Showing papers by "Hong Kong Baptist University published in 2009"

The Graph Neural Network Model

Abstract: Many underlying relationships among data in several areas of science and engineering, e.g., computer vision, molecular chemistry, molecular biology, pattern recognition, and data mining, can be represented in terms of graphs. In this paper, we propose a new neural network model, called graph neural network (GNN) model, that extends existing neural network methods for processing the data represented in graph domains. This GNN model, which can directly process most of the practically useful types of graphs, e.g., acyclic, cyclic, directed, and undirected, implements a function tau(G,n) isin IRm that maps a graph G and one of its nodes n into an m-dimensional Euclidean space. A supervised learning algorithm is derived to estimate the parameters of the proposed GNN model. The computational cost of the proposed algorithm is also considered. Some experimental results are shown to validate the proposed learning algorithm, and to demonstrate its generalization capabilities.

Functional metallophosphors for effective charge carrier injection/transport: New robust OLED materials with emerging applications

Abstract: Organic light-emitting diodes (OLEDs) show great promise of revolutionizing display technologies in the scientific community. One successful approach for improved device efficiency has been to maximize the electron-hole recombination using dopants that emit from the triplet excited state. In this context, heavy transition metal complexes have recently gained tremendous academic and industrial research interest for fabricating highly efficient phosphorescent OLEDs by taking advantage of the 1:3 exciton singlet/triplet ratio predicted by simple spin statistics. Traditional room-temperature phosphorescent dyes are monofunctional materials working only as light-emitting centres but other key issues including charge generation and transport remain to be addressed in the electroluminescence. This Feature Article highlights recent and current advances in developing new synthetic strategies for multifunctional organometallic phosphors, which integrate both luminescent and charge carrier injection/transport functions into the same molecules so that they perform most, if not all, of the necessary functional roles (viz. photoexcitation, charge injection and transport as well as recombination) for achieving high-efficiency devices. Considerable focus is placed on the design concepts towards the tuning capability of charge-transport characteristics and phosphorescence emission colour of this prominent class of metallophosphors. In particular, the latest research endeavor in accomplishing novel triplet emitters with enhanced charge injection/charge transport of both hole and electron carriers is criticially discussed, which can provide good implications regarding their possible routes for future research development in the field.

Large area, continuous, few-layered graphene as anodes in organic photovoltaic devices

Abstract: Large-area, continuous, transparent, and highly conducting few-layered graphene films produced by chemical vapor deposition method were used as anode for application in photovoltaic devices. The noncovalent modification of the graphene films with pyrene buanoic acid succidymidyl ester improved the power conversion efficiency (PCE) to 1.71%. This performance corresponds to ∼55.2% of the PCE of a control device based on indium tin oxide (ITO)/poly(3,4–ethylenedioxythiophene):poly(styrenesulfonate)/poly(3-hexyl)thiophene: phenyl-C61-butyric acid methyl ester/LiF/Al electrodes (PCE=3.1%). This finding paves the way for the substitution of ITO in photovoltaic and electroluminescent devices with low cost graphene films.

The direct transformation of carbon dioxide to organic carbonates over heterogeneous catalysts

Abstract: In this review article, we report the recent developments of heterogeneous catalysts for the synthesis of cyclic and dimethyl carbonates from CO 2 through various routes. The synthesis of cyclic carbonates via cycloaddition of CO 2 to epoxides is one of the few processes that have been commercialized. Compared to the many effective homogeneous catalysts, the heterogeneous catalysts have the advantages of being superior in stability and reusability. However, of the reported catalysts including metal oxides, zeolites, smectite, supported organic bases, metal complexes, and ionic liquids, none can be considered as highly active and selective under mild conditions. Also, heterogeneous catalysts used in other routes do not perform satisfactorily. The supported ionic liquids have attracted much more attention and are worthy of further research for the cycloaddition reaction. We predict that the mechanisms of acid–base or electrophile–nucleophile catalysis proposed in the literature will be valuable for the design and fabrication of high-performance catalysts.

