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Showing papers by "Hong Kong Baptist University published in 2012"


Journal ArticleDOI
01 Dec 2012
TL;DR: This study conducted a systematic review of eWOM research and identified key factors related to the major elements of the social communication literature and built an integrative framework explaining the impact of e WOM communication on consumer behavior.
Abstract: The notion of electronic word-of-mouth (eWOM) communication has received considerable attention in both business and academic communities. Numerous studies have been conducted to examine the effectiveness of eWOM communication. The scope of published studies on the impact of eWOM communication is large and fragmented and little effort has been made to integrate the findings of prior studies and evaluate the status of the research in this area. In this study, we conducted a systematic review of eWOM research. Building upon our literature analysis, we used the social communication framework to summarize and classify prior eWOM studies. We further identified key factors related to the major elements of the social communication literature and built an integrative framework explaining the impact of eWOM communication on consumer behavior. We believe that the framework will provide an important foundation for future eWOM research work.

1,132 citations


Journal ArticleDOI
TL;DR: A counter-intuitive dual-polarity flat lens based on helicity-dependent phase discontinuities for circularly polarized light is experimentally demonstrated by controlling the helicity of the input light, and the positive and negative polarity are interchangeable in one identical flat lens.
Abstract: Surface topography and refractive index profile dictate the deterministic functionality of a lens. The polarity of most lenses reported so far, that is, either positive (convex) or negative (concave), depends on the curvatures of the interfaces. Here we experimentally demonstrate a counter-intuitive dual-polarity flat lens based on helicity-dependent phase discontinuities for circularly polarized light. Specifically, by controlling the helicity of the input light, the positive and negative polarity are interchangeable in one identical flat lens. Helicity-controllable real and virtual focal planes, as well as magnified and demagnified imaging, are observed on the same plasmonic lens at visible and near-infrared wavelengths. The plasmonic metalens with dual polarity may empower advanced research and applications in helicity-dependent focusing and imaging devices, angular-momentum-based quantum information processing and integrated nano-optoelectronics.

975 citations


Journal ArticleDOI
TL;DR: Due to potential human health risks from long-term exposure to BPA, body burden of the contaminant should be monitored.

882 citations


Journal ArticleDOI
TL;DR: This work investigates the interaction of circularly polarized (CP) light at an interface composed of a dipole antenna array to create spatially varying abrupt phase discontinuities and designs and experimentally demonstrates an ultrathin phase gradient interface to generate a broadband optical vortex beam based on the above principle.
Abstract: Ultrathin metasurfaces consisting of a monolayer of subwavelength plasmonic resonators are capable of generating local abrupt phase changes and can be used for controlling the wavefront of electromagnetic waves. The phase change occurs for transmitted or reflected wave components whose polarization is orthogonal to that of a linearly polarized (LP) incident wave. As the phase shift relies on the resonant features of the plasmonic structures, it is in general wavelength-dependent. Here, we investigate the interaction of circularly polarized (CP) light at an interface composed of a dipole antenna array to create spatially varying abrupt phase discontinuities. The phase discontinuity is dispersionless, that is, it solely depends on the orientation of dipole antennas, but not their spectral response and the wavelength of incident light. By arranging the antennas in an array with a constant phase gradient along the interface, the phenomenon of broadband anomalous refraction is observed ranging from visible to ...

841 citations


Journal ArticleDOI
TL;DR: This optimised polymer semiconductor represents a significant progress in semiconductor development, dispelling prevalent skepticism surrounding practical usability of organic semiconductors for high-performance microelectronic devices, opening up application opportunities hitherto functionally or economically inaccessible with silicon technologies, and providing an excellent structural framework for fundamental studies of charge transport in organic systems.
Abstract: Microelectronic circuits/arrays produced via high-speed printing instead of traditional photolithographic processes offer an appealing approach to creating the long-sought after, low-cost, large-area flexible electronics. Foremost among critical enablers to propel this paradigm shift in manufacturing is a stable, solution-processable, high-performance semiconductor for printing functionally capable thin-film transistors — fundamental building blocks of microelectronics. We report herein the processing and optimisation of solution-processable polymer semiconductors for thin-film transistors, demonstrating very high field-effect mobility, high on/off ratio, and excellent shelf-life and operating stabilities under ambient conditions. Exceptionally high-gain inverters and functional ring oscillator devices on flexible substrates have been demonstrated. This optimised polymer semiconductor represents a significant progress in semiconductor development, dispelling prevalent skepticism surrounding practical usability of organic semiconductors for high-performance microelectronic devices, opening up application opportunities hitherto functionally or economically inaccessible with silicon technologies, and providing an excellent structural framework for fundamental studies of charge transport in organic systems.

