Showing papers by "Hong Kong Baptist University published in 2001"

Effect of abscisic acid on active oxygen species, antioxidative defence system and oxidative damage in leaves of maize seedlings.

Abstract: Leaves of maize (Zea mays L.) seedlings were supplied with different concentrations of abscisic acid (ABA). Its effects on the levels of superoxide radical (O(2)(-)), hydrogen peroxide (H(2)O(2)) and the content of catalytic Fe, the activities of several antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), the contents of several non-enzymatic antioxidants such as ascorbate (ASC), reduced glutathione (GSH), alpha-tocopherol (alpha-TOC) and carotenoid (CAR), and the degrees of the oxidative damage to the membrane lipids and proteins were examined. Treatment with 10 and 100 microM ABA significantly increased the levels of O(2)(-) and H(2)O(2), followed by an increase in activities of SOD, CAT, APX and GR, and the contents of ASC, GSH, alpha-TOC and CAR in a dose- and time-dependent pattern in leaves of maize seedlings. An oxidative damage expressed as lipid peroxidation, protein oxidation, and plasma membrane leakage did not occur except for a slight increase with 100 microM ABA treatment for 24 h. Treatment with 1,000 microM ABA led to a more abundant generation of O(2)(-) and H(2)O(2) and a significant increase in the content of catalytic Fe, which is critical for H(2)O(2)-dependent hydroxyl radical production. The activities of these antioxidative enzymes and the contents of alpha-TOC and CAR were still maintained at a higher level, but no longer further enhanced when compared with the treatment of 100 microM ABA. The contents of ASC and GSH had no changes in leaves treated with 1,000 microM ABA. These results indicate that treatment with low concentrations of ABA (10 to 100 microM) induced an antioxidative defence response against oxidative damage, but a high concentration of ABA (1,000 microM) induced an excessive generation of AOS and led to an oxidative damage in plant cells.

An orthogonal genetic algorithm with quantization for global numerical optimization

Abstract: We design a genetic algorithm called the orthogonal genetic algorithm with quantization for global numerical optimization with continuous variables. Our objective is to apply methods of experimental design to enhance the genetic algorithm, so that the resulting algorithm can be more robust and statistically sound. A quantization technique is proposed to complement an experimental design method called orthogonal design. We apply the resulting methodology to generate an initial population of points that are scattered uniformly over the feasible solution space, so that the algorithm can evenly scan the feasible solution space once to locate good points for further exploration in subsequent iterations. In addition, we apply the quantization technique and orthogonal design to tailor a new crossover operator, such that this crossover operator can generate a small, but representative sample of points as the potential offspring. We execute the proposed algorithm to solve 15 benchmark problems with 30 or 100 dimensions and very large numbers of local minima. The results show that the proposed algorithm can find optimal or close-to-optimal solutions.

Hormonal Changes in the Grains of Rice Subjected to Water Stress during Grain Filling

Abstract: Lodging-resistant rice (Oryza sativa) cultivars usually show slow grain filling when nitrogen is applied in large amounts. This study investigated the possibility that a hormonal change may mediate the effect of water deficit that enhances whole plant senescence and speeds up grain filling. Two rice cultivars showing high lodging resistance and slow grain filling were field grown and applied with either normal or high amount nitrogen (HN) at heading. Well-watered and water-stressed (WS) treatments were imposed 9 days post anthesis to maturity. Results showed that WS increased partitioning of fixed (14)CO(2) into grains, accelerated the grain filling rate but shortened the grain filling period, whereas the HN did the opposite way. Cytokinin (zeatin + zeatin riboside) and indole-3-acetic acid contents in the grains transiently increased at early filling stage and WS treatments hastened their declines at the late grain filling stage. Gibberellins (GAs; GA(1) + GA(4)) in the grains were also high at early grain filling but HN enhanced, whereas WS substantially reduced, its accumulation. Opposite to GAs, abscisic acid (ABA) in the grains was low at early grain filling but WS remarkably enhanced its accumulation. The peak values of ABA were significantly correlated with the maximum grain filling rates (r = 0.92**, P < 0.01) and the partitioning of fixed (14)C into grains (r = 0.95**, P < 0.01). Exogenously applied ABA on pot-grown HN rice showed similar results as those by WS. Results suggest that an altered hormonal balance in rice grains by water stress during grain filling, especially a decrease in GAs and an increase in ABA, enhances the remobilization of prestored carbon to the grains and accelerates the grain filling rate.

