm count, Muscle mass, Sericea lespedeza, Lespedeza cuneat

FK228 Analogues Induce Fetal Hemoglobin in Human Erythroid Progenitors

Fetal hemoglobin (HbF) improves the clinical severity of sickle cell disease (SCD), therefore, research to identify HbF-inducing agents for treatment purposes is desirable. The focus of our study is to investigate the ability of FK228 analogues to induce HbF using a novel KU812 dual-luciferase reporter system. Molecular modeling studies showed that the structure of twenty FK228 analogues with isosteric substitutions did not disturb the global structure of the molecule. Using the dual-luciferase system, a subgroup of FK228 analogues was shown to be inducers of HbF at nanomolar concentrations. To determine the physiological relevance of these compounds, studies in primary erythroid progenitors confirmed that JMA26 and JMA33 activated HbF synthesis at levels comparable to FK228 with low cellular toxicity. These data support our lead compounds as potential therapeutic agents for further development in the treatment of SCD