825 citations


Journal ArticleDOI
01 Apr 2012
TL;DR: A model examining motives of consumers' eWOM intention is developed and reputation, sense of belonging, and enjoyment of helping are significant factors, and the model explains 69 percent of the variance.
Abstract: The advance of the Internet facilitates consumers to share and exchange consumption-related advice through online consumer reviews. This relatively new form of word-of-mouth communication, electronic word-of-mouth (eWOM) communication, has only recently received significant managerial and academic attention. Many academic studies have looked at the effectiveness of positive eWOM communication, examining the process by which eWOM influences consumer purchasing decisions. eWOM behavior is primarily explained from the individual rational perspective that emphasizes a cost and benefit analysis. However, we felt there was a need for an extensive study that examines consumers' motives for eWOM. In this paper, we focus on the factors that drive consumers to spread positive eWOM in online consumer-opinion platforms. Building on the social psychology literature, we identified a number of key motives of consumers' eWOM intention and developed an associated model. We empirically tested the research model with a sample of 203 members of a consumer review community, OpenRice.com. The model explains 69% of the variance, with reputation, sense of belonging and enjoyment of helping other consumers significantly related to consumers' eWOM intention. The results of this study provide important implications for research and practice. Highlights? In this study, we developed a model examining motives of consumers' eWOM intention. ? We tested the model with a sample of 203 members of a consumer review community. ? The model explains 69 percent of the variance. ? Reputation, sense of belonging, and enjoyment of helping are significant factors.

781 citations


Journal ArticleDOI
31 Jan 2012-BMJ
TL;DR: When patients with cancer other than breast cancer were also included, physical activity was associated with reduced BMI and body weight, increased peak oxygen consumption and peak power output, and improved quality of life.
Abstract: Objective To systematically evaluate the effects of physical activity in adult patients after completion of main treatment related to cancer. Design Meta-analysis of randomised controlled trials with data extraction and quality assessment performed independently by two researchers. Data sources Pubmed, CINAHL, and Google Scholar from the earliest possible year to September 2011. References from meta-analyses and reviews. Study selection Randomised controlled trials that assessed the effects of physical activity in adults who had completed their main cancer treatment, except hormonal treatment. Results There were 34 randomised controlled trials, of which 22 (65%) focused on patients with breast cancer, and 48 outcomes in our meta-analysis. Twenty two studies assessed aerobic exercise, and four also included resistance or strength training. The median duration of physical activity was 13 weeks (range 3-60 weeks). Most control groups were considered sedentary or were assigned no exercise. Based on studies on patients with breast cancer, physical activity was associated with improvements in insulin-like growth factor-I, bench press, leg press, fatigue, depression, and quality of life. When we combined studies on different types of cancer, we found significant improvements in body mass index (BMI), body weight, peak oxygen consumption, peak power output, distance walked in six minutes, right handgrip strength, and quality of life. Sources of study heterogeneity included age, study quality, study size, and type and duration of physical activity. Publication bias did not alter our conclusions. Conclusions Physical activity has positive effects on physiology, body composition, physical functions, psychological outcomes, and quality of life in patients after treatment for breast cancer. When patients with cancer other than breast cancer were also included, physical activity was associated with reduced BMI and body weight, increased peak oxygen consumption and peak power output, and improved quality of life.

687 citations


Journal ArticleDOI
TL;DR: Experimental results show that the proposed method outperforms the existing methods, in terms of image quality and recognition accuracy, as well as face super-resolution methods.
Abstract: This paper addresses the very low resolution (VLR) problem in face recognition in which the resolution of the face image to be recognized is lower than 16 × 16. With the increasing demand of surveillance camera-based applications, the VLR problem happens in many face application systems. Existing face recognition algorithms are not able to give satisfactory performance on the VLR face image. While face super-resolution (SR) methods can be employed to enhance the resolution of the images, the existing learning-based face SR methods do not perform well on such a VLR face image. To overcome this problem, this paper proposes a novel approach to learn the relationship between the high-resolution image space and the VLR image space for face SR. Based on this new approach, two constraints, namely, new data and discriminative constraints, are designed for good visuality and face recognition applications under the VLR problem, respectively. Experimental results show that the proposed SR algorithm based on relationship learning outperforms the existing algorithms in public face databases.

