Showing papers by "Hong Kong Baptist University published in 2011"

Interventions for preventing obesity in children

Abstract: The current evidence suggests that many diet and exercise interventions to prevent obesity in children are not effective in preventing weight gain, but can be effective in promoting a healthy diet and increased physical activity levels.Being very overweight (obese) can cause health, psychological and social problems for children. Children who are obese are more likely to have weight and health problems as adults. Programmes designed to prevent obesity focus on modifying one or more of the factors considered to promote obesity.This review included 22 studies that tested a variety of intervention programmes, which involved increased physical activity and dietary changes, singly or in combination. Participants were under 18 and living in Asia, South America, Europe or North America. There is not enough evidence from trials to prove that any one particular programme can prevent obesity in children, although comprehensive strategies to address dietary and physical activity change, together with psycho-social support and environmental change may help. There was a trend for newer interventions to involve their respective communities and to include evaluations.Future research might usefully assess changes made on behalf of entire populations, such as improvements in the types of foods available at schools and in the availability of safe places to run and play, and should assess health effects and costs over several years.The programmes in this review used different strategies to prevent obesity so direct comparisons were difficult. Also, the duration of the studies ranged from 12 weeks to three years, but most lasted less than a year.

Simultaneous Enhancement of Open-Circuit Voltage, Short-Circuit Current Density, and Fill Factor in Polymer Solar Cells

Abstract: Simultaneous enhancement of open-circuit voltage, short-circuit current density, and fill factor in highly efficient polymer solar cells by incorporating an alcohol/water-soluble conjugated polymer as cathode interlayer is domonstrated. When combined with a low-bandgap polymer PTB7 as the electron donor material, the power efficiency of the devices is improved to a certified 8.370%. Due to the drastic improvement in efficiency and easy utilization, this method opens new opportunities for PSCs from various material systems to improve towards 10% efficiency.

A user-centric evaluation framework for recommender systems

Abstract: This research was motivated by our interest in understanding the criteria for measuring the success of a recommender system from users' point view. Even though existing work has suggested a wide range of criteria, the consistency and validity of the combined criteria have not been tested. In this paper, we describe a unifying evaluation framework, called ResQue (Recommender systems' Quality of user experience), which aimed at measuring the qualities of the recommended items, the system's usability, usefulness, interface and interaction qualities, users' satisfaction with the systems, and the influence of these qualities on users' behavioral intentions, including their intention to purchase the products recommended to them and return to the system. We also show the results of applying psychometric methods to validate the combined criteria using data collected from a large user survey. The outcomes of the validation are able to 1) support the consistency, validity and reliability of the selected criteria; and 2) explain the quality of user experience and the key determinants motivating users to adopt the recommender technology. The final model consists of thirty two questions and fifteen constructs, defining the essential qualities of an effective and satisfying recommender system, as well as providing practitioners and scholars with a cost-effective way to evaluate the success of a recommender system and identify important areas in which to invest development resources.

Efficient Reversible Watermarking Based on Adaptive Prediction-Error Expansion and Pixel Selection

Abstract: Prediction-error expansion (PEE) is an important technique of reversible watermarking which can embed large payloads into digital images with low distortion. In this paper, the PEE technique is further investigated and an efficient reversible watermarking scheme is proposed, by incorporating in PEE two new strategies, namely, adaptive embedding and pixel selection. Unlike conventional PEE which embeds data uniformly, we propose to adaptively embed 1 or 2 bits into expandable pixel according to the local complexity. This avoids expanding pixels with large prediction-errors, and thus, it reduces embedding impact by decreasing the maximum modification to pixel values. Meanwhile, adaptive PEE allows very large payload in a single embedding pass, and it improves the capacity limit of conventional PEE. We also propose to select pixels of smooth area for data embedding and leave rough pixels unchanged. In this way, compared with conventional PEE, a more sharply distributed prediction-error histogram is obtained and a better visual quality of watermarked image is observed. With these improvements, our method outperforms conventional PEE. Its superiority over other state-of-the-art methods is also demonstrated experimentally.

