Showing papers by "The Chinese University of Hong Kong published in 2008"

Hyperglycemia and adverse pregnancy outcomes

Abstract: Background It is controversial whether maternal hyperglycemia less severe than that in diabetes mellitus is associated with increased risks of adverse pregnancy outcomes Methods A total of 25,505 pregnant women at 15 centers in nine countries underwent 75-g oral glucose-tolerance testing at 24 to 32 weeks of gestation Data remained blinded if the fasting plasma glucose level was 105 mg per deciliter (58 mmol per liter) or less and the 2-hour plasma glucose level was 200 mg per deciliter (111 mmol per liter) or less Primary outcomes were birth weight above the 90th percentile for gestational age, primary cesarean delivery, clinically diagnosed neonatal hypoglycemia, and cord-blood serum C-peptide level above the 90th percentile Secondary outcomes were delivery before 37 weeks of gestation, shoulder dystocia or birth injury, need for intensive neonatal care, hyperbilirubinemia, and preeclampsia Results For the 23,316 participants with blinded data, we calculated adjusted odds ratios for adverse pregnancy outcomes associated with an increase in the fasting plasma glucose level of 1 SD (69 mg per deciliter [04 mmol per liter]), an increase in the 1-hour plasma glucose level of 1 SD (309 mg per deciliter [17 mmol per liter]), and an increase in the 2-hour plasma glucose level of 1 SD (235 mg per deciliter [13 mmol per liter]) For birth weight above the 90th percentile, the odds ratios were 138 (95% confidence interval [CI], 132 to 144), 146 (139 to 153), and 138 (132 to 144), respectively; for cord-blood serum C-peptide level above the 90th percentile, 155 (95% CI, 147 to 164), 146 (138 to 154), and 137 (130 to 144); for primary cesarean delivery, 111 (95% CI, 106 to 115), 110 (106 to 115), and 108 (103 to 112); and for neonatal hypoglycemia, 108 (95% CI, 098 to 119), 113 (103 to 126), and 110 (100 to 112) There were no obvious thresholds at which risks increased Significant associations were also observed for secondary outcomes, although these tended to be weaker Conclusions Our results indicate strong, continuous associations of maternal glucose levels below those diagnostic of diabetes with increased birth weight and increased cord-blood serum C-peptide levels

An institution-based view of international business strategy: a focus on emerging economies

Abstract: Leveraging the recent research interest in emerging economies, this Perspective paper argues that an institution-based view of international business (IB) strategy has emerged. It is positioned as one leg that helps sustain the “strategy tripod” (the other two legs consisting of the industry- and resource-based views). We then review four diverse areas of substantive research: (1) antidumping as entry barriers; (2) competing in and out of India; (3) growing the firm in China; and (4) governing the corporation in emerging economies. Overall, we argue that an institution-based view of IB strategy, in combination with industry- and resource-based views, will not only help sustain a strategy tripod, but also shed significant light on the most fundamental questions confronting IB, such as “What drives firm strategy and performance in IB?”

Suicide and Suicidal Behavior

Abstract: Suicidal behavior is a leading cause of injury and death worldwide. Information about the epidemiology of such behavior is important for policy-making and prevention. The authors reviewed government data on suicide and suicidal behavior and conducted a systematic review of studies on the epidemiology of suicide published from 1997 to 2007. The authors' aims were to examine the prevalence of, trends in, and risk and protective factors for suicidal behavior in the United States and cross-nationally. The data revealed significant cross-national variability in the prevalence of suicidal behavior but consistency in age of onset, transition probabilities, and key risk factors. Suicide is more prevalent among men, whereas nonfatal suicidal behaviors are more prevalent among women and persons who are young, are unmarried, or have a psychiatric disorder. Despite an increase in the treatment of suicidal persons over the past decade, incidence rates of suicidal behavior have remained largely unchanged. Most epidemiologic research on suicidal behavior has focused on patterns and correlates of prevalence. The next generation of studies must examine synergistic effects among modifiable risk and protective factors. New studies must incorporate recent advances in survey methods and clinical assessment. Results should be used in ongoing efforts to decrease the significant loss of life caused by suicidal behavior.