467 citations


Journal ArticleDOI
TL;DR: This paper proposes to linearize the ALM and the ADM for some nuclear norm involved minimization problems such that closed-form solutions of these linearized subproblems can be easily derived.
Abstract: The nuclear norm is widely used to induce low-rank solutions for many optimization problems with matrix variables. Recently, it has been shown that the augmented Lagrangian method (ALM) and the alternating direction method (ADM) are very efficient for many convex programming problems arising from various applications, provided that the resulting subproblems are sufficiently simple to have closed-form solutions. In this paper, we are interested in the application of the ALM and the ADM for some nuclear norm involved minimization problems. When the resulting subproblems do not have closed-form solutions, we propose to linearize these subproblems such that closed-form solutions of these linearized subproblems can be easily derived. Global convergence of these linearized ALM and ADM are established under standard assumptions. Finally, we verify the effectiveness and efficiency of these new methods by some numerical experiments.

387 citations


Journal ArticleDOI
TL;DR: Experiences sampling and daily diary (ESM/DD) research elicits repeated reports of immediate or very recent experiences from the same sample of people for several days or weeks as discussed by the authors, which are helpful in studying dynamic within-person processes involving affect, behavior, interpersonal interactions, work events, and other transient workplace phenomena over time.
Abstract: Summary Experience sampling methodology and daily diary (ESM/DD) research elicits repeated reports of immediate or very recent experiences from the same sample of people for several days or weeks. Experience sampling and diary methods were almost unheard of in organizational research 15 years ago, but the past decade has seen a rapid rise in their use. These methods are helpful in studying dynamic within-person processes involving affect, behavior, interpersonal interactions, work events, and other transient workplace phenomena over time. Assessing cross-level effects of traits or other stable features on within-person processes and reactivity is also possible with ESM/DD data. We provide an introduction to issues in designing and carrying out an ESM/DD study, including data collection choices and schedules, measures, technology, training and motivation of participants, and analysis of multilevel data. We offer best practice recommendations and refer readers to further resources for additional detail on conducting and analyzing ESM/DD research. Copyright © 2012 John Wiley & Sons, Ltd.

376 citations


Journal ArticleDOI
01 Feb 2012-EPL
TL;DR: It is found that the stronger the bias in the utility function, the higher the level of public cooperation and cooperation is promoted because the aggressive invasion of defectors is more sensitive to the slowing-down than the build-up of collective efforts in sizable groups.
Abstract: We study the evolution of public cooperation on two interdependent networks that are connected by means of a utility function, which determines to what extent payoffs in one network influence the success of players in the other network. We find that the stronger the bias in the utility function, the higher the level of public cooperation. Yet the benefits of enhanced public cooperation on the two networks are just as biased as the utility functions themselves. While cooperation may thrive on one network, the other may still be plagued by defectors. Nevertheless, the aggregate level of cooperation on both networks is higher than the one attainable on an isolated network. This positive effect of biased utility functions is due to the suppressed feedback of individual success, which leads to a spontaneous separation of characteristic time scales of the evolutionary process on the two interdependent networks. As a result, cooperation is promoted because the aggressive invasion of defectors is more sensitive to the slowing-down than the build-up of collective efforts in sizable groups.

Journal ArticleDOI
TL;DR: An extremely high-efficiency solution-processed white organic light-emitting diode (WOLED) is successfully developed by simultaneously using an ideal dendritic host material and a novel efficient orange phosphorescent iridium complex, promising the low-cost solution- Processed WOLEDs a bright future as the next generation of illumination sources.
Abstract: An extremely high-efficiency solution-processed white organic light-emitting diode (WOLED) is successfully developed by simultaneously using an ideal dendritic host material and a novel efficient orange phosphorescent iridium complex. The optimized device exhibits forward-viewing efficiencies of 70.6 cd A(-1) , 26.0%, and 47.6 lm W(-1) at a luminance of 100 cd m(-2) , respectively, promising the low-cost solution-processed WOLEDs a bright future as the next generation of illumination sources.