New Conjugacy Conditions and Related Nonlinear Conjugate Gradient Methods

Abstract: Conjugate gradient methods are a class of important methods for unconstrained optimization, especially when the dimension is large. This paper proposes a new conjugacy condition, which considers an inexact line search scheme but reduces to the old one if the line search is exact. Based on the new conjugacy condition, two nonlinear conjugate gradient methods are constructed. Convergence analysis for the two methods is provided. Our numerical results show that one of the methods is very efficient for the given test problems.

Water Deficit–Induced Senescence and Its Relationship to the Remobilization of Pre-Stored Carbon in Wheat during Grain Filling

Abstract: Remobilization and transfer of the pre-stored food in vegetative tissues to the grains in monocarpic plants require the initiation of whole plant senescence. However, mechanisms by which plant senescence promotes remobilization of assimilates are rather obscure. This study examined the relationship between the senescence induced by water deficits and C remobilization during grain fill. Two semi-winter wheat cultivars (Triticum aestivum L.),Yangmai 158 and Yangmai 931, were treated with two levels of nitrogen (normal [NN] or high [HN]) and three levels of soil moisture (well-watered, moderate water deficit, and severe water deficit). Results showed that water deficits enhanced the senescence by accelerating loss of leaf nitrogen and chlorophyll and increasing lipid peroxidation. At maturity, 75 to 92% of pre-anthesis C stored in the straw was reallocated to grains in water-deficit treatments, 50 to 80% higher than the amount in well-watered treatments, indicating that water deficits promoted remobilization. The peak values of abscisic acid (ABA) in both leaves and grains under water-defidt treatments were 63 to 144% higher than those under well-watered treatments. The elevated ABA level correlated with the degree of earlier leaf senescence, the 14 C partitioning into grains, and the carbon remobllization. The activites of both add invertase (INV) and sucrose synthase (SS) in grains were also enhanced by water deficits at the midstage of grain fill. Our results suggest that the senescence and remobilization promoted by water defidts during grain fill are coupled processes in wheat, and elevated ABA concentration may play a regulative role.

Array-enhanced coherence resonance: nontrivial effects of heterogeneity and spatial independence of noise.

Abstract: We demonstrate the effect of coherence resonance in a heterogeneous array of coupled Fitz Hugh--Nagumo neurons. It is shown that coupling of such elements leads to a significantly stronger coherence compared to that of a single element. We report nontrivial effects of parameter heterogeneity and spatial independence of noise on array-enhanced coherence resonance; especially, we find that (i) the coherence increases as spatial correlation of the noise decreases, and (ii) inhomogeneity in the parameters of the array enhances the coherence. Our results have the implication that generic heterogeneity and background noise can play a constructive role to enhance the time precision of firing in neural systems.

SOR-like Methods for Augmented Systems

Abstract: Several SOR-like methods are proposed for solving augmented systems. These have many different applications in scientific computing, for example, constrained optimization and the finite element method for solving the Stokes equation. The convergence and the choice of optimal parameter for these algorithms are studied. The convergence and divergence regions for some algorithms are given, and the new algorithms are applied to solve the Stokes equations as well.

Does Culture Affect Behavior and Performance of Firms? The Case of Joint Ventures in China

Abstract: This study applies a resource-based view of the firm to analyze data from a sample of 898 joint-venture firms in China, including both joint ventures established by overseas Chinese and by firms from Western cultures. It is hypothesized that culture could influence the timing of entry of joint ventures, their investment preferences, and performance. ANOVAs and regressions were conducted, and the results suggest the impact of cultural as well as technological resources. This paper concludes with a discussion on the implications of the findings.

A measure of retail service quality

Abstract: Current measures of service quality for retail stores are scarce. A validated Retail Service Quality Scale is used to study the service quality delivery of a department store chain and its impact on consumption behaviour. It results in six dimensions; they are namely: personal interaction; policy; physical appearance; promises; problem solving; and convenience. The findings show that the impact of physical appearance and the policy are salient on the overall perceived service quality and the future shopping behaviour respectively. Among the six service dimensions, the physical appearance and policy have the greatest impact on the overall service quality and on future consumption respectively. The implications for practitioners and researchers are discussed.