Results of the Predictors of Response to CRT (PROSPECT) Trial

Abstract: Background— Data from single-center studies suggest that echocardiographic parameters of mechanical dyssynchrony may improve patient selection for cardiac resynchronization therapy (CRT). In a prospective, multicenter setting, the Predictors of Response to CRT (PROSPECT) study tested the performance of these parameters to predict CRT response. Methods and Results— Fifty-three centers in Europe, Hong Kong, and the United States enrolled 498 patients with standard CRT indications (New York Heart Association class III or IV heart failure, left ventricular ejection fraction ≤35%, QRS ≥130 ms, stable medical regimen). Twelve echocardiographic parameters of dyssynchrony, based on both conventional and tissue Doppler–based methods, were evaluated after site training in acquisition methods and blinded core laboratory analysis. Indicators of positive CRT response were improved clinical composite score and ≥15% reduction in left ventricular end-systolic volume at 6 months. Clinical composite score was improved in 6...

Testing Mediation and Suppression Effects of Latent Variables: Bootstrapping With Structural Equation Models

Abstract: Because of the importance of mediation studies, researchers have been continuously searching for the best statistical test for mediation effect. The approaches that have been most commonly employed include those that use zero-order and partial correlation, hierarchical regression models, and structural equation modeling (SEM). This study extends MacKinnon and colleagues (MacKinnon, Lockwood, Hoffmann, West, & Sheets, 2002; MacKinnon, Lockwood, & Williams, 2004, MacKinnon, Warsi, & Dwyer, 1995) works by conducting a simulation that examines the distribution of mediation and suppression effects of latent variables with SEM, and the properties of confidence intervals developed from eight different methods. Results show that SEM provides unbiased estimates of mediation and suppression effects, and that the bias-corrected bootstrap confidence intervals perform best in testing for mediation and suppression effects. Steps to implement the recommended procedures with Amos are presented.

SoRec: social recommendation using probabilistic matrix factorization

Abstract: Data sparsity, scalability and prediction quality have been recognized as the three most crucial challenges that every collaborative filtering algorithm or recommender system confronts. Many existing approaches to recommender systems can neither handle very large datasets nor easily deal with users who have made very few ratings or even none at all. Moreover, traditional recommender systems assume that all the users are independent and identically distributed; this assumption ignores the social interactions or connections among users. In view of the exponential growth of information generated by online social networks, social network analysis is becoming important for many Web applications. Following the intuition that a person's social network will affect personal behaviors on the Web, this paper proposes a factor analysis approach based on probabilistic matrix factorization to solve the data sparsity and poor prediction accuracy problems by employing both users' social network information and rating records. The complexity analysis indicates that our approach can be applied to very large datasets since it scales linearly with the number of observations, while the experimental results shows that our method performs much better than the state-of-the-art approaches, especially in the circumstance that users have made few or no ratings.

High-quality motion deblurring from a single image

Abstract: We present a new algorithm for removing motion blur from a single image. Our method computes a deblurred image using a unified probabilistic model of both blur kernel estimation and unblurred image restoration. We present an analysis of the causes of common artifacts found in current deblurring methods, and then introduce several novel terms within this probabilistic model that are inspired by our analysis. These terms include a model of the spatial randomness of noise in the blurred image, as well a new local smoothness prior that reduces ringing artifacts by constraining contrast in the unblurred image wherever the blurred image exhibits low contrast. Finally, we describe an effficient optimization scheme that alternates between blur kernel estimation and unblurred image restoration until convergence. As a result of these steps, we are able to produce high quality deblurred results in low computation time. We are even able to produce results of comparable quality to techniques that require additional input images beyond a single blurry photograph, and to methods that require additional hardware.

Corporate governance in emerging economies: A review of the principal-principal perspective: Review paper

Abstract: Instead of traditional principal–agent conflicts espoused in most research dealing with developed economies, principal–principal conflicts have been identified as a major concern of corporate governance in emerging economies. Principal–principal conflicts between controlling shareholders and minority shareholders result from concentrated ownership, extensive family ownership and control, business group structures, and weak legal protection of minority shareholders. Such principal–principal conflicts alter the dynamics of the corporate governance process and, in turn, require remedies different from those that deal with principal–agent conflicts. This article reviews and synthesizes recent research from strategy, finance, and economics on principal–principal conflicts with an emphasis on their institutional antecedents and organizational consequences. The resulting integration provides a foundation upon which future research can continue to build.

Shape- and size-dependent refractive index sensitivity of gold nanoparticles.