Journal ArticleDOI
TL;DR: Results indicate (AspSerSer)6-liposome as a promising targeted delivery system for RNA interference–based bone anabolic therapy and markedly promoted bone formation, enhanced the bone micro-architecture and increased the bone mass in both healthy and osteoporotic rats.
Abstract: Zhang and colleagues have developed a new targeted delivery system for RNA interference–based bone anabolic therapy. Using dioleoyl trimethylammonium propane (DOTAP)-based cationic liposomes attached to six repetitive sequences of aspartate, serine, serine (AspSerSer)6, the system provided selective enrichment of the encapsulated osteogenic siRNA in osteogenic lineage cells at the bone formation surface and the subsequent depletion of the target gene, encoding the bone formation inhibitor casein kinase-2 interacting protein-1 (PLEKHO1, also known as CKIP-1), leading to the promotion of bone formation in healthy and osteoporotic rats.

Journal ArticleDOI
TL;DR: This paper surveys the state of the art of user experience research in RS by examining how researchers have evaluated design methods that augment RS’s ability to help users find the information or product that they truly prefer, interact with ease with the system, and form trust with RS through system transparency, control and privacy preserving mechanisms.
Abstract: A recommender system is a Web technology that proactively suggests items of interest to users based on their objective behavior or explicitly stated preferences. Evaluations of recommender systems (RS) have traditionally focused on the performance of algorithms. However, many researchers have recently started investigating system effectiveness and evaluation criteria from users' perspectives. In this paper, we survey the state of the art of user experience research in RS by examining how researchers have evaluated design methods that augment RS's ability to help users find the information or product that they truly prefer, interact with ease with the system, and form trust with RS through system transparency, control and privacy preserving mechanisms finally, we examine how these system design features influence users' adoption of the technology. We summarize existing work concerning three crucial interaction activities between the user and the system: the initial preference elicitation process, the preference refinement process, and the presentation of the system's recommendation results. Additionally, we will also cover recent evaluation frameworks that measure a recommender system's overall perceptive qualities and how these qualities influence users' behavioral intentions. The key results are summarized in a set of design guidelines that can provide useful suggestions to scholars and practitioners concerning the design and development of effective recommender systems. The survey also lays groundwork for researchers to pursue future topics that have not been covered by existing methods.

Journal ArticleDOI
TL;DR: In this paper, a simple-to-implement panel data method was proposed to evaluate the impacts of social policy on Hong Kong's economic growth by exploiting the dependence among cross-sectional units to construct the counterfactuals.
Abstract: SUMMARY We propose a simple-to-implement panel data method to evaluate the impacts of social policy. The basic idea is to exploit the dependence among cross-sectional units to construct the counterfactuals. The cross-sectional correlations are attributed to the presence of some (unobserved) common factors. However, instead of trying to estimate the unobserved factors, we propose to use observed data. We use a panel of 24 countries to evaluate the impact of political and economic integration of Hong Kong with mainland China. We find that the political integration hardly had any impact on the growth of the Hong Kong economy. However, the economic integration has raised Hong Kong's annual real GDP by about 4%. Copyright © 2011 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: Zhang et al. as discussed by the authors examined the relationship between workplace ostracism and employee psychological distress by focusing on the joint moderating effects of ingratiation and political skill, and found that when employee political skill was high, ingratiati neutralized the relationship and when it was low, it exacerbated the relationship.
Abstract: The study reported here examined the relationship between workplace ostracism and employee psychological distress (i.e. job tension, emotional exhaustion, and depressed mood at work) by focusing on the joint moderating effects of ingratiation and political skill. Data from a two-wave survey of 215 employees in two oil and gas firms in China indicated that as predicted, workplace ostracism was positively related to psychological distress. Moreover, the findings showed that when employee political skill was high, ingratiation neutralized the relationship between workplace ostracism and psychological distress, but when it was low, ingratiation exacerbated the relationship.

Journal ArticleDOI
06 Dec 2012-Neuron
TL;DR: Evidence is found that stochastic antidromic spikes originating from the STN directly modify the firing probability of the corticofugal projection neurons, destroy the dominance of beta rhythm, and thus restore motor control to the subjects, be they patients or rodents.

Journal ArticleDOI
TL;DR: Luminescent metal complexes have attracted increasing attention in the literature over the last few decades as discussed by the authors, and transition metal compounds have been widely studied for luminescent sensing applications due to their attractive photophysical properties.

