Showing papers by "Korea University published in 2009"

Efficacy and safety of sorafenib in patients in the Asia-Pacific region with advanced hepatocellular carcinoma: a phase III randomised, double-blind, placebo-controlled trial.

Abstract: Summary Background Most cases of hepatocellular carcinoma occur in the Asia-Pacific region, where chronic hepatitis B infection is an important aetiological factor. Assessing the efficacy and safety of new therapeutic options in an Asia-Pacific population is thus important. We did a multinational phase III, randomised, double-blind, placebo-controlled trial to assess the efficacy and safety of sorafenib in patients from the Asia-Pacific region with advanced (unresectable or metastatic) hepatocellular carcinoma. Methods Between Sept 20, 2005, and Jan 31, 2007, patients with hepatocellular carcinoma who had not received previous systemic therapy and had Child-Pugh liver function class A, were randomly assigned to receive either oral sorafenib (400 mg) or placebo twice daily in 6-week cycles, with efficacy measured at the end of each 6-week period. Eligible patients were stratified by the presence or absence of macroscopic vascular invasion or extrahepatic spread (or both), Eastern Cooperative Oncology Group performance status, and geographical region. Randomisation was done centrally and in a 2:1 ratio by means of an interactive voice-response system. There was no predefined primary endpoint; overall survival, time to progression (TTP), time to symptomatic progression (TTSP), disease control rate (DCR), and safety were assessed. Efficacy analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00492752. Findings 271 patients from 23 centres in China, South Korea, and Taiwan were enrolled in the study. Of these, 226 patients were randomly assigned to the experimental group (n=150) or to the placebo group (n=76). Median overall survival was 6·5 months (95% CI 5·56–7·56) in patients treated with sorafenib, compared with 4·2 months (3·75–5·46) in those who received placebo (hazard ratio [HR] 0·68 [95% CI 0·50–0·93]; p=0·014). Median TTP was 2·8 months (2·63–3·58) in the sorafenib group compared with 1·4 months (1·35–1·55) in the placebo group (HR 0·57 [0·42–0·79]; p=0·0005). The most frequently reported grade 3/4 drug-related adverse events in the 149 assessable patients treated with sorafenib were hand-foot skin reaction (HFSR; 16 patients [10·7%]), diarrhoea (nine patients [6·0%]), and fatigue (five patients [3·4%]). The most common adverse events resulting in dose reductions were HFSR (17 patients [11·4%]) and diarrhoea (11 patients [7·4%]); these adverse events rarely led to discontinuation. Interpretation Sorafenib is effective for the treatment of advanced hepatocellular carcinoma in patients from the Asia-Pacific region, and is well tolerated. Taken together with data from the Sorafenib Hepatocellular Carcinoma Assessment Randomised Protocol (SHARP) trial, sorafenib seems to be an appropriate option for the treatment of advanced hepatocellular carcinoma. Funding Bayer HealthCare Pharmaceuticals and Onyx Pharmaceuticals, Inc.

A DNA barcode for land plants.

Abstract: DNA barcoding involves sequencing a standard region of DNA as a tool for species identification. However, there has been no agreement on which region(s) should be used for barcoding land plants. To provide a community recommendation on a standard plant barcode, we have compared the performance of 7 leading candidate plastid DNA regions (atpF–atpH spacer, matK gene, rbcL gene, rpoB gene, rpoC1 gene, psbK–psbI spacer, and trnH–psbA spacer). Based on assessments of recoverability, sequence quality, and levels of species discrimination, we recommend the 2-locus combination of rbcL+matK as the plant barcode. This core 2-locus barcode will provide a universal framework for the routine use of DNA sequence data to identify specimens and contribute toward the discovery of overlooked species of land plants.

Gas sensors using hierarchical and hollow oxide nanostructures: Overview

Abstract: Hierarchical and hollow oxide nanostructures are very promising gas sensor materials due to their high surface area and well-aligned nanoporous structures with a less agglomerated configurations. Various synthetic strategies to prepare such hierarchical and hollow structures for gas sensor applications are reviewed and the principle parameters and mechanisms to enhance the gas sensing characteristics are investigated. The literature data clearly show that hierarchical and hollow nanostructures increase both the gas response and response speed simultaneously and substantially. This can be explained by the rapid and effective gas diffusion toward the entire sensing surfaces via the porous structures. Finally, the impact of highly sensitive and fast responding gas sensors using hierarchical and hollow nanostructures on future research directions is discussed.