An Investigation of Decision‐Making Styles of Consumers in China

Abstract: This study investigates Chinese consumers' decision-making styles. The Consumer Style Inventory (CSI) is administered to 387 adult consumers in China. Both an exploratory factor analysis and a confirmatory factor analysis are adopted to validate the CSI inventory. This results in an eighteen-item and seven-factor solution. Findings indicate that five decision-making styles are valid and reliable in Chinese culture: perfectionistic, novelty-fashion conscious, recreational, price conscious, and confused by overchoice. Cluster analysis is employed to identify prominent market segments. Based on the findings, three segments are formed: trendy and perfectionistic consumer, traditional and pragmatic consumer, as well as confused by overchoice consumer. Marketing and management implications are discussed.

Workplace justice, citizenship behavior, and turnover intentions in a union context: examining the mediating role of perceived union support and union instrumentality.

Abstract: This study examined the relationship between workplace justice afforded by the grievance system and the union outcomes of citizenship behavior and turnover intentions and the mechanisms that underpin these relationships. Respondents (N = 187) were members of a large public sector union in Singapore. Results revealed that perceived union support and union instrumentality fully mediated the relationship between the dimensions of workplace justice and citizenship behavior directed toward the union (OCBO) and citizenship behavior directed at other union members (OCBI). Union instrumentality partially mediated the procedural justice–turnover intentions relationship.

Grain sink strength may be related to the poor grain filling of indica-japonica rice (Oryza sativa) hybrids.

Abstract: The physiological and biochemical factors contributing to poor grain filling of indica-japonica rice (Oryza sativa L.) hybrids were studied by analyzing the role of grain sink strength in dry matter accumulation of grains of two types of rice cultivars, Yayou 2 (an indica-japonica hybrid) and Yanjing 2 (a japonica cultivar). Carbon dioxide enrichment and plant hormone application were imposed at anthesis and the number of endosperm cells, dry matter accumulation and the activities of some sugar-metabolizing enzymes of grains were measured during grain filling. In Yayou 2, strong-potential grains (SPGs) accumulated dry weight much earlier than weak-potential grains (WPGs), but this difference was not obvious for Yanjing 2. Carbon dioxide enrichment imposed after heading significantly stimulated dry matter accumulation of WPGs of Yayou 2, but had little influence on WPGs of Yanjing 2 and SPGs of both cultivars. Leaf sheath dry matter decreased steadily in both cultivars during early stages of grain filling and accumulated during the later stages. Carbon dioxide enrichment increased leaf sheath dry matter. Dry matter accumulated by grains was linearly related to the increases in endosperm cell numbers and the activities of sucrose synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) in SPGs and WPGs of both cultivars. Application of either 6-benzyladenine or abscisic acid had no significant influences on both endosperm cell number and grain dry matter accumulation. These results suggest that grain sink strength, determined by both cell numbers, SS and AGPase activities in the endosperm control the dry matter accumulation of grains.

Effect of dissolved organic matter from sludge and sludge compost on soil copper sorption.

Abstract: Interaction of Cu with dissolved organic matter (DOM) is an important physicochemical process affecting Cu mobility in soils. The aim of this study was to investigate the effects of DOM from anaerobically digested dewatered sludge and sludge compost on the sorption of Cu on an acidic sandy loam and a calcareous clay loam. In the presence of DOM, Cu sorption capacity decreased markedly for both soils, especially for the calcareous soil. The Cu sorption isotherms could be well described by the Freundlich equation (r 2 = 0.99), and the binding intensity parameter of soils in the presence of sludge DOM was lower than compost DOM. An increase in DOM concentration significantly reduced the sorption of Cu by both soils. Within the Cu and DOM concentration range studied, the decrease in Cu sorption caused by sludge DOM was consistently greater than that of compost DOM. This might be attributed to the greater amount of hydrophobic fraction of DOM in the compost. Moreover, the reduction of Cu sorption caused by DOM was more obvious in the soil with higher pH. In addition, the sorption of Cu increased with an increase in pH for both soils without the addition of DOM, while Cu sorption in the presence of DOM was unexpectedly decreased with an increase in pH at a pH >6.8. This implied that DOM produced by sludge or other C-enriched organic wastes heavily applied on calcareous soils might facilitate the leaching loss of Cu because of the formation of soluble DOM-metal complexes.