Journal ArticleDOI
TL;DR: A hybrid framework is developed to unify the advantages of different methods and overcome their respective limitations, indicating how hybrid critiquing supports could effectively enable end-users to achieve more confident decisions.
Abstract: Critiquing-based recommender systems elicit users' feedback, called critiques, which they made on the recommended items. This conversational style of interaction is in contract to the standard model where users receive recommendations in a single interaction. Through the use of the critiquing feedback, the recommender systems are able to more accurately learn the users' profiles, and therefore suggest better recommendations in the subsequent rounds. Critiquing-based recommenders have been widely studied in knowledge-, content-, and preference-based recommenders and are beginning to be tried in several online websites, such as MovieLens. This article examines the motivation and development of the subject area, and offers a detailed survey of the state of the art concerning the design of critiquing interfaces and development of algorithms for critiquing generation. With the help of categorization analysis, the survey reveals three principal branches of critiquing based recommender systems, using respectively natural language based, system-suggested, and user-initiated critiques. Representative example systems will be presented and analyzed for each branch, and their respective pros and cons will be discussed. Subsequently, a hybrid framework is developed to unify the advantages of different methods and overcome their respective limitations. Empirical findings from user studies are further presented, indicating how hybrid critiquing supports could effectively enable end-users to achieve more confident decisions. Finally, the article will point out several future trends to boost the advance of critiquing-based recommenders.

Journal ArticleDOI
TL;DR: The results indicate that a tri-modal nanoprobe served as fluorescent/CT/magnetic bioimaging can be realized using the PEG-modified BaGdF₅:Yb/Er UCNPs with very low cytotoxicity and long circulation time, which would be very useful in a variety of biomedical application fields.

Journal ArticleDOI
TL;DR: Underpinning the fundamental requirements for effectively forming Au-Fe(x)O(y) hybrid nanocomposite materials would shed light on future development of nanotheranostics, nanomedicines, and chemical technologies.
Abstract: This critical review provides an overview of current research activities that focused on the synthesis and application of multi-functional gold and iron oxide (Au–FexOy) hybrid nanoparticles and nanocomposites An introduction of synthetic strategies that have been developed for generating Au–FexOy nanocomposites with different nanostructures is presented Surface functionalisation and bioconjugation of these hybrid nanoparticles and nanocomposites are also reviewed A variety of applications such as theranostics, gene delivery, biosensing, cell sorting, bio-separation, and catalysis is discussed and highlighted Finally, future trends and perspectives of these sophisticated nanocomposites are outlined Underpinning the fundamental requirements for effectively forming Au–FexOy hybrid nanocomposite materials would shed light on future development of nanotheranostics, nanomedicines, and chemical technologies It would be interesting to investigate such multi-component composite nanomaterials with different novel morphologies in the near future to advance chemistry, biology, medicine, and engineering multi-disciplinary research (120 references)

Journal ArticleDOI
TL;DR: In this paper, a robust rank correlation screening (RRCS) method is proposed to deal with ultra-high dimensional data, which is based on the Kendall correlation coefficient between response and predictor variables rather than the Pearson correlation.
Abstract: Independence screening is a variable selection method that uses a ranking criterion to select significant variables, particularly for statistical models with nonpolynomial dimensionality or “large $p$, small $n$” paradigms when $p$ can be as large as an exponential of the sample size $n$. In this paper we propose a robust rank correlation screening (RRCS) method to deal with ultra-high dimensional data. The new procedure is based on the Kendall $\tau$ correlation coefficient between response and predictor variables rather than the Pearson correlation of existing methods. The new method has four desirable features compared with existing independence screening methods. First, the sure independence screening property can hold only under the existence of a second order moment of predictor variables, rather than exponential tails or alikeness, even when the number of predictor variables grows as fast as exponentially of the sample size. Second, it can be used to deal with semiparametric models such as transformation regression models and single-index models under monotonic constraint to the link function without involving nonparametric estimation even when there are nonparametric functions in the models. Third, the procedure can be largely used against outliers and influence points in the observations. Last, the use of indicator functions in rank correlation screening greatly simplifies the theoretical derivation due to the boundedness of the resulting statistics, compared with previous studies on variable screening. Simulations are carried out for comparisons with existing methods and a real data example is analyzed.

Journal ArticleDOI
TL;DR: This paper considers the linearly constrained separable convex programming, whose objective function is separable into m individual convex functions without coupled variables, and shows the global convergence of this extension when the involved functions are further assumed to be strongly convex.
Abstract: We consider the linearly constrained separable convex programming, whose objective function is separable into m individual convex functions without coupled variables. The alternating direction method of multipliers has been well studied in the literature for the special case m=2, while it remains open whether its convergence can be extended to the general case m≥3. This note shows the global convergence of this extension when the involved functions are further assumed to be strongly convex.