User Awareness of Security Countermeasures and Its Impact on Information Systems Misuse: A Deterrence Approach

Abstract: Intentional insider misuse of information systems resources (i.e., IS misuse) represents a significant threat to organizations. For example, industry statistics suggest that between 50%--75% of security incidents originate from within an organization. Because of the large number of misuse incidents, it has become important to understand how to reduce such behavior. General deterrence theory suggests that certain controls can serve as deterrent mechanisms by increasing the perceived threat of punishment for IS misuse. This paper presents an extended deterrence theory model that combines work from criminology, social psychology, and information systems. The model posits that user awareness of security countermeasures directly influences the perceived certainty and severity of organizational sanctions associated with IS misuse, which leads to reduced IS misuse intention. The model is then tested on 269 computer users from eight different companies. The results suggest that three practices deter IS misuse: user awareness of security policies; security education, training, and awareness (SETA) programs; and computer monitoring. The results also suggest that perceived severity of sanctions is more effective in reducing IS misuse than certainty of sanctions. Further, there is evidence that the impact of sanction perceptions vary based on one's level of morality. Implications for the research and practice of IS security are discussed.

Coumarin-Derived Cu2+-Selective Fluorescence Sensor: Synthesis, Mechanisms, and Applications in Living Cells

Abstract: A novel coumarin-based fluorogenic probe bearing the 2-picolyl unit (1) was developed as a fluorescent chemosensor with high selectivity and suitable affinity in biological systems toward Cu2+ over other cations tested. The fluorescence on−off mechanism was studied by femtosecond time-resolved fluorescence (TRF) upconversion technique and ab initio calculations. The receptor can be applied to the monitoring of Cu2+ ion in aqueous solution with a pH span 4−10. To confirm the suitability of 1 for biological applications, we also employed it for the fluorescence detection of the changes of intracellular Cu2+ in cultured cells. The results indicate that 1 should be useful for the fluorescence microscopic imaging and the study on the biological functions of Cu2+.

A large-scale genome-wide association study of Asian populations uncovers genetic factors influencing eight quantitative traits.

Abstract: To identify genetic factors influencing quantitative traits of biomedical importance, we conducted a genome-wide association study in 8,842 samples from population-based cohorts recruited in Korea. For height and body mass index, most variants detected overlapped those reported in European samples. For the other traits examined, replication of promising GWAS signals in 7,861 independent Korean samples identified six previously unknown loci. For pulse rate, signals reaching genome-wide significance mapped to chromosomes 1q32 (rs12731740, P = 2.9 x 10(-9)) and 6q22 (rs12110693, P = 1.6 x 10(-9)), with the latter approximately 400 kb from the coding sequence of GJA1. For systolic blood pressure, the most compelling association involved chromosome 12q21 and variants near the ATP2B1 gene (rs17249754, P = 1.3 x 10(-7)). For waist-hip ratio, variants on chromosome 12q24 (rs2074356, P = 7.8 x 10(-12)) showed convincing associations, although no regional transcript has strong biological candidacy. Finally, we identified two loci influencing bone mineral density at multiple sites. On chromosome 7q31, rs7776725 (within the FAM3C gene) was associated with bone density at the radius (P = 1.0 x 10(-11)), tibia (P = 1.6 x 10(-6)) and heel (P = 1.9 x 10(-10)). On chromosome 7p14, rs1721400 (mapping close to SFRP4, a frizzled protein gene) showed consistent associations at the same three sites (P = 2.2 x 10(-3), P = 1.4 x 10(-7) and P = 6.0 x 10(-4), respectively). This large-scale GWA analysis of well-characterized Korean population-based samples highlights previously unknown biological pathways.

A benchmark study on the thermal conductivity of nanofluids

Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

An empirical framework for binary interactome mapping

Abstract: Several attempts have been made to systematically map protein-protein interaction, or 'interactome', networks. However, it remains difficult to assess the quality and coverage of existing data sets. Here we describe a framework that uses an empirically-based approach to rigorously dissect quality parameters of currently available human interactome maps. Our results indicate that high-throughput yeast two-hybrid (HT-Y2H) interactions for human proteins are more precise than literature-curated interactions supported by a single publication, suggesting that HT-Y2H is suitable to map a significant portion of the human interactome. We estimate that the human interactome contains approximately 130,000 binary interactions, most of which remain to be mapped. Similar to estimates of DNA sequence data quality and genome size early in the Human Genome Project, estimates of protein interaction data quality and interactome size are crucial to establish the magnitude of the task of comprehensive human interactome mapping and to elucidate a path toward this goal.

