Hyo Won Kim

Caffeinated coffee, decaffeinated coffee, and the phenolic phytochemical chlorogenic acid up-regulate NQO1 expression and prevent H2O2-induced apoptosis in primary cortical neurons

Neurodegenerative disorders are strongly associated with oxidative stress, which is induced by reactive oxygen species including hydrogen peroxide (H₂O₂). Epidemiological studies have suggested that coffee may be neuroprotective, but the molecular mechanisms underlying this effect have not been clarified. In this study, we investigated the protective effects of caffeinated coffee, decaffeinated coffee, and the phenolic phytochemical chlorogenic acid (5-O-caffeoylquinic acid), which is present in both caffeinated and decaffeinated coffee, against oxidative neuronal death. H₂O₂-induced apoptotic nuclear condensation in neuronal cells was strongly inhibited by pretreatment with caffeinated coffee, decaffeinated coffee, or chlorogenic acid. Pretreatment with caffeinated coffee, decaffeinated coffee, or chlorogenic acid inhibited the H₂O₂-induced down-regulation of anti-apoptotic proteins Bcl-2 and Bcl-X(L) while blocking H₂O₂-induced pro-apoptotic cleavage of caspase-3 and pro-poly(ADP-ribose) polymerase. We also found that caffeinated coffee, decaffeinated coffee, and chlorogenic acid induced the expression of NADPH:quinine oxidoreductase 1 (NQO1) in neuronal cells, suggesting that these substances protect neurons from H₂O₂-induced apoptosis by up-regulation of this antioxidant enzyme. The neuroprotective efficacy of caffeinated coffee was similar to that of decaffeinated coffee, indicating that active compounds present in both caffeinated and decaffeinated coffee, such as chlorogenic acid, may drive the effects.

The prevalence of specific phobia and associated co-morbid features in children and adolescents.

OBJECTIVEnThe aims of this study were to investigate the prevalence, associated co-morbid psychiatric disorders and behavioral/emotional problems associated with the subtypes of specific phobia in children and adolescents.nnnMETHODSnA total of 2673 randomly selected children and adolescents from Seoul, Korea were assessed using the parent version of the Diagnostic Interview Schedule for Children (DISC-IV) and Childrens Behavior Checklist (CBCL). We analyzed differences in psychiatric co-morbidities and CBCL profiles among the subtypes of specific phobia.nnnRESULTSnThe 1-year prevalence of specific phobia was 7.9% (95% CI 7.63-8.17). Animal phobia was associated with anxiety disorder (OR 8.68, 95% CI 1.91-39.51) and oppositional defiant disorder (OR 2.55, 95% CI 1.27-5.12). Nature-environment phobia was associated with anxiety disorder (OR 25.70, 95% CI 6.16-107.10). Blood-injection-injury phobia showed associations with attention-deficit/hyperactivity disorder (ADHD: OR 6.74, 95% CI 2.81-16.15). Subjects with nature-environment phobia scored higher than did controls on the anxious/depressed, social problems, attention problems, and total behavioral problem profiles of the CBCL. Subjects with blood-injection-injury phobia scored significantly higher than did controls on the attention problems, aggressive behaviors, and externalizing problem profiles.nnnCONCLUSIONSnContrary to animal phobias, nature-environment and blood-injection-injury phobias were associated with various behavioral and emotional problems and approximately correlated to their co-morbid psychiatric disorders. Among these subtypes, significant differences were found in demographic characteristics, co-morbid psychiatric disorders, and emotional/behavioral problems. These findings suggest that distinctive clinical characteristics might be related with different subtypes of specific phobia and clinician must consider psychiatric co-morbidities when treating children & adolescents with specific phobia.

Nanoscale control of phonon excitations in graphene

Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realising graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron–phonon excitations, further influencing phonon-assisted inelastic electron tunnelling.

Water scarcity hotspots travel downstream due to human interventions in the 20th and 21st century

Water scarcity is rapidly increasing in many regions. In a novel, multi-model assessment, we examine how human interventions (HI: land use and land cover change, man-made reservoirs and human water use) affected monthly river water availability and water scarcity over the period 1971–2010. Here we show that HI drastically change the critical dimensions of water scarcity, aggravating water scarcity for 8.8% (7.4–16.5%) of the global population but alleviating it for another 8.3% (6.4–15.8%). Positive impacts of HI mostly occur upstream, whereas HI aggravate water scarcity downstream; HI cause water scarcity to travel downstream. Attribution of water scarcity changes to HI components is complex and varies among the hydrological models. Seasonal variation in impacts and dominant HI components is also substantial. A thorough consideration of the spatially and temporally varying interactions among HI components and of uncertainties is therefore crucial for the success of water scarcity adaptation by HI.

Atomic and electronic structure of an alloyed topological insulator, Bi1.5Sb0.5Te1.7Se1.3.

Bi2−xSbxTe3−ySey has been argued to exhibit both topological surface states and insulating bulk states, but has not yet been studied with local probes on the atomic scale. Here we report on the atomic and electronic structures of Bi1.5Sb0.5Te1.7Se1.3 studied using scanning tunnelling microscopy (STM) and spectroscopy (STS). Although there is significant surface disorder due to alloying of constituent atoms, cleaved surfaces of the crystals present a well-ordered hexagonal lattice with 10 Å high quintuple layer steps. STS results reflect the band structure and indicate that the surface state and Fermi energy are both located inside the energy gap. In particular, quasi-particle interference patterns from electron scattering demonstrate that the surface states possess linear dispersion and chirality from spin texture, thus verifying its topological nature. This finding demonstrates that alloying is a promising route to achieve full suppression of bulk conduction in topological insulators whilst keeping the topological surface state intact.

