Size-dependent microwave heating and catalytic activity of fine iron particles in the deep dehydrogenation of hexadecane

Knowledge of the electromagnetic microwave radiation–solid matter interaction and ensuing mechanisms at active catalytic sites will enable a deeper understanding of microwave-initiated chemical interactions and processes, and will lead to further optimization of this class of heterogeneous catalysis. Here, we study the fundamental mechanism of the interaction between microwave radiation and solid Fe catalysts and the deep dehydrogenation of a model hydrocarbon, hexadecane. We find that the size-dependent electronic transition of particulate Fe metal from a microwave “reflector” to a microwave “absorber” lies at the heart of efficient metal catalysis in these heterogeneous processes. In this regard, the optimal particle size of a Fe metal catalyst for highly effective microwave-initiated dehydrogenation reactions is approximately 80–120 nm, and the catalytic performance is strongly dependent on the ratio of the mean radius of Fe particles to the microwave skin depth (r/δ) at the operating frequency. Importantly, the particle size of selected Fe catalysts will ultimately affect the basic heating properties of the catalysts and decisively influence their catalytic performance under microwave initiation. In addition, we have found that when two or more materials─present as a mechanical mixture─are simultaneously exposed to microwave irradiation, each constituent material will respond to the microwaves independently. Thus, the interaction between the two materials has been found to have synergistic effects, subsequently contributing to heating and improving the overall catalytic performance

Associations of latent patterns of parent‒child communication with communication quality and mental health outcomes among Chinese left-behind children

Abstract Background Parent‒child communication in migrant families is essential to family bonds and the mental health of left-behind children (LBC). Little is known about the different patterns of communication between migrant parents and LBC and associated communication quality and mental health outcomes. Methods A sample of 2,183 Chinese children (mean age = 12.95 ± 1.29 years) from Anhui province, including LBC whose parents had both migrated (n = 1,025) and children whose parents had never migrated (never-LBC, n = 1,158), was analyzed. With the LBC sample, latent class analysis was applied to identify the patterns of parent‒child communication. Multinomial logistic regression analysis was conducted to assess the associations between the sociodemographic variables and class membership of LBC. Analysis of covariance and chi-square tests were used to compare communication quality and mental health outcome differences among the classes of LBC and between each of the classes and never-LBC. Results Five latent classes of communication formed through different media or channels between migrant parents and their LBC were identified. Higher household economic status (OR = 2.81, p < 0.05) was associated with adequate communication. LBC in Class 1, defined by frequent technologically-mediated and face-to-face communication, had a significantly higher quality of communication with their migrant parents (F = 8.92, p < 0.001) and better mental health than those in other latent classes; these children did not have significantly worse mental health outcomes compared to never -LBC. Conclusions Facilitating multichannel parent‒child communication is a practical way of reducing mental health inequities between LBC and their peers