Reversible Watermarking Algorithm Using Sorting and Prediction

Abstract: This paper presents a reversible or lossless watermarking algorithm for images without using a location map in most cases. This algorithm employs prediction errors to embed data into an image. A sorting technique is used to record the prediction errors based on magnitude of its local variance. Using sorted prediction errors and, if needed, though rarely, a reduced size location map allows us to embed more data into the image with less distortion. The performance of the proposed reversible watermarking scheme is evaluated using different images and compared with four methods: those of Kamstra and Heijmans, Thodi and Rodriguez, and Lee et al. The results clearly indicate that the proposed scheme can embed more data with less distortion.

Short-Sale Strategies and Return Predictability

Abstract: We examine short selling in US stocks based on new SEC-mandated data for 2005. There is atremendousamountofshortsellinginoursample: shortsales represent24%ofNYSE and 31% of Nasdaq share volume. Short sellers increase their trading following positive returns and they correctly predict future negative abnormal returns. These patterns are robust to controlling for voluntary liquidity provision and for opportunistic risk-bearing by short sellers. The results are consistent with short sellers trading on short-term overreaction of stock prices. A trading strategy based on daily short-selling activity generates significant positive returns during the sample period. (JEL G12, G14)

Block copolymer nanolithography: translation of molecular level control to nanoscale patterns

Abstract: The self-asembly of block copolymers is a promising platform for the "bottom-up" fabrication of nanostructured materials and devices. This review covers some of the advances made in this field from the laboratory setting to applications where block copolymers are in use.

Nonblinking and Nonbleaching Upconverting Nanoparticles as an Optical Imaging Nanoprobe and T1 Magnetic Resonance Imaging Contrast Agent

Abstract: M M U N I Nonblinking and Nonbleaching Upconverting Nanoparticles as an Optical Imaging Nanoprobe and T1 Magnetic Resonance Imaging Contrast Agent C A T IO N By Yong Il Park, Jeong Hyun Kim, Kang Taek Lee, Ki-Seok Jeon, Hyon Bin Na, Jung Ho Yu, Hyung Min Kim, Nohyun Lee, Seung Hong Choi, Sung-Il Baik, Hyoungsu Kim, Seung Pyo Park, Beom-Jin Park, Young Woon Kim, Sung Ho Lee, Soo-Young Yoon, In Chan Song, Woo Kyung Moon, Yung Doug Suh,* and Taeghwan Hyeon*

Managing diversity and enhancing team outcomes: the promise of transformational leadership.

Abstract: In a sample of 62 research and development (R&D) teams, the authors examined transformational leadership as a moderator of the relationship of age, nationality, and educational background diversity with team outcomes. When levels of transformational leadership were high, nationality and educational diversity were positively related to team leaders' longitudinal ratings of team performance. These relationships were nonsignificant when transformational leadership was low. Age diversity was not related to team performance when transformational leadership was high, and it was negatively related to team performance when transformational leadership was low. Two mediated moderation effects help explain these findings. Transformational leadership moderated the relationship of the 3 examined diversity dimensions with the elaboration of task-relevant information, which in turn was positively associated with team performance. Moreover, transformational leadership moderated the relationship of the 3 diversity types with collective team identification, which in turn was positively related to the elaboration of task-relevant information. The authors discuss the theoretical and practical implications of these results. Overall, this study suggests that transformational leadership can foster the utilization of the potential, but frequently untapped, benefits entailed by both demographic and informational/cognitive team diversity. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

Two-photon probes for intracellular free metal ions, acidic vesicles, and lipid rafts in live tissues.