One-dimensional molecular zippers.

We synthesized an azobenzene derivative to demonstrate a one-dimensional molecular zipper. The formation and underlying mechanism of the molecular zipper formed by combined hydrogen-bonding and van der Waals interactions between adjacent molecules were investigated on a Au(111) surface using scanning tunneling microscopy and density functional theory calculations.

3,3′-Diindolylmethane Inhibits Lipopolysaccharide-Induced Microglial Hyperactivation and Attenuates Brain Inflammation

Recent studies have revealed that microglial hyperactivation and neuroinflammation are implicated in development and progression of neurodegenerative diseases. In this study, we examined the beneficial effects of 3,3-diindolylmethane (DIM) and indole-3-carbinol (I3C), dietary components found in cruciferous vegetables, on brain inflammation. DIM, a major metabolite of I3C, suppressed lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase and cyclooxygenase-2 in BV-2 microglia, but I3C did not. DIM, but not I3C, attenuated DNA-binding activity of nuclear factor-κB (NF-κB) and phosphorylation of inhibitor of κB, suggesting that DIM might inhibit microglial hyperactivation by attenuating inflammatory transcription factor NF-κB. In addition, DIM, but not I3C, protected primary cortical neurons from inflammatory toxicity induced by the conditioned media from LPS-stimulated BV-2 microglia, indicating that DIM might attenuate microglial hyperactivation-mediated neuronal death. In an in vivo model of neuroinflammation, DIM suppressed LPS-induced brain inflammation in mouse hippocampus, as determined by the number of Iba-1-positive cells and the mRNA expression of F4/80. Taken together, these results suggest that DIM may have beneficial potential against brain inflammation and neurodegenerative diseases through the negative regulation of the NF-κB signal pathway in microglia.

Physisorbed-precursor-assisted atomic layer deposition of reliable ultrathin dielectric films on inert graphene surfaces for low-power electronics

Among the most fundamental challenges encountered in the successful incorporation of graphene in silicon-based electronics is the conformal growth of ultrathin dielectric films, especially those with thicknesses lower than 5 nm, on chemically inert graphene surfaces. Here, we present physisorbed-precursor-assisted atomic layer deposition (pALD) as an extremely robust method for fabricating such films. Using atomic-scale characterisation, it is confirmed that conformal and intact ultrathin Al2O3 films can be synthesised on graphene by pALD. The mechanism underlying the pALD process is identified through first-principles calculations based on density functional theory. Further, this novel deposition technique is used to fabricate two types of wafer-scale devices. It is found that the incorporation of a 5 nm-thick pALD Al2O3 gate dielectric film improves the performance of metal-oxide-graphene field-effect transistors to a greater extent than does the incorporation of a conventional ALD Al2O3 film. We also employ a 5 nm-thick pALD HfO2 film as a highly scalable dielectric layer with a capacitance equivalent oxide thickness of 1 nm in graphene-based tunnelling field-effect transistors fabricated on a glass wafer and achieve a subthreshold swing of 30 mV/dec. This significant improvement in switching allows for the low-voltage operation of an inverter within 0.5 V of both the drain and the gate voltages, thus paving the way for low-power electronics.

THE ASIAN DUST EVENTS AND HOSPITAL ADMISSIONS WITH RESPIRATORY AND CARDIOVASCULAR DISEASE IN SEOUL, KOREA: ISEE-249

The Korean peninsula has a long history of spring time dust clouds blown by winds from the arid deserts of Mongolia and China, these are called Asian dust event. During the episode in 2002, daily average of PM10 in Seoul exceeded 600 mg/m3. Public concern about the possible adverse effects of these dust events has increased, because the dust arrives in Korea after having passed over heavily industrialized eastern China. This study was planned to investigate the association between the episode of the Asian dust and hospital admissions with respiratory and cardiovascular disease in Seoul, Korea. We constructed daily counts of all admissions for respiratory disease (ICD-10 codes J00–J99) and cardiovascular disease (ICD-10 codes I00–I99) in Seoul during the period of 2000 through 2002. A generalized linear model with a log-link and a Poisson distribution were used to examine the relation of Asian dust events to hospital admissions, adjusting for weather variables and time trends of admission counts. To accommodate delayed effects of Asian dust events, we fitted the model with 7-day moving averages of admission counts. The estimated relative risk of hospitalization for respiratory disease for the Asian dust events was 1.00 (95% confidence interval [CI] = 0.96–1.03) and the risk for cardiovascular disease was 0.99 (95% CI = 0.96–1.02). Our results indicate that the Asian dust events experienced in Seoul has little effect on the hospitalization for respiratory and cardiovascular disease in general. Acknowledgement: this study was supported by the Ministry of Environment, Republic of Korea (Eco-technopia 2002).

Local potential fluctuation of topological surface states in Bi1.5Sb0.5Te1.7Se1.3 observed by Landau level spectroscopy

We report the local observation of the band structure of topological surface states in Bi1.5Sb0.5Te1.7Se1.3 using scanning tunneling microscopy/spectroscopy (STM/STS). The energy-momentum dispersion relation is locally deduced by extracting the Landau level (LL) energies, which are formed in a high magnetic field, from the STS data. Spatial variation of LLs revealed a shift of the Dirac point energy at the nanometer scale. The structure of the potential fluctuation was not correlated with the topography, which indicated that the Te/Se substitution did not induce the potential shift because of their same valence. The results show that disorders from the Te/Se substitution at the surface do not induce any localized charged states and do not affect topological surface states.