Wheel and Star-critical Ramsey Numbers for Quadrilateral

The star-critical Ramsey number r∗(H1, H2) is the smallest integer k such that every red/blue coloring of the edges of Kn − K1,n−k−1 contains either a red copy of H1 or a blue copy of H2, where n is the graph Ramsey number R(H1, H2). We study the cases of r∗(C4, Cn) and R(C4, Wn). In particular, we prove that r∗(C4, Cn) = 5 for all n \u3e 4, obtain a general characterization of Ramsey-critical (C4, Wn)-graphs, and establish the exact values of R(C4, Wn) for 9 cases of n between 18 and 44

Virtual Collaboration with Mobile Social Media in Multiple-Organization Projects

This study investigates the use of mobile social media as emerging collaboration tools by virtual teams. Based on the construal level theory, it develops a research model hypothesizes that collaboration tool effectiveness influence contextual performance and task performance through the mediation of procedure agreeability. In addition, geographic dispersion, team size and project duration serve as moderators as they reflect virtual collaboration complexity. Empirical findings support most hypothesized relationships. Theoretical and practical implications are discussed

Contextual and Organizational Factors in Sustainable Supply Chain Decision-Making: Grey Relational Analysis and Interpretative Structural Modeling

Sustainable supply chain emerges as a major business trend essential to long-term competitive advantage. Relevant corporate decisions concern a broad range of factors and require novel analytical models for critical control. This study conducts mathematical analyses to identify the factors that are vital yet receiving insufficient attention from researchers and practitioners. Valid survey observations were collected from 113 enterprises in China, the biggest emerging economy that faces the dilemma between development and sustainability. Grey relational analysis (GRA) and interpretative structural modeling (ISM) assess the importance levels of contextual and organizational factors and explore their joint effects. Validated with conventional expert interviews, the results prioritize the factors that play crucial roles in sustainable supply chains. In particular, enterprises should pay close attention to three factors: corporate collaboration, clean production and supplier selection, which provide useful clues on the best practices of formulating low-carbon decisions. With a better understanding of critical factors, enterprises may make supply chains more sustainable with limited resources. To enhance the generalizability of findings, future studies may collect more observations from multiple countries and validate the results in the settings of global supply chains

miR-181a increases FoxO1 acetylation and promotes granulosa cell apoptosis via SIRT1 downregulation.

Oxidative stress impairs follicular development by inducing granulosa cell (GC) apoptosis, which involves enhancement of the transcriptional activity of the pro-apoptotic factor Forkhead box O1 (FoxO1). However, the mechanism by which oxidative stress promotes FoxO1 activity is still unclear. Here, we found that miR-181a was upregulated in hydrogen peroxide (

Synergy between Green Supply Chain Management and Green Information Systems on Corporate Sustainability: An Informal Alignment Perspective

At the corporate level, green innovation is essential for environment protection and sustainable development. Green supply chain management (GSCM) and green information system (GIS) are two important pillars of green innovation. This study investigates the possible alignment between them in terms of the synergistic effect on corporate sustainability. Based on the task-technology fit model, GSCM and GIS can be viewed as the task- and technology-side endeavors. The extant conceptualization of the fit between a task and a technology assumes their interdependence, but efficiency-oriented GSCM and technology-driven GIS are relatively independent from each other as they can be carried out separately. Formed on the basis of spontaneous employee participation in both, their alignment is rather informal than formal. Unlike the regular task-technology fit from a top-down arrangement, such a bottom-up alignment is not the necessary condition for GSCM and GIS to take effects, but adds to their direct impacts on green innovation outcome in a one-plus-one-greater-than-two manner. Survey observations gathered from over 300 organizations in China confirm that the informal alignment between GSCM and GIS enhances economic, operational, environmental and social performances on top of their primary contributions. The findings regarding the synergy between GSCM and GIS on corporate sustainability provide researchers and practitioners helpful insights on how to optimize green innovation effectiveness

Flexible versus simple trade-in strategy for remanufacturing

Some enterprises recently start to offer the flexible trade-in option to attract customers from competitors, in contrast to the simple one that only allows them to return used products to the same manufacturers for new. Based on analytical and numerical analyses, this study compares the environmental impacts of two trade-in strategies (simple versus flexible) in combination with different carbon tax policies. From the perspective of consumer switching behaviour, a Hotelling model with two market segments is established. Under the flexible trade-in strategy, the carbon emission of enterprises turns out to be significantly higher than that under the simple trade-in strategy. An appropriate carbon tax policy, especially with preferential tax rates on green products, is capable of guiding enterprises to choose a more environment-friendly trade-in strategy included in the model. The findings fill the research gap in comparing the pros and cons of simple and flexible trade-in strategies in terms of sustainable development, and provide managers and policy-makers the insights on how to promote the healthy development of the remanufacturing industry with trade-in strategizing and carbon taxation

Sharing economy of electric vehicle private charge posts

The increasing popularity of electric vehicles (EVs) leads to heightened demand for the charging infrastructure. More and more EV drivers install private charge posts, which can now be shared with others through certain mobile apps. This emerging phenomenon is becoming a prominent part of the sharing economy. To examine the impacts of post sharing on EV charging market, this study establishes game theory models on consumer choices among private, public, and shared options. Such peer-to-peer sharing and collaborative consumption redistribute the installation and operation costs of private charge posts in proportion to their increased utilization. Numerical analyses suggest that the sharing mode provides a win-win solution for charge post owners and non-owner consumers, as well as electricity distributors and public charging infrastructure operators. In the case of China, the estimated saving for charge post owners is between 20% and 50%, which can be translated into more non-government investment in the EV industry chain. The findings provide supporting evidence for policy-makers to promote private charge post sharing, especially with certain consumer subsidization at a reasonable level

Mobile social media in inter-organizational projects: Aligning tool, task and team for virtual collaboration effectiveness

Inter-organizational projects face unique challenges and opportunities due to team diversities and task complexity. Mobile social media like WhatsApp and WeChat emerge as new-generation collaboration tools in such endeavors. Based on a literature review, this study posits that how well team-tool, task-tool and team-task relationships are handled shape virtual collaboration effectiveness. The conceptual framework, validated with the interviews from inter-organizational project team members in China and the USA, leads to a research model. The results of a larger-scale survey confirm that tool usability, task fit and team connectivity contribute to virtual collaboration effectiveness, which affects project management success and team appreciation. In addition, there are noticeable cross-country differences, especially the opposite moderating effects that degree of use imposes on the relationship between virtual collaboration effectiveness and project management success. Theoretical and practical implications of the findings are discussed