Abstract: Optical imaging with fluorescence microscopy is a vital tool in the study of living systems. The most common method for cell imaging, one-photon microscopy (OPM), uses a single photon of higher energy to excite the fluorophore. However, two-photon microscopy (TPM), which uses two photons of lower energy as the excitation source, is growing in popularity among biologists because of several distinct advantages. Using TPM, researchers can image intact tissue for a long period of time with minimum interference from tissue preparation artifacts, self-absorption, autofluorescence, photobleaching, and photodamage. However, to make TPM a more versatile tool in biology, researchers need a wider variety of two-photon probes for specific applications. In this Account, we describe a series of two-photon probes that we developed that can visualize the distribution of intracellular metal ions, acidic vesicles, and lipid rafts in living cells and tissues. The development of these probes requires a significant two-photon cross section for the bright image and receptors (sensing moieties) that triggers the emission of the two-photon excited fluorescence upon binding with the ions or membrane in the living system. These probes also must be sensitive to the polarity of the environment to allow selective detection of cytosolic and membrane-bound probes. In addition, they need to be cell-permeable, water-soluble for the staining of cells and tissues, and highly photostable for long-term imaging. The resulting probes-AMg1 (Mg(2+)), ACa1-ACa3 (Ca(2+)), AZn1 and AZn2 (Zn(2+)), AH1, AH2, and AL1 (acidic vesicles), and CL2 (membrane)-use 2-acetyl-6-aminonaphthalene as the fluorophore and receptors for the target ions or membrane. All of these two-photon turn-on probes can detect the intracellular free metal ions, acidic vesicles, and lipid rafts at 100-300 microm depth in live tissues. Moreover, with ACa1-AM, we could simultaneously visualize the spontaneous Ca(2+) waves in the somas of neurons and astrocytes at approximately 120 microm depth in fresh hypothalamic slices for more than 1000 s without appreciable decay. Furthermore, AL1 could visualize the transport of the acidic vesicles between cell body and axon terminal along the axon in fresh rat hippocampal slices at approximately 120 microm depth.

When and how diversity benefits teams: the importance of team members' need for cognition

Abstract: In a study of 83 teams from eight organizations, we examined team need for cognition—the tendency to engage in and enjoy effortful cognitive endeavors—as a moderator of the relationships between both age diversity and educational specialization diversity, and elaboration of task-relevant information, collective team identification and, ultimately, team performance. Age and educational diversity were positively related to these outcomes when team need for cognition was high, rather than low. Both the elaboration of task-relevant information and collective team identification mediated a moderating effect of need for cognition on the relationship between both types of diversity and team performance.

Terahertz field enhancement by a metallic nano slit operating beyond the skin-depth limit

Abstract: The effect of a tiny gap in a metal substrate on incident terahertz radiation in the regime where the gap's dimensions are smaller than the metal's skin-depth are investigated. The results and theoretical analysis show that the gap acts as a capacitor charged by light-induced currents, and dramatically enhances the local electric field.

Value Relevance of FAS 157 Fair Value Hierarchy Information and the Impact of Corporate Governance Mechanisms

Abstract: Statement of Financial Accounting Standards No. 157 (FAS 157), Fair Value Measurements, prioritizes the source of information used in fair value measurements into three levels: (1) Level 1 (observable inputs from quoted prices in active markets), (2) Level 2 (indirectly observable inputs from quoted prices of comparable items in active markets, identical items in inactive markets, or other market-related information), and (3) Level 3 (unobservable, firm-generated inputs). Using quarterly reports of banking firms in 2008, we find that the value relevance of Level 1 and Level 2 fair values is greater than the value relevance of Level 3 fair values. In addition, we find evidence that the value relevance of fair values (especially Level 3 fair values) is greater for firms with strong corporate governance. Overall, our results support the relevance of fair value measurements under FAS 157, but weaker corporate governance mechanisms may reduce the relevance of these measures.

Measurement of the differential branching fraction and forward-backward asymmetry for B --> K(*)l+l-.

Abstract: We study B -> Kd(*)l(+)l(-) decays (l = e,u) based on a data sample of 657 x 10(6) B (B) over bar pairs collected with the Belle detector at the KEKB e(+)e(-) collider. We report the differential branching fraction, isospin asymmetry, K* polarization, and the forward-backward asymmetry (A(FB)) as functions of q(2) = M(ll)(2)c(2). The fitted A(FB) spectrum exceeds the standard model expectation by 2.7 standard deviations. The measured branching fractions are B(B -> K*l(+)l(-)) = (10: 7(-1.0)(+1.1)) x 10(-7) and B(B -> Kl(+)l(-)) = (4.8 (+0.5)(-0.4) +/- 0.3) x 10(-7), where the first errors are statistical and the second are systematic, with the muon to electron ratios R-K* = 0.83 +/- 0: 17 +/- 0.08 and R-K = 1.03 +/- 0.19 +/- 0.06.

