The effect of realistic geometries on the susceptibility-weighted MR signal in white matter

Purpose: To investigate the effect of realistic microstructural geometry on the susceptibility-weighted magnetic resonance (MR) signal in white matter (WM), with application to demyelination. Methods: Previous work has modeled susceptibility-weighted signals under the assumption that axons are cylindrical. In this work, we explore the implications of this assumption by considering the effect of more realistic geometries. A three-compartment WM model incorporating relevant properties based on literature was used to predict the MR signal. Myelinated axons were modeled with several cross-sectional geometries of increasing realism: nested circles, warped/elliptical circles and measured axonal geometries from electron micrographs. Signal simulations from the different microstructural geometries were compared to measured signals from a Cuprizone mouse model with varying degrees of demyelination. Results: Results from simulation suggest that axonal geometry affects the MR signal. Predictions with realistic models were significantly different compared to circular models under the same microstructural tissue properties, for simulations with and without diffusion. Conclusion: The geometry of axons affects the MR signal significantly. Literature estimates of myelin susceptibility, which are based on fitting biophysical models to the MR signal, are likely to be biased by the assumed geometry, as will any derived microstructural properties.Comment: Accepted March 4 2017, in publication at Magnetic Resonance in Medicin

The Value of Information Technology in E-Business Environments: The Missing Links in the Renewed IT Value Debate

After more than a decade of intensive studies, business value of information technology continues to generate interest and debate among both academics and practitioners. Drawing upon the IT value literature and the resource-based view of the firm, we develop a process-oriented model of IT value creation in the context of electronic business. Instead of a dichotomous measure of “adoption vs. non-adoption” as typically found in the literature, this model incorporates three stages (investment–usage–value) of the diffusion process at the firm level, with actual usage being an important mediating variable. The model also includes both IT resources and organizational factors, and tests the complementarity between them. A large-scale international dataset, involving 2,139 firms from 10 countries, is used to test the theoretical model. After controlling for firm size and industry effects, our empirical analyses based on structural equation modeling have shown that the investment–usage–value linkages are significant (although the direct link between investment and value is weak), suggesting that usage would be a “missing link” if not included. Another finding is that, while IT still matters (especially deeper use of IT such as back-end integration), complementary organizational resources (e.g., management support and external relationships) are found to be highly significant in creating value from e-business investment. On the other hand, these relationships tend to be moderated by environmental factors. These findings contribute to the ongoing debate over IT value—in this case, the value of Internet technologies in the e-business environment. They also offer important implications for the way firms approach IT investment and management in the post-bubble Internet era

Direct observation of magnon-phonon coupling in yttrium iron garnet

The magnetic insulator yttrium iron garnet (YIG) with a ferrimagnetic transition temperature of $\sim$560 K has been widely used in microwave and spintronic devices. Anomalous features in the spin Seeback effect (SSE) voltages have been observed in Pt/YIG and attributed to the magnon-phonon coupling. Here we use inelastic neutron scattering to map out low-energy spin waves and acoustic phonons of YIG at 100 K as a function of increasing magnetic field. By comparing the zero and 9.1 T data, we find that instead of splitting and opening up gaps at the spin wave and acoustic phonon dispersion intersecting points, magnon-phonon coupling in YIG enhances the hybridized scattering intensity. These results are different from expectations of conventional spin-lattice coupling, calling for new paradigms to understand the scattering process of magnon-phonon interactions and the resulting magnon-polarons.Comment: 5 pages, 4 figures, PRB in pres

Assessing Drivers of E-Business Value: Results of a Cross-Country Study

This study seeks to better understand the facors that contribute to value creation of e-business. Grounded in the technology-organization-environment (TOE) framework, we developed a research model for assessing the value of e-business at the firm level. Based on this framework, we formulated six hypotheses and identified six factors (technology integration, firm size, firm scope, financial resources, competition intensity, and regulatory environment) that may affect value creation of e-business. Survey data of 612 firms across 10 countries in the financial services industry were collected and used to test the theoretical model. To examine how e-business value is influenced by national environments, we compared two subsamples from developed and developing countries. Structural equation modeling demonstrated several key findings: (1) Within the TOE framework, technology integration emerges as the strongest factor for e-business value, while financial resources, firm scope, and regulatory environment also significantly contribute to e-business value. (2) Firm size is negatively related to e-business value, suggesting that structural inertia associated with large firms tends to retard e- business value. (3) Competitive pressure often drives firms to adopt e-business, but e-business value originates more from internal organizational resources (e.g., technological integration) than from external pressure. (4) Government regulation plays a much more important role in developing countries than in developed countries. These findings indicate the usefulness of the TOE framework and our research model for studying e-business value