An Alternate Wetting and Moderate Soil Drying Regime Improves Root and Shoot Growth in Rice

Abstract: A major challenge in rice (Oryza sativa L.) production is to achieve the dual goal of increasing food production and saving water. This study aimed to investigate if alternate wetting and drying regimes could improve root and shoot growth and consequently increase grain yield and water use efficiency (WUE). Two rice varieties were field-grown at Yangzhou, China in 2005 and 2006. Three irrigation regimes, alternate wetting and moderate soil drying (WMD, re-watered when soil water potential reached -15 kPa at 15-20 cm depth), alternate wetting and severe soil drying (WSD, re-watered when soil water potential reached -30 kPa), and a conventional irrigation (Cl, continuously flooded), were imposed during the whole growing season. Compared with the Cl, the WMD regime significantly increased, whereas the WSD regime reduced, root oxidation activity, cytokinin concentrations in roots and shoots, leaf photosynthetic rate, and activities of key enzymes involved in sucrose-to-starch conversion in grains. Grain yield of the two varieties, on the average, was increased by 11% under the WMD regime, and was reduced by 32% under the WSD regime when compared with that under the Cl regime. Averaged WUE of the two varieties was increased by 55% under the WMD regime and 36% under the WSD regime. We conclude that a moderate wetting and drying regime can enhance root growth which benefits other physiological processes and result in higher grain yield and WUE.

Toward culture‐sensitive theories of the work–family interface

Abstract: Due to societal trends, managing the work–family interface has become an increasingly challenging task for employees in virtually every nation. However, prior studies of this interface have mostly tested U.S.-based theories using U.S. samples. The construct of societal or national culture, which seems likely to shape individuals' experiences of the work–family interface, has been generally unacknowledged in theories and research in the work–family literature. In this paper, we offer guidelines for the development of culture-sensitive theories of work–family phenomena and for research to test such theories as they are developed. First, we review the few prior research attempts that have incorporated cultural considerations in some manner and identify cultural dimensions that are likely to influence the work–family interface. Second, we demonstrate how selected cultural dimensions may be incorporated into theories of work–family conflict and enrichment, two constructs that represent the negative and positive side of the work–family interface respectively, to make these theories more culture-sensitive. Finally, we offer an ambitious agenda for future theory and research to increase understanding of cultural influences on the work–family interface. Copyright © 2009 John Wiley & Sons, Ltd.

Tunneling and Propping Up: An Analysis of Related Party Transactions by Chinese Listed Companies

Abstract: We examine a sample of related party transactions between Chinese publicly listed firms and their controlling shareholders during 2001-2002. Minority shareholders in these firms seem to be subject to expropriation through tunneling but also gain from propping up. On balance, there is more tunneling than propping. Both types of firms have larger state ownership compared to the rest of the Chinese market but firms that are propped up are larger and have larger state ownership than firms subject to tunneling. Propped up firms are more likely to have foreign shareholders and to be cross-listed abroad compared to firms that are subject to tunneling. Propped up firms also tend to have worse operating performance in the fiscal year preceding the announcement of the related party transaction. Finally, we find that related party transactions representing tunneling are accompanied by significantly less information disclosure compared to related party transactions representing propping.

Arbitrated quantum signature scheme using Bell states

Abstract: In an arbitrated quantum signature scheme, the signatory signs the message and the receiver verifies the signature's validity with the assistance of the arbitrator. We present an arbitrated quantum signature scheme using two-particle entangled Bell states similar to the previous scheme using three-particle entangled Greenberger-Horne-Zeilinger states [G. H. Zeng and C. H. Keitel, Phys. Rev. A 65, 042312 (2002)]. The proposed scheme can preserve the merits in the original scheme while providing a higher efficiency in transmission and reducing the complexity of implementation.

Computational Capabilities of Graph Neural Networks

Abstract: In this paper, we will consider the approximation properties of a recently introduced neural network model called graph neural network (GNN), which can be used to process-structured data inputs, e.g., acyclic graphs, cyclic graphs, and directed or undirected graphs. This class of neural networks implements a function tau(G, n) isin R m that maps a graph G and one of its nodes n onto an m-dimensional Euclidean space. We characterize the functions that can be approximated by GNNs, in probability, up to any prescribed degree of precision. This set contains the maps that satisfy a property called preservation of the unfolding equivalence, and includes most of the practically useful functions on graphs; the only known exception is when the input graph contains particular patterns of symmetries when unfolding equivalence may not be preserved. The result can be considered an extension of the universal approximation property established for the classic feedforward neural networks (FNNs). Some experimental examples are used to show the computational capabilities of the proposed model.

Enhancement of the applicability of markowitz's portfolio optimization by utilizing random matrix theory

Abstract: The traditional estimated return for the Markowitz mean-variance optimization has been demonstrated to seriously depart from its theoretic optimal return. We prove that this phenomenon is natural and the estimated optimal return is always √ γ times larger than its theoretic counterpart, where γ = 1 1−y with y as the ratio of the dimension to sample size. Thereafter, we develop new bootstrap-corrected estimations for the optimal return and its asset allocation and prove that these bootstrap-corrected estimates are proportionally consistent with their theoretic counterparts. Our theoretical results are further confirmed by our simulations, which show that the essence of the portfolio analysis problem could be adequately captured by our proposed approach. This greatly enhances the practical uses of the Markowitz mean-variance optimization procedure.

