Yoon-sik Kim

Superconductivity below 20 K in heavily electron-doped surface layer of FeSe bulk crystal

A superconducting transition temperature (Tc) as high as 100 K was recently discovered in one monolayer FeSe grown on SrTiO3. The discovery ignited efforts to identify the mechanism for the markedly enhanced Tc from its bulk value of 8 K. There are two main views about the origin of the Tc enhancement: interfacial effects and/or excess electrons with strong electron correlation. Here, we report the observation of superconductivity below 20 K in surface electron-doped bulk FeSe. The doped surface layer possesses all the key spectroscopic aspects of the monolayer FeSe on SrTiO3. Without interfacial effects, the surface layer state has a moderate Tc of 20 K with a smaller gap opening of 4.2 meV. Our results show that excess electrons with strong correlation cannot induce the maximum Tc, which in turn reveals the need for interfacial effects to achieve the highest Tc in one monolayer FeSe on SrTiO3.

A traditional Korean multiple herbal formulae (Yuk-Mi-Jihwang-Tang) attenuates acute restraint stress-induced brain tissue oxidation

Abstract We aimed to evaluate the protective effects of Yuk-Mi-Jihwang-Tang (YJT) against acute restraint stress-induced brain oxidative damage. A water extract of YJT was prepared and subjected to high performance liquid chromatography – diode array detector-mass spectrometry (HPLC-DAD-MS). Thirty-six heads of C57BL/6J male mice (7 weeks) were divided into six groups (n = 6/group). The mice were orally administrated YJT (0, 50, 100, or 200 mg/kg) or vitamin C (100 mg/kg) for 5 consecutive days before 6 h of acute restraint stress. In the brain tissue, lipidperoxidation, antioxidant components, and pro-inflammatory cytokines were measured, and the serum corticosterone level was determined. Acute restraint stress-induced notably increased lipid peroxidation in brain tissues, and pretreatment with YJT showed a significant decreased the lipid peroxidation levels (p< 0.05). The levels of antioxidant components including total glutathione contents, activities of SOD and catalase were remarkably depleted by acute restraint stress, whereas these alterations were significantly restored by treatment with YJT (p< 0.05 or p< 0.01). The restraint stress markedly increased pro-inflammatory cytokines, such as TNF-α and IL-6 in the gene expression and protein levels (p< 0.05 or p< 0.01). Pretreatment with YJT significantly attenuated serum corticosterone (200 mg/kg, p < 0.05). YJT drastically attenuated the levels of 4- HNE, HO-1, Nox 2 and iNOSwhich were elevated during acute restraint stress, whereas the Nrf2 level was increased in brain tissue protein levels. Our data suggest that YJT protects the brain tissue against oxidative damage and regulates stress hormones.

ACE Reduces Metabolic Abnormalities in a High-Fat Diet Mouse Model

The medicinal plants Artemisia iwayomogi (A. iwayomogi) and Curcuma longa (C. longa) radix have been used to treat metabolic abnormalities in traditional Korean medicine and traditional Chinese medicine (TKM and TCM). In this study we evaluated the effect of the water extract of a mixture of A. iwayomogi and C. longa (ACE) on high-fat diet-induced metabolic syndrome in a mouse model. Four groups of C57BL/6N male mice (except for the naive group) were fed a high-fat diet freely for 10 weeks. Among these, three groups (except the control group) were administered a high-fat diet supplemented with ACE (100 or 200 mg/kg) or curcumin (50 mg/kg). Body weight, accumulation of adipose tissues in abdomen and size of adipocytes, serum lipid profiles, hepatic steatosis, and oxidative stress markers were analyzed. ACE significantly reduced the body and peritoneal adipose tissue weights, serum lipid profiles (total cholesterol and triglycerides), glucose levels, hepatic lipid accumulation, and oxidative stress markers. ACE normalized lipid synthesis-associated gene expressions (peroxisome proliferator-activated receptor gamma, PPARγ; fatty acid synthase, FAS; sterol regulatory element-binding transcription factor-1c, SREBP-1c; and peroxisome proliferator-activated receptor alpha, PPARα). The results from this study suggest that ACE has the pharmaceutical potential reducing the metabolic abnormalities in an animal model.