A Cross-Country Study of Electronic Business Adoption Using the Technology-Organization-Environment Framework

In this study, we developed a conceptual model for electronic business (e-business or EB) adoption incorporating six adoption facilitators and inhibitors, based on the technology-organization-environment framework. Survey data from 3,100 businesses and 7,500 consumers in eight European countries were used to test the model. We conducted confirmatory factor analysis to assess the reliability and validity of constructs. To examine whether adoption behaviors differ across different e-business environments, we divided the full sample into high EB-intensity and low EB-intensity countries. The fitted logit models demonstrated four findings: (1) Technology competence, firm scope and size, consumer readiness, and competitive pressure are significant adoption drivers, while lack of trading partner readiness is a significant adoption inhibitor. (2) As EB-intensity increases, two environmental factorsóconsumer readiness and lack of trading partner readinessóbecome less important. (3) In high EB-intensity countries, e-business is no longer a phenomenon dominated by large firms; as more and more firms engage in e-business, network effect works to the advantage of small firms. (4) Firms are more cautious into adopting e-business in high EB-intensity countries, which seems to suggest that the more informed firms are less aggressive into adopting e-business

How Do Social Media Shape the Information Environment in the Financial Market?

Internet users create social media that enable information to be transferred more efficiently. In this work we focus on a typical social media platform Wikipedia and examine how management’s voluntary disclosure reacts to information arrivals on Wikipedia. In doing so, we seek to answer the question of whether social media indeed improve the information environment for investors in the financial market. Our analysis is based on a unique dataset collected from the modification history of firm entries on Wikipedia, and thus we are able to identify information arrivals on Wikipedia. We find that information arrivals on Wikipedia affect the timing of management disclosure of bad news, and the effect is in sharp contrast to the way in which traditional media affect management disclosure. Further, we find consistent evidence that information arrivals on Wikipedia preempt the negative reaction of the market to bad news. In contrast, more news coverage in traditional media exacerbates the problem of optimistic analyst forecasts. Together these findings emphasize that social media have an identifiable effect on both the management side and the investor side in the financial market

Abelian repetitions in partial words

AbstractWe study abelian repetitions in partial words, or sequences that may contain some unknown positions or holes. First, we look at the avoidance of abelian pth powers in infinite partial words, where p>2, extending recent results regarding the case where p=2. We investigate, for a given p, the smallest alphabet size needed to construct an infinite partial word with finitely or infinitely many holes that avoids abelian pth powers. We construct in particular an infinite binary partial word with infinitely many holes that avoids 6th powers. Then we show, in a number of cases, that the number of abelian p-free partial words of length n with h holes over a given alphabet grows exponentially as n increases. Finally, we prove that we cannot avoid abelian pth powers under arbitrary insertion of holes in an infinite word

Multimodal Data Augmentation for Image Captioning using Diffusion Models

Image captioning, an important vision-language task, often requires a tremendous number of finely labeled image-caption pairs for learning the underlying alignment between images and texts. In this paper, we proposed a multimodal data augmentation method, leveraging a recent text-to-image model called Stable Diffusion, to expand the training set via high-quality generation of image-caption pairs. Extensive experiments on the MS COCO dataset demonstrate the advantages of our approach over several benchmark methods, and particularly a significant boost when having fewer training instances. In addition, models trained on our augmented datasets also outperform prior unpaired image captioning methods by a large margin. Finally, further improvement regarding the training efficiency and effectiveness can be obtained after intentionally filtering the generated data based on quality assessment

‘Mingren are the respectable ones’: An analysis of everyday engagements with contemporary celebrity culture in China

To investigate the values and social norms underpinning celebrity culture, it is crucial to study everyday uses of celebrity culture. Yet, studies in this area have been limited thus far, especially in non-Western contexts. This exploratory study focuses on the ways how young and middle-aged adults in everyday life in urban China discuss and value media celebrities. The results show that respondents have a rather similar way of valuing celebrity: celebrities need to have strong work ethics and showcase social responsibility; only then do they ‘earn’ their right to be considered ‘famous’. We conclude that these values are closely related to the current socio-cultural situation of China’s social transformation and echo the value system promoted by the Chinese government