Sequential Establishment of Stripe Patterns in an Expanding Cell Population

Abstract: Periodic stripe patterns are ubiquitous in living organisms, yet the underlying developmental processes are complex and difficult to disentangle. We describe a synthetic genetic circuit that couples cell density and motility. This system enabled programmed Escherichia coli cells to form periodic stripes of high and low cell densities sequentially and autonomously. Theoretical and experimental analyses reveal that the spatial structure arises from a recurrent aggregation process at the front of the continuously expanding cell population. The number of stripes formed could be tuned by modulating the basal expression of a single gene. The results establish motility control as a simple route to establishing recurrent structures without requiring an extrinsic pacemaker.

Model-Free Feature Screening for Ultrahigh-Dimensional Data

Abstract: With the recent explosion of scientific data of unprecedented size and complexity, feature ranking and screening are playing an increasingly important role in many scientific studies. In this article, we propose a novel feature screening procedure under a unified model framework, which covers a wide variety of commonly used parametric and semiparametric models. The new method does not require imposing a specific model structure on regression functions, and thus is particularly appealing to ultrahigh-dimensional regressions, where there are a huge number of candidate predictors but little information about the actual model forms. We demonstrate that, with the number of predictors growing at an exponential rate of the sample size, the proposed procedure possesses consistency in ranking, which is both useful in its own right and can lead to consistency in selection. The new procedure is computationally efficient and simple, and exhibits a competent empirical performance in our intensive simulations and real ...

New Design Tactics in OLEDs Using Functionalized 2‐Phenylpyridine‐Type Cyclometalates of Iridium(III) and Platinum(II)

Abstract: As a result of their outstanding attributes, organic light-emitting diodes (OLEDs) and white organic light-emitting diodes (WOLEDs) have been recognized in recent years as the most promising candidates for future flat-panel display technologies and next generation solid-state energy-saving lighting sources New advancements in the area of high performance triplet emitters become vital for realizing more practical applications In this regard, several critical issues must be carefully identified and addressed, and these include the ways to enhance device efficiency and suppress efficiency roll-off, to achieve versatile color tuning and simple device manufacture, as well as to obtain high-quality white light from WOLEDs It has been shown that some functionalized phosphorescent Ir(III) and Pt(II) ppy-type cyclometalated complexes (ppy = 2-phenylpyridine) possess unique features that are suitable for solving these difficult and challenging tasks In this Focus Review, we will highlight the recent design tactics adopted for these functional metallophosphors and the critical roles they may play in developing more realistic devices

Highly enantioselective hydrogenation of quinolines using phosphine-free chiral cationic ruthenium catalysts: scope, mechanism, and origin of enantioselectivity.

Abstract: Asymmetric hydrogenation of quinolines catalyzed by chiral cationic η6-arene–N-tosylethylenediamine–Ru(II) complexes have been investigated. A wide range of quinoline derivatives, including 2-alkylquinolines, 2-arylquinolines, and 2-functionalized and 2,3-disubstituted quinoline derivatives, were efficiently hydrogenated to give 1,2,3,4-tetrahydroquinolines with up to >99% ee and full conversions. This catalytic protocol is applicable to the gram-scale synthesis of some biologically active tetrahydroquinolines, such as (−)-angustureine, and 6-fluoro-2-methyl-1,2,3,4-tetrahydroquinoline, a key intermediate for the preparation of the antibacterial agent (S)-flumequine. The catalytic pathway of this reaction has been investigated in detail using a combination of stoichiometric reaction, intermediate characterization, and isotope labeling patterns. The evidence obtained from these experiments revealed that quinoline is reduced via an ionic and cascade reaction pathway, including 1,4-hydride addition, isomeriz...