Students' Attitudes to Classroom English Learning: A Cross-Cultural Study.

Abstract: In recent years researchers have developed a range of perspectives for conceptualizing the influences of culture on thinking and behaving. Three perspectives which are of special potential relevance to language teaching are the following: the distinction between collectivism and individualism; different perceptions of power and authority; and different types of achievement motivation. These dimensions were taken as the basis for a survey of students’ attitudes towards classroom English learning in eight East Asian countries and three European countries. It was found that most students in all countries question the traditional authority-based, transmission mode of learning. They wish to participate actively in exploring knowledge and have positive attitudes towards working purposefully, in groups, towards common goals. Whilst there were statistically significant differences between the mean responses of Asian and European students on several items, the numerical differences were not great and the overall patterns of responses were strikingly similar. Furthermore, within Asia and within Europe, there were significant differences between individual countries, and in every country there was a wide range of individual differences. Whilst these ‘deep-structure’ cross-cultural similarities may hide important ‘surface-structure’ differences in how students like to learn, they also serve to make us question some commonly held assumptions about the attitudes of Asian and Western students.

A note on generalized aberration in factorial designs

Abstract: In this paper we extend the wordlength pattern and minimum aberration for non-regular factorials The new concepts, the generalized wordlength pattern and minimum generalized aberration, are proposed Some connections between the generalized wordlength pattern and uniformity are given Some applications of the new concepts in the Blackett and Burman's designs are discussed

Realism and constructivism in strategy research: a critical realist response to Mir and Watson

Abstract: Mir and Watson (2000) advocate that constructivism has the potential to inform strategy research. In their discussions, they compare constructivism with realism, and highlight certain alleged strengths of the former over the latter. Although their paper provides some insights, their version of constructivism is problematic and their understanding of realism is inaccurate. In this note we clarify some key issues concerning constructivism and realism. Moreover, we argue that Mir and Watson's insights can be accommodated within a critical realist framework. Copyright © 2001 John Wiley & Sons, Ltd.

Productivity Losses Associated With Diabetes in the U.S.

Abstract: OBJECTIVE — The objective of this study was to estimate the cost of productivity losses in the U.S. attributable to diabetes, with regard to specific demographic and disease-related characteristics in the U.S. RESEARCH DESIGN AND METHODS — We used the 1989 National Health Interview Survey, a random survey of individuals in the U.S. that included a diabetes supplement. Data on individuals were obtained for labor force participation, hours of work, demographic and occupational characteristics, self-reported health status, and several variables that indicated the presence, duration, and severity (complications) of diabetes. Using multivariate regression analyses, we estimated the association of independent variables (e.g., demographics, health, and diabetes status) with labor force participation, hours of work lost, and the economic value of lost work attributable to diabetes and its complications and duration. RESULTS — In general, the presence of diabetes and complications were found to be related to workforce participation variables. The magnitude of the lost-productivity costs depended on personal characteristics and on the presence and status of diabetes. In general, the loss of yearly earnings amounted to about a one-third reduction in earnings and ranged from $3,700 to $8,700 per annum. CONCLUSIONS — Diabetes has a considerable net effect on earnings, and the complications and duration of diabetes have compound effects. Our findings have implications for the cost-effectiveness of diabetes control; the presence of complicating factors is the single most important predictive factor in lost productivity costs attributable to diabetes, and thus the avoidance or retardation of complications will have an impact on indirect health-related costs.

Fast fractal image encoding based on adaptive search

Abstract: This paper presents a new adaptive search approach to reduce the computational complexity of fractal encoding. A simple but very efficient adaptive necessary condition is introduced to exclude a large number of unqualified domain blocks so as to speed-up fractal image compression. Furthermore, we analyzed an unconventional affine parameter that has better properties than the conventional luminance offset. Specifically, we formulated an optimal bit allocation scheme for the simultaneous quantizations of the usual scaling and the aforementioned unconventional affine parameter. Experiments on standard images showed that our adaptive search method yields superior performance over conventional fractal encoding.