Abstract: Gold nanoparticles of different shapes and sizes, including nanospheres, nanocubes, nanobranches, nanorods, and nanobipyramids, were dispersed into water-glycerol mixtures of varying volume ratios to investigate the response of their surface plasmon peaks to the refractive index of the surrounding medium. The refractive index sensitivities and figures of merit were found to be dependent on both the shape and the size of the Au nanoparticles. The index sensitivities generally increase as Au nanoparticles become elongated and their apexes become sharper. Au nanospheres exhibit the smallest refractive index sensitivity of 44 nm/RIU and Au nanobranches exhibit the largest index sensitivity of 703 nm/RIU. Au nanobipyramids possess the largest figures of merit, which increase from 1.7 to 4.5 as the aspect ratio is increased from 1.5 to 4.7.

Noninvasive prenatal diagnosis of fetal chromosomal aneuploidy by massively parallel genomic sequencing of DNA in maternal plasma.

Abstract: Chromosomal aneuploidy is the major reason why couples opt for prenatal diagnosis. Current methods for definitive diagnosis rely on invasive procedures, such as chorionic villus sampling and amniocentesis, and are associated with a risk of fetal miscarriage. Fetal DNA has been found in maternal plasma but exists as a minor fraction among a high background of maternal DNA. Hence, quantitative perturbations caused by an aneuploid chromosome in the fetal genome to the overall representation of sequences from that chromosome in maternal plasma would be small. Even with highly precise single molecule counting methods such as digital PCR, a large number of DNA molecules and hence maternal plasma volume would need to be analyzed to achieve the necessary analytical precision. Here we reasoned that instead of using approaches that target specific gene loci, the use of a locus-independent method would greatly increase the number of target molecules from the aneuploid chromosome that could be analyzed within the same fixed volume of plasma. Hence, we used massively parallel genomic sequencing to quantify maternal plasma DNA sequences for the noninvasive prenatal detection of fetal trisomy 21. Twenty-eight first and second trimester maternal plasma samples were tested. All 14 trisomy 21 fetuses and 14 euploid fetuses were correctly identified. Massively parallel plasma DNA sequencing represents a new approach that is potentially applicable to all pregnancies for the noninvasive prenatal diagnosis of fetal chromosomal aneuploidies.

Dynamic Spectrum Management: Complexity and Duality

Abstract: Consider a communication system whereby multiple users share a common frequency band and must choose their transmit power spectral densities dynamically in response to physical channel conditions. Due to co-channel interference, the achievable data rate of each user depends on not only the power spectral density of its own, but also those of others in the system. Given any channel condition and assuming Gaussian signaling, we consider the problem to jointly determine all users' power spectral densities so as to maximize a system-wide utility function (e.g., weighted sum-rate of all users), subject to individual power constraints. For the discretized version of this nonconvex problem, we characterize its computational complexity by establishing the NP-hardness under various practical settings, and identify subclasses of the problem that are solvable in polynomial time. Moreover, we consider the Lagrangian dual relaxation of this nonconvex problem. Using the Lyapunov theorem in functional analysis, we rigorously prove a result first discovered by Yu and Lui (2006) that there is a zero duality gap for the continuous (Lebesgue integral) formulation. Moreover, we show that the duality gap for the discrete formulation vanishes asymptotically as the size of discretization decreases to zero.

Sarcopenia: Its assessment, etiology, pathogenesis, consequences and future perspectives

Abstract: Sarcopenia is a loss of muscle protein mass and loss of muscle function. It occurs with increasing age, being a major component in the development of frailty. Current knowledge on its assessment, etiology, pathogenesis, consequences and future perspectives are reported in the present review. On-going and future clinical trials on sarcopenia may radically change our preventive and therapeutic approaches of mobility disability in older people.

Entrepreneurship in Emerging Economies: Where Are We Today and Where Should the Research Go in the Future

Abstract: Emerging economies are characterized by an increasing market orientation and an expanding economic foundation. The success of many of these economies is such that they are rapidly becoming major economic forces in the world. Entrepreneurship plays a key role in this economic development. Yet to date, little is known about entrepreneurship in emerging economies. This introductory article to the special issue on entrepreneurship in emerging economies examines the literature that exists to date in this important domain. It then reviews the research that was generated as part of this special issue on this topic. The article concludes with a discussion of the critical future research needs in this area.

Detection and characterization of placental microRNAs in maternal plasma.