Organometallic acetylides of PtII, AuI and HgII as new generation optical power limiting materials

Abstract: Within the scope of nonlinear optics, optical power limiting (OPL) materials are commonly regarded as an important class of compounds which can protect the delicate optical sensors or human eyes from sudden exposure to damaging intense laser beams. Recent efforts have been devoted to developing organometallic acetylide complexes, dendrimers and polymers as high performance OPL materials of the next generation which can favorably optimize the optical limiting/transparency trade-off issue. These metallated materials offer a new avenue towards a new family of highly transparent homo- and heterometallic optical limiters with good solution processability which outperform those of current state-of-the-art visible-light-absorbing competitors such as fullerenes, metalloporphyrins and metallophthalocyanines. This critical review aims to provide a detailed account on the recent advances of these novel OPL chromophores. Their OPL activity was shown to depend strongly on the electronic characters of the aryleneethynylene ligand and transition metal moieties as well as the conjugation chain length of the compounds. Strategies including copolymerization with other transition metals, change of structural geometry, use of a dendritic platform and variation of the type and content of transition metal ions would strongly govern their photophysical behavior and improve the resulting OPL responses. Special emphasis is placed on the structure–OPL response relationships of these organometallic acetylide materials. The research endeavors for realizing practical OPL devices based on these materials have also been presented. This article concludes with perspectives on the current status of the field, as well as opportunities that lie just beyond its frontier (106 references).

Internal Control Weakness and Bank Loan Contracting: Evidence from SOX Section 404 Disclosures

Abstract: Using a sample of borrowing firms who filed SOX Section 404 disclosures first-time with the SEC, this study compares various features of loan contracts between firms with internal control weakness (ICW) problems and those without such problems. Our results show the following. First, the loan spread is higher for ICW firms than for non-ICW firms by about 37 basis points in the full-model regression, after controlling for all other factors that are known to influence loan contract terms. Second, firms with more severe, company-level ICW problems pay significantly higher loan rates, compared with those with less severe, account-level ICW problems. Third, lenders impose tighter nonprice terms on firms with ICW problems than they do on those without such problems. Fourth, fewer (more) lenders are attracted to loan contracts involving firms with (without) ICW problems. Finally, we also provide evidence that lenders charge a higher loan rate, are more likely to require collateral, and structure their loans with fewer participant lenders in a loan syndicate for borrowers who failed to remediate previously disclosed ICW problems, but there is no indication that lenders penalize those who remediated the problem. Our results shed light on the empirical validity of the alleged benefits associated with Section 404 disclosures from the debt market perspective.

Materialism and conspicuous consumption in China: a cross-cultural examination

Abstract: With the growing rise in consumer spending and economic power in Asian societies, it is increasingly important to explore the implications of these developments on consumer culture. This cross-cultural study first discusses the rise of materialism and conspicuous consumption in post-revolution China then examines differences in these phenomena between young adult consumers, aged 18–35, living in urban China and the United States. Utilizing survey data from over 600 respondents, significant differences were found in both materialism and conspicuous consumption, with Chinese young adults scoring higher in both variables. The findings show, that compared with past comparative studies, it appears both materialism and conspicuous consumption are on the rise among urban Chinese consumers.

Processing private queries over untrusted data cloud through privacy homomorphism

Abstract: Query processing that preserves both the data privacy of the owner and the query privacy of the client is a new research problem. It shows increasing importance as cloud computing drives more businesses to outsource their data and querying services. However, most existing studies, including those on data outsourcing, address the data privacy and query privacy separately and cannot be applied to this problem. In this paper, we propose a holistic and efficient solution that comprises a secure traversal framework and an encryption scheme based on privacy homomorphism. The framework is scalable to large datasets by leveraging an index-based approach. Based on this framework, we devise secure protocols for processing typical queries such as k-nearest-neighbor queries (kNN) on R-tree index. Moreover, several optimization techniques are presented to improve the efficiency of the query processing protocols. Our solution is verified by both theoretical analysis and performance study.

A Systematic Review of Information and Communication Technology–Based Interventions for Promoting Physical Activity Behavior Change in Children and Adolescents