The Synthesis and One‐ and Two‐Photon Optical Properties of Dipolar, Quadrupolar and Octupolar Donor–Acceptor Molecules Containing Dimesitylboryl Groups

Abstract: Two series of related donor–acceptor conjugated dipolar, pseudo-quadrupolar (V-shaped) and octupolar molecular systems based on the p-dimesitylborylphenylethynylaniline core, namely, 4-(4-dimesitylborylphenylethynyl)-N,N-dimethylaniline, 4-[4-(4-dimesitylborylphenylethynyl)phenylethynyl]-N,N-dimethylaniline, 3,6-bis(4-dimesitylborylphenylethynyl)-N-n-butylcarbazole and tris[4-(4-dimesitylborylphenylethynyl)phenyl]amine, and on the E-p-dimesitylborylethenylaniline motif, namely, E-4-dimesitylborylethenyl-N,N-di(4-tolyl)aniline, 3,6-bis(E-dimesitylborylethenyl)-N-n-butylcarbazole and tris(E-4-dimesitylborylethenylphenyl)amine have been synthesised by palladium-catalyzed cross-coupling and hydroboration routes, respectively. Their absorption and emission maxima, fluorescence lifetimes and quantum yields have been obtained and their two-photon absorption (TPA) spectra and TPA cross-sections have been examined. Of these systems, the octupolar compound tris(E-4-dimesitylborylethenylphenyl)amine has been shown to exhibit the largest TPA cross-section among the two series of approximately 1000 GM at 740 nm. Its TPA performance is comparable to those of other triphenylamine-based octupoles of similar size. The combination of such large TPA cross-sections and high emission quantum yields, up to 0.94, make these systems attractive for applications involving two-photon excited fluorescence (TPEF).

Glucose-Induced Delay of Seed Germination in Rice is Mediated by the Suppression of ABA Catabolism Rather Than an Enhancement of ABA Biosynthesis

Abstract: Both glucose and ABA play crucial roles in the regulation of seed germination and post-germination development. In Arabidopsis thaliana , up-regulation of ABA biosynthesis is suggested as one of the possible mechanisms mediating the glucose-induced delay in seed germination. Since the endogenous ABA level is controlled by the equilibrium between ABA biosynthesis and catabolism, we investigated how this equilibrium is related to the regulation of seed germination by glucose in rice. When ABA biosynthesis was inhibited by nordihydroguaiaretic acid (NDGA), an inhibitor of the ABA anabolic enzyme 9- cis -epoxycarotenoid dioxygenase (NCED), rice seed germination showed no response. In contrast, inhibition of ABA catabolism by diniconazole signifi cantly arrested seed germination, suggesting that the regulation of ABA catabolism plays a major role. Further experiments indicated that the expression of OsABA8ox3 , a key gene in ABA catabolism and encoding ABA 8 ′ -hydroxylase in rice, was signifi cantly increased during the fi rst 6 h of imbibition, which was consistent with the decline of ABA content in the imbibed seeds. Expression of OsABA8ox genes, especially OsABA8ox2 and OsABA8ox3 , was sensitively suppressed in the presence of exogenously supplied glucose. In contrast, the expression profi les of OsNCED genes that control the limiting step of ABA biosynthesis showed no signifi cant changes in response to low levels of glucose. Our results demonstrated that the glucose-induced delay of seed germination is a result of the suppression of ABA catabolism rather than any enhancement of ABA biosynthesis during rice seed germination.

Randomized trials published in some Chinese journals: how many are randomized?