Abstract: Background: The discovery of circulating fetal nucleic acids in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. MicroRNAs (miRNAs), a class of small RNAs, have been intensely investigated recently because of their important regulatory role in gene expression. Because nucleic acids of placental origin are released into maternal plasma, we hypothesized that miRNAs produced by the placenta would also be released into maternal plasma. Methods: We systematically searched for placental miRNAs in maternal plasma to identify miRNAs that were at high concentrations in placentas compared with maternal blood cells and then investigated the stability and filterability of this novel class of pregnancy-associated markers in maternal plasma. Results: In a panel of TaqMan MicroRNA Assays available for 157 well-established miRNAs, 17 occurred at concentrations >10-fold higher in the placentas than in maternal blood cells and were undetectable in postdelivery maternal plasma. The 4 most abundant of these placental miRNAs (miR-141, miR-149, miR-299-5p, and miR-135b) were detectable in maternal plasma during pregnancy and showed reduced detection rates in postdelivery plasma. The plasma concentration of miR-141 increased as pregnancy progressed into the third trimester. Compared with mRNA encoded by CSH1 [chorionic somatomammotropin hormone 1 (placental lactogen)], miR-141 was even more stable in maternal plasma, and its concentration did not decrease after filtration. Conclusion: We have demonstrated the existence of placental miRNAs in maternal plasma and provide some information on their stability and physical nature. These findings open up a new class of molecular markers for pregnancy monitoring.

Who suffers more from job insecurity? A Meta-Analytic review

Abstract: The present meta-analysis examined the tenure, age, and gender differences in the relationship between job insecurity and its job-related and health-related consequences. A total of 133 studies, providing 172 independent samples, were included in the analysis. Our results basically replicated Sverke et al.'s (2002) meta-analytic findings with an updated methodological approach and a larger database. The main differences between our findings and Sverke et al.'s are that the negative association between job insecurity and job performance was significant and that the relationship between insecurity and job involvement was smaller in our study. The moderator analysis also indicated that: (1) the positive association between job insecurity and turnover intention was stronger among employees with shorter tenure than those with longer tenure, and was stronger among younger than older employees; (2) the negative effect of insecurity on its health outcomes was more severe among employees with longer tenure than those with shorter tenure, and was more severe among older than younger employees; (3) the relationship between insecurity and the criterion variables was similar across gender. Results are discussed with reference to Hulin's (1991) theory of job adaptation and Greenhalgh and Rosenblatt's (1984) job dependence perspective.

Interpreting TF-IDF term weights as making relevance decisions

Abstract: A novel probabilistic retrieval model is presented It forms a basis to interpret the TF-IDF term weights as making relevance decisions It simulates the local relevance decision-making for every location of a document, and combines all of these “local” relevance decisions as the “document-wide” relevance decision for the document The significance of interpreting TF-IDF in this way is the potential to: (1) establish a unifying perspective about information retrieval as relevance decision-making; and (2) develop advanced TF-IDF-related term weights for future elaborate retrieval models Our novel retrieval model is simplified to a basic ranking formula that directly corresponds to the TF-IDF term weights In general, we show that the term-frequency factor of the ranking formula can be rendered into different term-frequency factors of existing retrieval systems In the basic ranking formula, the remaining quantity - log p(r¯|t ∈ d) is interpreted as the probability of randomly picking a nonrelevant usage (denoted by r¯) of term t Mathematically, we show that this quantity can be approximated by the inverse document-frequency (IDF) Empirically, we show that this quantity is related to IDF, using four reference TREC ad hoc retrieval data collections

Opportunities for green marketing: young consumers

Abstract: – The purpose of this paper is to identify important factors that affect Hong Kong adolescent consumers' green purchasing behaviour., – A total of 6,010 (2,975 males and 3,035 females) adolescents in Hong Kong were recruited through multi‐staged random sampling. They were surveyed on their green purchasing behaviour, environmental attitude, environmental concern, perceived seriousness of environmental problems, perceived environmental responsibility, perceived effectiveness of environmental behaviour, social influence and concern for self‐image in environmental protection., – Multiple regression analysis showed that social influence was the top predictor of Hong Kong adolescents' green purchasing behaviour, followed by environmental concern as the second, concern for self‐image in environmental protection as the third, and perceived environmental responsibility as the fourth top predictor., – A major limitation of this study lies in the self‐reported nature of the survey used. Future study should include some objective assessments (such as observations or other‐reported survey) of the subjects' green purchasing behaviour., – This paper is a useful source of information for international green marketers about what works and what does not in appealing to the young consumers in Hong Kong., – This paper serves as a pioneer study to identify important factors in affecting young consumers' green purchasing behaviour in the Hong Kong context. It offers practical guidelines to international green marketers planning to target the Asian markets.