Abstract: Background: A growing body of research has employed information and communication technologies (ICTs) such as the Internet and mobile phones for disseminating physical activity (PA) interventions with young populations. Although several systematic reviews have documented the effects of ICT-based interventions on PA behavior, very few have focused on children and adolescents specifically. Objectives: The present review aimed to systematically evaluate the efficacy and methodological quality of ICT-based PA interventions for children and adolescents based on evidence from randomized controlled trials. Methods: Electronic databases Medline, PsycInfo, CINAHL, and Web of Science were searched to retrieve English language articles published in international academic peer-reviewed journals from January 1, 1997, through December 31, 2009. Included were articles that provided descriptions of interventions designed to improve PA-related cognitive, psychosocial, and behavioral outcomes and that used randomized controlled trial design, included only children (6-12 years old) and adolescents (13-18 years old) in both intervention and control groups, and employed Internet, email, and/or short message services (SMS, also known as text messaging) as one or more major or assistive modes to deliver the intervention. Results: In total, 9 studies were analyzed in the present review. All studies were published after 2000 and conducted in Western countries. Of the 9 studies, 7 demonstrated positive and significant within-group differences in at least one psychosocial or behavioral PA outcome. In all, 3 studies reported positive and significant between-group differences favoring the ICT group. When between-group differences were compared across studies, effect sizes were small in 6 studies and large in 3 studies. With respect to methodological quality, 7 of the 9 studies had good methodological quality. Failure to report allocation concealment, blinding to outcome assessment, and lack of long-term follow-up were the criteria met by the fewest studies. In addition, 5 studies measured the intervention exposure rate and only 1 study employed objective measures to record data. Conclusion: The present review provides evidence supporting the positive effects of ICTs in PA interventions for children and adolescents, especially when used with other delivery approaches (ie, face-to-face). Because ICT delivery approaches are often mixed with other approaches and these studies sometimes lack a comparable control group, additional research is needed to establish the true independent effects of ICT as an intervention delivery mode. Although two-thirds of the studies demonstrated satisfactory methodological quality, several quality criteria should be considered in future studies: clear descriptions of allocation concealment and blinding of outcome assessment, extension of intervention duration, and employment of objective measures in intervention exposure rate. Due to the small number of studies that met inclusion criteria and the lack of consistent evidence, researchers should be cautious when interpreting the findings of the present review. [J Med Internet Res 2011;13(3):e48]

Regioregular Pyridal[2,1,3]thiadiazole π-Conjugated Copolymers

Abstract: π-Conjugated, narrow band gap copolymers containing pyridal[2,1,3]thiadiazole (PT) were synthesized via starting materials that prevent random incorporation of the PT heterocycles relative to the backbone vector. Two regioregular structures could be obtained: in one the PTs are oriented in the same direction, and in the other the orientation of the PTs alternates every other repeat unit. Compared to their regiorandom counterparts, the regioregular polymers exhibit a 2 orders of magnitude increase of the hole mobilites, from 0.005 to 0.6 cm2 V–1 s–1, as determined by field-effect transistor measurements.

Product-related deception in e-commerce: a theoretical perspective

Abstract: With the advent of e-commerce, the potential of new Internet technologies to mislead or deceive consumers has increased considerably This paper extends prior classifications of deception and presents a typology of product-related deceptive information practices that illustrates the various ways in which online merchants can deceive consumers via e-commerce product websites The typology can be readily used as educational material to promote consumer awareness of deception in e-commerce and as input to establish benchmarks for good business practices for online companies In addition, the paper develops an integrative model and a set of theory-based propositions addressing why consumers are deceived by the various types of deceptive information practices and what factors contribute to consumer success (or failure) in detecting such deceptions The model not only enhances our conceptual understanding of the phenomenon of product-based deception and its outcomes in e-commerce but also serves as a foundation for further theoretical and empirical investigations Moreover, a better understanding of the factors contributing to or inhibiting deception detection can also help government agencies and consumer organizations design more effective solutions to fight online deception

Achieving Brand Loyalty Through Sponsorship: The Role of Fit and Self-Congruity

Abstract: Managers increasingly seek to develop brand loyalty through sponsorship activities, though this relationship has not been solidly established. This article models and demonstrates the impact of sponsorship on brand loyalty. The studied concepts and relationships emerge from both the sponsorship and consumer-brand relationship literature. The experimental design relies on before-and-after measurements and multiple exposures to the sponsorship. Thus this study demonstrates that sponsorship exposure has a positive impact on brand affect, brand trust, and brand loyalty. The change in brand loyalty from before to after sponsorship exposure reflects two persuasion processes. First, self-congruity with an event enhances brand loyalty through event and brand affect. Second, perceived fit between the event and the brand has a positive effect on brand affect, through attitude toward the sponsorship, and on brand trust, such that it ultimately influences brand loyalty. Brand affect is identified as an important mediator of sponsorship effects.

