Complex network analysis of volatility spillovers between global financial indicators and G20 stock markets.

This paper analyses the dynamic transmission mechanism of volatility spillovers between key global financial indicators and G20 stock markets. To examine volatility spillover relations, we combine a bivariate GARCH-BEKK model with complex network theory. Specifically, we construct a volatility network of international financial markets utilising the spatial connectedness of spillovers (consisting of nodes and edges). The findings show that spillover relations between global variables and G20 markets vary significantly across five identified sub-periods. Notably, networks are much denser in crisis periods compared to non-crisis periods. In comparing two crisis periods, Global Financial Crisis (2008) and COVID-19 Crisis (2020) periods, the network statistics suggest that volatility spillovers in the latter period are more transitive and intense than the former. This suggests that financial volatility spreads more rapidly and directly through key financial indicators to the G20 stock markets. For example, oil and bonds are the largest volatility senders, while the markets of Saudi Arabia, Russia, South Africa, and Brazil are the main volatility receivers. In the former crisis, the source of financial volatility concentrates primarily in the USA, Australia, Canada, and Saudi Arabia, which are the largest volatility senders and receivers. China emerges as generally the least sensitive market to external volatility.

Factors Affecting Dental Students' Comfort with Online Synchronous Learning.

Background: The COVID-19 pandemic caused many universities to expand their use of videoconferencing technology to continue academic coursework. This study examines dental students' experience, comfort levels, and preferences with videoconferencing. Methods: Of 100 s-year US dental students enrolled in a local anesthesia course, 54 completed a survey following an online synchronous lecture given in August 2020. Survey questions asked about prior experience with videoconferencing, comfort levels with online and traditional classes, and reasons for not turning on their video (showing their face). Results: Overall, 48.2% had little or no experience with videoconferencing prior to March 2020. Students were more comfortable with in-classroom parameters (listening, asking questions, answering questions, and interacting in small groups (breakouts)) than with online synchronous learning, although differences were not significant (p's > 0.10). Regression analyses showed there were significant positive associations between videoconferencing experience and comfort with both answering questions and interacting in breakouts (B = 0.55, p = 0.04 and B = 0.54, p = 0.03, respectively). Students reported being more comfortable during in-classroom breakouts than in breakouts using videoconferencing (p = 0.003). Main reasons for students not turning on their cameras were that they did not want to dress up (48.1%), other students were not using their video features (46.3%), and they felt they did not look good (35.5%). Conclusions: Dental students were somewhat more comfortable with traditional in-person vs. online classroom parameters. Prior experience with videoconferencing was associated with increased comfort with synchronous learning, suggesting that after the pandemic, it may be beneficial to structure dental school curricula as a hybrid learning experience with both in-person and online synchronous courses.

Hierarchically Patterned Noncovalent Functionalization of 2D Materials by Controlled Langmuir-Schaefer Conversion.

Noncovalent monolayer chemistries are often used to functionalize 2D materials. Nanoscopic ligand ordering has been widely demonstrated (e.g., lying-down lamellar phases of functional alkanes); however, combining this control with micro- and macroscopic patterning for practical applications remains a significant challenge. A few reports have demonstrated that standing phase Langmuir films on water can be converted into nanoscopic lying-down molecular domains on 2D substrates (e.g., graphite), using horizontal dipping (Langmuir-Schaefer, LS, transfer). Molecular patterns are known to form at scales up to millimeters in Langmuir films, suggesting the possibility of transforming such structures into functional patterns on 2D materials. However, to our knowledge, this approach has not been investigated, and the rules governing LS conversion are not well understood. In part, this is because the conversion process is mechanistically very different from classic LS transfer of standing phases; challenges also arise due to the need to characterize structure in noncovalently adsorbed ligand layers <0.5 nm thick, at scales ranging from millimeters to nanometers. Here, we show that scanning electron microscopy enables diynoic acid lying-down phases to be imaged across this range of scales; using this structural information, we establish conditions for LS conversion to create hierarchical microscopic and nanoscopic functional patterns. Such control opens the door to tailoring noncovalent surface chemistry of 2D materials to pattern local interactions with the environment.

Multimicrometer Noncovalent Monolayer Domains on Layered Materials through Thermally Controlled Langmuir-Schaefer Conversion for Noncovalent 2D Functionalization.

As functionalized 2D materials are incorporated into hybrid materials, ensuring large-area structural control in noncovalently adsorbed films becomes increasingly important. Noncovalent functionalization avoids disrupting electronic structure in 2D materials; however, relatively weak molecular interactions in such monolayers typically reduce stability toward solution processing and other common material handling conditions. Here, we find that controlling substrate temperature during Langmuir-Schaefer conversion of a standing phase monolayer of diynoic amphiphiles on water to a horizontally oriented monolayer on a 2D substrate routinely produces multimicrometer domains, at least an order of magnitude larger than those typically achieved through drop-casting. Following polymerization, these highly ordered monolayers retain their structures during vigorous washing with solvents including water, ethanol, tetrahydrofuran, and toluene. These findings point to a convenient and broadly applicable strategy for noncovalent functionalization of 2D materials in applications that require large-area structural control, for instance, to minimize desorption at defects during subsequent solution processing.