Abstract: The approximately 1100 medical journals now active in China are publishing a rapidly increasing number of research reports, including many studies identified by their authors as randomized controlled trials. It has been noticed that these reports mostly present positive results, and their quality and authenticity have consequently been called into question. We investigated the adequacy of randomization of clinical trials published in recent years in China to determine how many of them met acceptable standards for allocating participants to treatment groups. The China National Knowledge Infrastructure electronic database was searched for reports of randomized controlled trials on 20 common diseases published from January 1994 to June 2005. From this sample, a subset of trials that appeared to have used randomization methods was selected. Twenty-one investigators trained in the relevant knowledge, communication skills and quality control issues interviewed the original authors of these trials about the participant randomization methods and related quality-control features of their trials. From an initial sample of 37,313 articles identified in the China National Knowledge Infrastructure database, we found 3137 apparent randomized controlled trials. Of these, 1452 were studies of conventional medicine (published in 411 journals) and 1685 were studies of traditional Chinese medicine (published in 352 journals). Interviews with the authors of 2235 of these reports revealed that only 207 studies adhered to accepted methodology for randomization and could on those grounds be deemed authentic randomized controlled trials (6.8%, 95% confidence interval 5.9–7.7). There was no statistically significant difference in the rate of authenticity between randomized controlled trials of traditional interventions and those of conventional interventions. Randomized controlled trials conducted at hospitals affiliated to medical universities were more likely to be authentic than trials conducted at level 3 and level 2 hospitals (relative risk 1.58, 95% confidence interval 1.18–2.13, and relative risk 14.42, 95% confidence interval 9.40–22.10, respectively). The likelihood of authenticity was higher in level 3 hospitals than in level 2 hospitals (relative risk 9.32, 95% confidence interval 5.83–14.89). All randomized controlled trials of pre-market drug clinical trial were authentic by our criteria. Of the trials conducted at university-affiliated hospitals, 56.3% were authentic (95% confidence interval 32.0–81.0). Most reports of randomized controlled trials published in some Chinese journals lacked an adequate description of randomization. Similarly, most so called 'randomized controlled trials' were not real randomized controlled trials owing toa lack of adequate understanding on the part of the authors of rigorous clinical trial design. All randomized controlled trials of pre-market drug clinical trial included in this research were authentic. Randomized controlled trials conducted by authors in high level hospitals, especially in hospitals affiliated to medical universities had a higher rate of authenticity. That so many non-randomized controlled trials were published as randomized controlled trials reflected the fact that peer review needs to be improved and a good practice guide for peer review including how to identify the authenticity of the study urgently needs to be developed.

Relationship Between Anthropometric and Physiological Characteristics in Youth Soccer Players

Abstract: This study examined the relationship between anthropometric and physiological performances among youth soccer players and the positional differences for these variables. Seventy U14 male soccer players (goalkeeper: 10, defender: 20, midfielder: 25, and forward: 15) participated in this study. Body mass was significantly (p < 0.05) correlated with ball shooting speed (r = 0.58) and 30 m sprint time (r = -0.54). Body height was significantly (p < 0.05) correlated with vertical jump height (r = 0.36), 10 m (r = -0.32) and 30 m (r = -0.64) sprint times, Yo-Yo intermittent endurance run (YYIER) distance (r = 0.26), and running time during maximal oxygen uptake (Vo2max) (r = 0.35). Body mass index (BMI) was significantly (p < 0.05) correlated with ball shooting speed (r = 0.31), 30 m sprint time (r = -0.24), Hoff test dribble distance (r = -0.29), YYIER distance (r = -0.25), submaximal running cost (r = -0.38), Vo2max (r = -0.42), and the corresponding running time (r = -0.24). Significant positional differences were observed in anthropometry (body mass [p < 0.01], height [p < 0.01], and BMI [p < 0.01]) but not in physiological performances. This study provides a scientific rationale behind the coaches' practice of selecting young soccer players according to their anthropometry for short-term benefits such as heavier players for higher ball shooting speed and 30-m sprint ability as an example. However, this does not justify such practice in the long-term process of player development.

Understanding the role of gender in bloggers' switching behavior

Abstract: Blog has become an increasingly popular form of social networking technology in recent years. Many world famous web sites (e.g., Microsoft, Yahoo!, and Google) are providing blog services on the Internet. Bloggers, therefore, can easily establish and maintain their blogs through such services. However, research on blogs' adoption and diffusion is rare. In this study, we attempt to study bloggers' post-adoption behaviors. We examine bloggers' intention to switch their blog services by building upon studies in the marketing and IS literature. Particularly, the role of gender is explored and an online survey is conducted to test the research model. Findings confirm that bloggers' intention to switch their blog services is strongly associated with three factors: satisfaction, sunk costs, and attractive alternatives. Meanwhile, moderating effects are found in gender, but not in sunk costs. Implications for both researchers and practitioners are provided.

Supervisor—Subordinate Guanxi and Employee Work Outcomes: The Mediating Role of Job Satisfaction

Abstract: In this study, we attempt to explain the divergent results found in the relationships between supervisor–subordinate guanxi and employee work outcomes. Specifically, we propose that the relationships between supervisor–subordinate guanxi and participatory management, turnover intentions, and organizational commitment are mediated by job satisfaction. Based on the data collected from a sample of 196 employees of three local manufacturing firms in Zhejiang Province, China, we found that job satisfaction fully mediated the effects of supervisor–subordinate guanxi on participatory management and intentions to leave, but partially mediated the relationship between supervisor–subordinate guanxi and organizational commitment. Theoretical and practical implications are discussed.