Feature Selection and Kernel Learning for Local Learning-Based Clustering

Abstract: The performance of the most clustering algorithms highly relies on the representation of data in the input space or the Hilbert space of kernel methods. This paper is to obtain an appropriate data representation through feature selection or kernel learning within the framework of the Local Learning-Based Clustering (LLC) (Wu and Scholkopf 2006) method, which can outperform the global learning-based ones when dealing with the high-dimensional data lying on manifold. Specifically, we associate a weight to each feature or kernel and incorporate it into the built-in regularization of the LLC algorithm to take into account the relevance of each feature or kernel for the clustering. Accordingly, the weights are estimated iteratively in the clustering process. We show that the resulting weighted regularization with an additional constraint on the weights is equivalent to a known sparse-promoting penalty. Hence, the weights of those irrelevant features or kernels can be shrunk toward zero. Extensive experiments show the efficacy of the proposed methods on the benchmark data sets.

Does Self-Compassion Mitigate the Association Between Childhood Maltreatment and Later Emotion Regulation Difficulties? A Preliminary Investigation

Abstract: Child maltreatment-related outcomes range from no symptom expression to suicide. Increasingly, the diverse presentations have been conceptualized as core system dysregulation, including emotion dysregulation. Self-compassion has been advanced as a self-regulation strategy for countering negative self-directed emotions. This study explored whether individual differences in self-compassion would play a role in loosening the associations among childhood maltreatment severity and later emotion regulation difficulties. The sample consisted of transition-age youth (N = 81) seeking treatment for problem substance use. Self-compassion was negatively associated with emotion regulation difficulties and childhood maltreatment, and predicted emotion dysregulation above and beyond maltreatment history, current severity of psychological distress, and problem substance use. In addition, self-compassion mediated the relationship between childhood maltreatment severity and later emotion dysregulation. These findings provide an impetus for further research into the relevance of self-compassion for maltreatment-related impairment.

Simultaneous optimization of charge-carrier balance and luminous efficacy in highly efficient white polymer light-emitting devices.

Abstract: The use of white organic light-emitting devices (WOLEDs) for solid-state lighting applications is becoming increasingly attractive, [ 1 − 5 ] given that legislation in more countries is banning the use of ineffi cient incandescent lamps. Moreover, since fl uorescent lamps involve the use of mercury and its disposal represents a great challenge, many scientists have been working aggressively to make the replacement of the fl uorescent light sources by WOLEDs a reality. Indeed, the effi ciency of multilayer vacuum-evaporated WOLEDs based on small molecules has been greatly improved in the past several years [ 6 − 10 ] and has already exceeded that of fl uorescent lamps. [ 11 ] In contrast, despite many unique advantages, such as low-cost manufacturing using solution-processing techniques, easy processability over large-areas by spin-coating or ink-jet printing, compatibility with fl exible substrates, a relatively small amount of wasted material, and precise control of the doping level, the application of white polymer light-emitting diodes (WPLEDs) is still severely hindered by the relatively low device effi ciency. [ 3 , 12 − 16 ]

Bipolar anthracene derivatives containing hole- and electron-transporting moieties for highly efficient blue electroluminescence devices

Abstract: A series of bipolar anthracene derivatives containing hole-transporting triphenylamine and electron-transporting benzimidazole moieties were synthesized and characterized. These compounds possess high thermal properties and quantum yield in toluene solution but their photoluminescence spectra are sensitive to the polarity of the solvent. Three types of devices were fabricated to investigate their electron-transporting and hole-transporting as well as light-emitting properties. The electroluminescence spectra for the three derivatives B1, B3 and B4 show that they emit blue light, while the B2-based devices produced white light at a low current density because of the electromer formation. Moreover, a single layer OLED device for B4 exhibited a current efficiency of 3.33 cd A−1 with a pure blue color of CIE(x,y) of (0.16, 0.16) at 20 mA cm−2 and a maximum brightness of 8472 cd m−2 at 8.7 V.