On the Radio Detectability of Circumplanetary Discs

Discs around young planets, so-called circumplanetary discs (CPDs), are essential for planet growth, satellite formation, and planet detection. We study the millimetre and centimetre emission from accreting CPDs by using the simple α disc model. We find that it is easier to detect CPDs at shorter radio wavelengths (e.g. λ ≲ 1 mm). For example, if the system is 140 pc away from us, deep observations (e.g. 5 h) at ALMA Band 7 (0.87 mm) are sensitive to as small as 0.03 lunar mass of dust in CPDs. If the CPD is around a Jupiter mass planet 20 au away from the host star and has a viscosity parameter α ≲ 0.001, ALMA can detect this disc when it accretes faster than 10−10M⊙yr−110−10M⊙yr−1 . ALMA can also detect the \u27minimum mass sub-nebulae\u27 disc if such a disc exists around a young planet in young stellar objects. However, to distinguish the embedded compact CPD from the circumstellar disc material, we should observe circumstellar discs with large gaps/cavities using the highest resolution possible. We also calculate the CPD fluxes at VLA bands, and discuss the possibility of detecting radio emission from jets/winds launched in CPDs. Finally we argue that, if the radial drift of dust particles is considered, the drifting time-scale for millimetre dust in CPDs can be extremely short. It only takes 102–103 yr for CPDs to lose millimetre dust. Thus, for CPDs to be detectable at radio wavelengths, mm-sized dust in CPDs needs to be replenished continuously, or the disc has a significant fraction of micron-sized dust or a high gas surface density so that the particle drifting time-scale is long, or the radial drift is prevented by other means (e.g. pressure traps)

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

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

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

Targeted expression of cyclin D2 ameliorates late stage anthracycline cardiotoxicity

Aims Doxorubicin (DOX) is a widely used and effective anti-cancer therapeutic. DOX treatment is associated with both acute and late onset cardiotoxicity, limiting its overall efficacy. Here, the impact of cardiomyocyte cell cycle activation was examined in a juvenile model featuring aspects of acute and late onset DOX cardiotoxicity. Methods and results Two-week old MHC-cycD2 transgenic mice (which express cyclin D2 in postnatal cardiomyocytes and exhibit sustained cardiomyocyte cell cycle activity; D2 mice) and their wild type (WT) littermates received weekly DOX injections for 5 weeks (25 mg/kg cumulative dose). One week after the last DOX treatment (acute stage), cardiac function was suppressed in both groups. Acute DOX cardiotoxicity in D2 and WT mice was associated with similar increases in the levels of cardiomyocyte apoptosis and Ku70/Ku80 expression (markers of DNA damage and oxidative stress), as well as similar reductions in hypertrophic cardiomyocyte growth. Cardiac dysfunction persisted in WT mice for 13 weeks following the last DOX treatment (late stage) and was accompanied by increased levels of cardiomyocyte apoptosis, Ku expression, and myocardial fibrosis. In contrast, D2 mice exhibited a progressive recovery in cardiac function, which was indistinguishable from saline-treated animals by 9 weeks following the last DOX treatment. Improved cardiac function was accompanied by reductions in the levels of late stage cardiomyocyte apoptosis, Ku expression, and myocardial fibrosis. Conclusion These data suggest that cardiomyocyte cell cycle activity can promote recovery of cardiac function and preserve cardiac structure following DOX treatment

Maintenance of heterocyst patterning in a filamentous cyanobacterium

In the absence of sufficient combined nitrogen, some filamentous cyanobacteria differentiate nitrogenfixing heterocysts at approximately every 10th cell position. As cells between heterocysts grow and divide, this initial pattern is maintained by the differentiation of a single cell approximately midway between existing heterocysts. This paper introduces a mathematical model for the maintenance of the periodic pattern of heterocysts differentiated by Anabaena sp. strain PCC 7120 based on the current experimental knowledge of the system. The model equations describe a non-diffusing activator (HetR) and two inhibitors (PatS and HetN) that undergo diffusion in a growing one-dimensional domain. The inhibitors in this model have distinct diffusion rates and temporal expression patterns. These unique aspects of the model reflect recent experimental findings regarding the molecular interactions that regulate patterning in Anabaena. Output from the model is in good agreement with both the temporal and spatial characteristics of the pattern maintenance process observed experimentally

Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase transition point

Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase-transition point are analytically studied. A nonlinear Klein-Gordon equation is derived for the envelope of these wave packets. A variety of novel phenomena known to exist in this envelope equation are shown to also exist in the full equation including wave blowup, periodic bound states and solitary wave solutions.Comment: 4 pages, 2 figure