Faces and text attract gaze independent of the task: Experimental data and computer model.

Abstract: Previous studies of eye gaze have shown that when looking at images containing human faces, observers tend to rapidly focus on the facial regions. But is this true of other high-level image features as well? We here investigate the extent to which natural scenes containing faces, text elements, and cell phones - as a suitable control - attract attention by tracking the eye movements of subjects in two types of tasks - free viewing and search. We observed that subjects in free-viewing conditions look at faces and text 16.6 and 11.1 times more than similar regions normalized for size and position of the face and text. In terms of attracting gaze, text is almost as effective as faces. Furthermore, it is difficult to avoid looking at faces and text even when doing so imposes a cost. We also found that subjects took longer in making their initial saccade when they were told to avoid faces/text and their saccades landed on a non-face/non-text object. We refine a well-known bottom–up computer model of saliency-driven attention that includes conspicuity maps for color, orientation, and intensity by adding high-level semantic information (i.e., the location of faces or text) and demonstrate that this significantly improves the ability to predict eye fixations in natural images. Our enhanced model’s predictions yield an area under the ROC curve over 84% for images that contain faces or text when compared against the actual fixation pattern of subjects. This suggests that the primate visual system allocates attention using such an enhanced saliency map.

The Safety of Objects: Materialism, Existential Insecurity, and Brand Connection

Abstract: Over the past 2 decades, a large body of research has examined how materialism is formed and how this value influences well-being. Although these studies have substantially contributed to our understanding of materialism, they shed little light on this value's relationship to consumer behavior. Our research seeks to address this gap by examining the influence of materialism on self- and communal-brand connections. We ground our conceptualization in terror management theory and suggest that materialistic individuals form strong connections to their brands as a response to existential insecurity. We test this premise by conducting a national survey among 314 adults as well as an experiment among 125 college students. Our results provide broad support for our thesis and suggest that the fear of death encourages materialistic individuals to form strong connections with their brands.

Epigallocatechin-3-gallate, a histone acetyltransferase inhibitor, inhibits EBV-induced B lymphocyte transformation via suppression of RelA acetylation.

Abstract: Because the p300/CBP-mediated hyperacetylation of RelA (p65) is critical for nuclear factor-kappaB (NF-kappaB) activation, the attenuation of p65 acetylation is a potential molecular target for the prevention of chronic inflammation. During our ongoing screening study to identify natural compounds with histone acetyltransferase inhibitor (HATi) activity, we identified epigallocatechin-3-gallate (EGCG) as a novel HATi with global specificity for the majority of HAT enzymes but with no activity toward epigenetic enzymes including HDAC, SIRT1, and HMTase. At a dose of 100 micromol/L, EGCG abrogates p300-induced p65 acetylation in vitro and in vivo, increases the level of cytosolic IkappaBalpha, and suppresses tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB activation. We also showed that EGCG prevents TNFalpha-induced p65 translocation to the nucleus, confirming that hyperacetylation is critical for NF-kappaB translocation as well as activity. Furthermore, EGCG treatment inhibited the acetylation of p65 and the expression of NF-kappaB target genes in response to diverse stimuli. Finally, EGCG reduced the binding of p300 to the promoter region of interleukin-6 gene with an increased recruitment of HDAC3, which highlights the importance of the balance between HATs and histone deacetylases in the NF-kappaB-mediated inflammatory signaling pathway. Importantly, EGCG at 50 micromol/L dose completely blocks EBV infection-induced cytokine expression and subsequently the EBV-induced B lymphocyte transformation. These results show the crucial role of acetylation in the development of inflammatory-related diseases.

Group-Based Trust Management Scheme for Clustered Wireless Sensor Networks

Abstract: Traditional trust management schemes developed for wired and wireless ad hoc networks are not well suited for sensor networks due to their higher consumption of resources such as memory and power. In this work, we propose a new lightweight group-based trust management scheme (GTMS) for wireless sensor networks, which employs clustering. Our approach reduces the cost of trust evaluation. Also, theoretical as well as simulation results show that our scheme demands less memory, energy, and communication overheads as compared to the current state-of-the-art trust management schemes and it is more suitable for large-scale sensor networks. Furthermore, GTMS also enables us to detect and prevent malicious, selfish, and faulty nodes.