Screening for gastric cancer in Asia: current evidence and practice

Abstract: Gastric cancer is the second most common cause of death from cancer in Asia. Although surgery is the standard treatment for this disease, early detection and treatment is the only way to reduce mortality. This Review summarises the epidemiology of gastric cancer, and the evidence for, and current practices of, screening in Asia. Few Asian countries have implemented a national screening programme for gastric cancer; most have adopted opportunistic screening of high-risk individuals only. Although screening by endoscopy seems to be the most accurate method for detection of gastric cancer, the availability of endoscopic instruments and expertise for mass screening remains questionable--even in developed countries such as Japan. Therefore, barium studies or serum-pepsinogen testing are sometimes used as the initial screening tool in some countries, and patients with abnormal results are screened by endoscopy. Despite the strong link between infection with Helicobacter pylori and gastric cancer, more data are needed to define the role of its eradication in the prevention of gastric cancer in Asia. At present, there is a paucity of quality data from Asia to lend support for screening for gastric cancer.

Variants in KCNQ1 are associated with susceptibility to type 2 diabetes mellitus.

Abstract: We carried out a multistage genome-wide association study of type 2 diabetes mellitus in Japanese individuals, with a total of 1,612 cases and 1,424 controls and 100,000 SNPs. The most significant association was obtained with SNPs in KCNQ1, and dense mapping within the gene revealed that rs2237892 in intron 15 showed the lowest P value (6.7 x 10(-13), odds ratio (OR) = 1.49). The association of KCNQ1 with type 2 diabetes was replicated in populations of Korean, Chinese and European ancestry as well as in two independent Japanese populations, and meta-analysis with a total of 19,930 individuals (9,569 cases and 10,361 controls) yielded a P value of 1.7 x 10(-42) (OR = 1.40; 95% CI = 1.34-1.47) for rs2237892. Among control subjects, the risk allele of this polymorphism was associated with impairment of insulin secretion according to the homeostasis model assessment of beta-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries.

Challenges, design and analysis of a large-scale p2p-vod system

Abstract: P2P file downloading and streaming have already become very popular Internet applications. These systems dramatically reduce the server loading, and provide a platform for scalable content distribution, as long as there is interest for the content. P2P-based video-on-demand (P2P-VoD) is a new challenge for the P2P technology. Unlike streaming live content, P2P-VoD has less synchrony in the users sharing video content, therefore it is much more difficult to alleviate the server loading and at the same time maintaining the streaming performance. To compensate, a small storage is contributed by every peer, and new mechanisms for coordinating content replication, content discovery, and peer scheduling are carefully designed. In this paper, we describe and discuss the challenges and the architectural design issues of a large-scale P2P-VoD system based on the experiences of a real system deployed by PPLive. The system is also designed and instrumented with monitoring capability to measure both system and component specific performance metrics (for design improvements) as well as user satisfaction. After analyzing a large amount of collected data, we present a number of results on user behavior, various system performance metrics, including user satisfaction, and discuss what we observe based on the system design. The study of a real life system provides valuable insights for the future development of P2P-VoD technology.

Gene silencing in cancer by histone H3 lysine 27 trimethylation independent of promoter DNA methylation

Abstract: Epigenetic silencing in cancer cells is mediated by at least two distinct histone modifications, polycomb-based histone H3 lysine 27 trimethylation (H3K27triM) and H3K9 dimethylation. The relationship between DNA hypermethylation and these histone modifications is not completely understood. Using chromatin immunoprecipitation microarrays (ChIP-chip) in prostate cancer cells compared to normal prostate, we found that up to 5% of promoters (16% CpG islands and 84% non-CpG islands) were enriched with H3K27triM. These genes were silenced specifically in prostate cancer, and those CpG islands affected showed low levels of DNA methylation. Downregulation of the EZH2 histone methyltransferase restored expression of the H3K27triM target genes alone or in synergy with histone deacetylase inhibition, without affecting promoter DNA methylation, and with no effect on the expression of genes silenced by DNA hypermethylation. These data establish EZH2-mediated H3K27triM as a mechanism of tumor-suppressor gene silencing in cancer that is potentially independent of promoter DNA methylation.

Measurement of the specific heat capacity of water-based Al2O3 nanofluid

Abstract: In this letter, we have presented an experimental investigation of the specific heat cp of water-based Al2O3 nanofluid with a differential scanning calorimeter. The result indicates that the specific heat cp of nanofluid decreases gradually as the nanoparticle volume fraction ϕ increases from 0.0% to 21.7%. The relationship between them exhibits good agreement with the prediction from the thermal equilibrium model [Eq. (2)]. The other simple mixing model [Eq. (1)] fails to predict the specific heat cp of nanofluid.