Linear Suffix Array Construction by Almost Pure Induced-Sorting

Abstract: We present a linear time and space suffix array (SA) construction algorithm called the SA-IS algorithm.The SA-IS algorithm is novel because of the LMS-substrings used for the problem reduction and the pure induced-sorting (specially coined for this algorithm)used to propagate the order of suffixes as well as that of LMS-substrings, which makes the algorithm almost purely relying on induced sorting at both its crucial steps.The pure induced-sorting renders the algorithm an elegant design and in turn a surprisingly compact implementation which consists of less than 100 lines of C code.The experimental results demonstrate that this newly proposed algorithm yields noticeably better time and space efficiencies than all the currently published linear time algorithms for SA construction.

Stochastic Dominance and Applications to Finance, Risk and Economics

Abstract: Utility in Decision Theory Choice under certainty Basic probability background Choice under uncertainty Utilities and risk attitudes Foundations of Stochastic Dominance Some preliminary mathematics Deriving representations of preferences Stochastic dominance (SD) Issues in Stochastic Dominance A closer look at the mean-variance rule Multivariate SD Stochastic dominance via quantile functions Financial Risk Measures The problem of risk modeling Some popular risk measures Desirable properties of risk measures Choquet Integrals as Risk Measures Extended theory of measures Capacities The Choquet integral Basic properties of the Choquet integral Comonotonicity Notes on copulas A characterization theorem A class of coherent risk measures Consistency with SD Foundational Statistics for Stochastic Dominance From theory to applications Structure of statistical inference Generalities on statistical estimation Nonparametric estimation Basics of hypothesis testing Models and Data in Econometrics Justifications of models Coarse data Modeling dependence structure Some additional statistical tools Applications to Finance Diversification Diversification on convex combinations Prospect and Markowitz SD Market rationality and efficiency SD and rationality of momentum effect Applications to Risk Management Measures of profit/loss for risk analysis REITs and stocks and fixed-income assets Evaluating hedge funds performance Evaluating iShare performance Applications to Economics Indifference curves/location-scale (LS) family LS family for n random seed sources Elasticity of risk aversion and trade Income inequality Appendix: Stochastic Dominance Tests Bibliography Index Exercises appear at the end of each chapter.

Synthesis and Characterization of High-Quality Water-Soluble Near-Infrared-Emitting CdTe/CdS Quantum Dots Capped by N-Acetyl-l-cysteine Via Hydrothermal Method

Abstract: The synthesis of water-soluble near-infrared (NIR)-emitting quantum dots (QDs) in aqueous solution has received much attention recently. However, the stabilizer 3-mercaptopropionic acid, commonly used in the synthesis of NIR-emitting QDs, is notorious for its toxicity and awful odor. Here we chose thiol ligand N-acetyl-l-cysteine (NAC) as the ideal stabilizer and have successfully employed it to synthesize high-quality NIR-emitting CdTe/CdS QDs in a one-step process via a simple hydrothermal route. NAC possesses favorable properties such as nontoxic, nonvolatile, inexpensive, and good water-solubility. Our as-prepared NIR-emitting CdTe/CdS QDs exhibit high photoluminescence quantum yields (45−62%), narrow full-width at half-maximum, and high photostability, thanks to the formation of a protective CdS shell on the CdTe core through the decomposition of NAC in the hydrothermal route under high temperature. The prepared QDs can be applied for bioimaging due to its excellent water-solubility and biological co...

Nitric oxide-induced rapid decrease of abscisic acid concentration is required in breaking seed dormancy in Arabidopsis

Abstract: Nitric oxide (NO) has been reported to be involved in breaking seed dormancy but its mechanism of action is unclear. Here, we report that a rapid accumulation of NO induced an equally rapid decrease of abscisic acid (ABA) that is required for this action in Arabidopsis. Results of quantitative real-time polymerase chain reaction (QRT-PCR) and Western blotting indicate that the NO-induced ABA decrease correlates with the regulation of CYP707A2 transcription and (+)-abscisic acid 8'-hydroxylase (encoded by CYP707A2) protein expression. By analysing cyp707a1, cyp707a2 and cyp707a3 mutants, we found that CYP707A2 plays a major role in ABA catabolism during the first stage of imbibition. Fluorescent images demonstrate that NO is released rapidly in the early hours at the endosperm layer during imbibition. Evidently, such response precedes the enhancement of ABA catabolism which is required for subsequent seed germination.