Journal ArticleDOI
TL;DR: Analysis of bacterial 16S rDNA of the composting mass indicated that the addition of antibiotics up to 100, 20 and 20mg/kg of chlortetracycline, sulfadiazine and ciprofloxacin elicited only a transient perturbation and the bacterial diversity was restored in due course of composting, indicating that composting is a potential method of manure management.

Journal ArticleDOI
TL;DR: In this paper, 3D macroporous (3DOM) single-phase rhombohedral perovskite-type oxide LaMnO3 materials with nanovoid skeletons were prepared using the poly(methyl methacrylate)-templating methods with the assistance of surfactant (poly(ethylene glycol) (PEG) or triblock copolymer (Pluronic P123)).

Journal ArticleDOI
TL;DR: In this article, the photocatalytic activity of Bi2O2CO3/BiOI composites was evaluated through the photocleaning of wastewater which contained rhodamine-B, methylene blue, crystal violet, or a mixture of them under visible-light irradiation (λ ≥ 420 nm).
Abstract: Bi2O2CO3/BiOI composites were fabricated at room temperature for the first time by a facile method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis DRS), and nitrogen adsorption–desorption techniques were employed to characterize the physiochemical properties of the composites. The photocatalytic activities of Bi2O2CO3, BiOI, and Bi2O2CO3/BiOI were evaluated through the photocleaning of wastewater which contained rhodamine-B, methylene blue, crystal violet, or a mixture of them under visible-light irradiation (λ ≥ 420 nm). The photocatalytic activity of Bi2O2CO3/BiOI is much higher than that of its components. Moreover, the composite shows good photostability and recyclability. The excellent catalytic efficiency of the Bi2O2CO3/BiOI composite is deduced closely related to Bi2O2CO3/BiOI heterojunctions whose presence is generally regarded to be a favorable factor for the s...

Journal ArticleDOI
15 May 2012-Talanta
TL;DR: The AuNPs-β-CD-Gra-modified glassy carbon electrode (GCE) has been successfully applied to determine UA in human urine with satisfactory results and provides a simple, convenient and green route to synthesize AuNps on Gra which is potentially useful in electroanalysis.

Journal ArticleDOI
27 Feb 2012-Rice
TL;DR: The biological functions of ABA in response to different stresses are summarized, especially the roles of Aba in plant defense to pathogen attack, and the possible relationships of these determinants in controlling the specificity and intensity of A BA signaling pathway in the rice are discussed.
Abstract: Ever since its discovery, abscisic acid (ABA) has been intensively studied due to its versatile functions in plant developmental and physiological processes. Many signaling details of ABA have been well elucidated and reviewed. The identification of ABA receptors is a great breakthrough in the field of ABA study, whereas the discovery of ABA transporter has changed our concept that ABA is delivered solely by passive transport. The intensity of ABA signaling pathway is well known to be controlled by multi-regulators. Nonetheless, the interaction and coordination among ABA biosynthesis, catabolism, conjugation and transportation are seldom discussed. Here, we summarize the biological functions of ABA in response to different stresses, especially the roles of ABA in plant defense to pathogen attack, and discuss the possible relationships of these determinants in controlling the specificity and intensity of ABA signaling pathway in the rice.

Journal ArticleDOI
TL;DR: This paper found that consumers with high self-brand connections (SBC) respond to negative brand information as they do to personal failure and experience a threat to their positive self-view.

Journal ArticleDOI
TL;DR: It is found that sparsity may favor the resolution of social dilemmas, especially if the population density is close to the percolation threshold of the underlying graph.
Abstract: Spatial reciprocity is a well known tour de force of cooperation promotion. A thorough understanding of the effects of different population densities is therefore crucial. Here we study the evolution of cooperation in social dilemmas on different interaction graphs with a certain fraction of vacant nodes. We find that sparsity may favor the resolution of social dilemmas, especially if the population density is close to the percolation threshold of the underlying graph. Regardless of the type of the governing social dilemma as well as particularities of the interaction graph, we show that under pairwise imitation the percolation threshold is a universal indicator of how dense the occupancy ought to be for cooperation to be optimally promoted. We also demonstrate that myopic updating, due to the lack of efficient spread of information via imitation, renders the reported mechanism dysfunctional, which in turn further strengthens its foundations.