Tuning Strain in Flexible Graphene Nanoelectromechanical Resonators

The structural flexibility of low dimensional nanomaterials offers unique opportunities for studying the impact of strain on their physical properties and for developing innovative devices utilizing strain engineering. A key towards such goals is a device platform which allows the independent tuning and reliable calibration of the strain. Here we report the fabrication and characterization of graphene nanoelectromechanical resonators(GNEMRs) on flexible substrates. Combining substrate bending and electrostatic gating, we achieve the independent tuning of the strain and sagging in graphene and explore the nonlinear dynamics over a wide parameter space. Analytical and numerical studies of a continuum mechanics model, including the competing higher order nonlinear terms, reveal a comprehensive nonlinear dynamics phase diagram, which quantitatively explains the complex behaviors of GNEMRs

Developmental differences in the structure of executive function in middle childhood and adolescence

Although it has been argued that the structure of executive function (EF) may change developmentally, there is little empirical research to examine this view in middle childhood and adolescence. The main objective of this study was to examine developmental changes in the component structure of EF in a large sample (N = 457) of 7–15 year olds. Participants completed batteries of tasks that measured three components of EF: updating working memory (UWM), inhibition, and shifting. Confirmatory factor analysis (CFA) was used to test five alternative models in 7–9 year olds, 10–12 year olds, and 13–15 year olds. The results of CFA showed that a single-factor EF model best explained EF performance in 7–9-year-old and 10–12-year-old groups, namely unitary EF, though this single factor explained different amounts of variance at these two ages. In contrast, a three-factor model that included UWM, inhibition, and shifting best accounted for the data from 13–15 year olds, namely diverse EF. In sum, during middle childhood, putative measures of UWM, inhibition, and shifting may rely on similar underlying cognitive processes. Importantly, our findings suggest that developmental dissociations in these three EF components do not emerge until children transition into adolescence. These findings provided empirical evidence for the development of EF structure which progressed from unity to diversity during middle childhood and adolescence

Peiminine regulates the biological characteristics of colorectal cancer cells via P13K/Akt/mTOR and oxidative stress pathways

Purpose: To investigate the influence of peiminine on biological characteristics of colorectal cancer cells, and the underlying mechanism.Methods: Two groups of cultured human colorectal cancer HCT-116 cells were used: peiminine and control groups. Peiminine group cells were exposed to the drug at a final concentration of 100 μmol/L. The effect of peiminine on cell proliferation was determined with CCK-8 method, while its effect on apoptosis was determined with flow cytometric method. Cell migration was determined with scratch test. The effect of peiminine on the expressions of proteins associated with the P13K/Akt/mTOR pathway and Wnt/β-catenin pathway in HCT-116 cells was determined with Western blotting assay.Results: Cell proliferation was markedly reduced in the peiminine group, relative to control (p < 0.05). There was higher percentage cell apoptosis in peiminine-treated cells than in control. Moreover, cell migration potential was significantly lower in the peiminine-treated cells. There were significantly downregulated levels of p-P13K, p-Akt and p-mTOR expressions in peiminine group, relative to the corresponding control expressions (p < 0.05). However, there were significantly higher relative expression of Wnt in peiminine group than in control cells, but β-catenin level was reduced, relative to the corresponding control level (p < 0.05).Conclusion: These data indicate that peiminine suppresses the proliferative, apoptotic and migratory potential of colorectal carcinoma HCT-116 cells via regulation of P13K/Akt/mTOR and oxidative stress pathways

Metal Amidoboranes and Their Derivatives for Hydrogen Storage

As potential hydrogen storage mediums, ammonia borane and its derivatives have been paid an increasing attention owing to their higher hydrogen capacities and facile dehydrogenation properties under moderate conditions. In this chapter, we presented extensive studies on thermodynamic tailoring of dehydrogenation of metal amidoboranes, metal borohydride-ammonia borane complexes, and metal amidoborane ammoniates as well as their derivatives, with special focus on the syntheses, crystal structures, and dehydrogenation properties. Finally, future perspective was given toward the practical applications