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 & Thin film. The organization has 39756 authors who have published 82424 publications receiving 1860927 citations. The organization is also known as: Bosung College & Bosung Professional College.

Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets.

Abstract: Fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnetic Gd23Fe67.4Co9.6 thin films at the angular momentum compensation point. In particular, at this point, the field-driven domain wall mobility is found to be enhanced. Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices1,2. A central motivation towards this direction is that antiferromagnetic spin dynamics is expected to be much faster than its ferromagnetic counterpart3. Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs4,5,6. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored, mainly because of the magnetic field immunity of antiferromagnets7. Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare earth–3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility is remarkably enhanced up to 20 km s−1 T−1. The collective coordinate approach generalized for ferrimagnets8 and atomistic spin model simulations6,9 show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.

The Role of NiO Doping in Reducing the Impact of Humidity on the Performance of SnO2-Based Gas Sensors: Synthesis Strategies, and Phenomenological and Spectroscopic Studies

Abstract: The humidity dependence of the gas-sensing characteristics in SnO2-based sensors, one of the greatest obstacles in gas-sensor applications, is reduced to a negligible level by NiO doping. In a dry atmosphere, undoped hierarchical SnO2 nanostructures prepared by the self-assembly of crystalline nanosheets show a high CO response and a rapid response speed. However, the gas response, response/recovery speeds, and resistance in air are deteriorated or changed significantly in a humid atmosphere. When hierarchical SnO2 nanostructures are doped with 0.64–1.27 wt% NiO, all of the gas-sensing characteristics remain similar, even after changing the atmosphere from a dry to wet one. According to diffuse-reflectance Fourier transform IR measurements, it is found that the most of the water-driven species are predominantly absorbed not by the SnO2 but by the NiO, and thus the electrochemical interaction between the humidity and the SnO2 sensor surface is totally blocked. NiO-doped hierarchical SnO2 sensors exhibit an exceptionally fast response speed (1.6 s), a fast recovery speed (2.8 s) and a superior gas response (Ra/Rg = 2.8 at 50 ppm CO (Ra: resistance in air, Rg: resistance in gas)) even in a 25% r.h. atmosphere. The doping of hierarchical SnO2 nanostructures with NiO is a very-promising approach to reduce the dependence of the gas-sensing characteristics on humidity without sacrificing the high gas response, the ultrafast response and the ultrafast recovery.

Sarcopenia: Definition, Epidemiology, and Pathophysiology

Abstract: The epidemiological trends that characterize our generation are the aging of the population. Aging results in a progressive loss of muscle mass and strength called sarcopenia, which is Greek for 'poverty of flesh'. Sarcopenia could lead to functional impairment, physical disability, and even mortality. Today, sarcopenia is a matter of immense public concern for aging prevention. Its prevalence continues to rise, probably as a result of increasing elderly populations all over the world. This paper addressed the definition and epidemiology of sarcopenia and its underlying pathophysiology. In addition, we summarized the abundant information available in the literature related to sarcopenia, together with results from Korean sarcopenic obesity study (KSOS) that we performed.

Multifunctional Magneto‐Polymeric Nanohybrids for Targeted Detection and Synergistic Therapeutic Effects on Breast Cancer

Abstract: High-resolution molecular and cellular imaging is one of the most promising applications of nanoparticles, and a number of nanostructured materials, especially of cadmium-containing II–VI semiconductors, have been developed to suit this purpose. Recently, it was demonstrated that magnetic nanoparticles can be utilized as excellent magnetic resonance imaging (MRI) probes for noninvasive in vivo monitoring of molecular and cellular events. We recognized the presence of a number of biocompatible polymers suitable for targeted drug delivery and came upon an idea to combine the magnetic nanocrystals as ultrasensitive MR contrast agents, anticancer drugs as chemotherapeutic agents, and biodegradable amphiphilic block copolymers as stabilizers into a multifunctional hybrid nanosystem. The prepared multifunctional magneto-polymeric nanohybrids (MMPNs) further modified by antibodies would seek cancerous parts and allow simultaneous MR imaging and treatment (Scheme 1). Herein, we report a novel protocol for the preparation of MMPNs and characterization to evaluate the sensitivity and stability of prepared nanohybrids. Furthermore, targeted detection ability by MRI and synergistic tumoricidal efficacy on breast cancer cells were investigated for cellular and animal models. Monodispersed magnetic nanocrystals, soluble in organic solvents, were synthesized as reported (Figure 1a,b). To obtain the required water solubility, the hydrophobic nanocrystals and anticancer drug (doxorubicin, DOX) were simultaneously encapsulated with the amphiphilic block copolymer by a nanoemulsion method to give MMPNs. The structures of MMPNs examined by TEM are shown in Figure 1c,d, and the sizes of the MMPNs are consistent with the results from laser scattering: 69.7 8.7 nm (MnFe2O4) and 72.8 9.3 nm (Fe3O4), respectively (see the Supporting Scheme 1. Schematic illustration for the fabrication of MMPNs.