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A chemical dynamics simulation was performed to study collisions between neon (Ne) atoms and a liquid squalane (2,6,10,15,19,23-hexamethyltetracosane) surface. Ten thousand trajectories were calculated, with an incident energy of 10 kcal/mol, incident polar angle 45° with respect to the surface normal, and random azimuthal angle. The final energy distribution, angular distribution, and impact sites were determined and analyzed. The incident Ne atoms have short residence times on the surface with most atoms successfully scattering within 3−7 ps. Due to thermal fluctuations of the surface, the incident energy is dissipated efficiently, and more than 60% of the initial energy of the Ne atoms is transferred with three or more “kicks” on the surface. For in-plane scattered Ne atoms with a final polar angle of 45°, the energy transfer is 58% ± 8%, which is in good agreement with the experimental value of 60% (J. Chem. Phys. 1993 , 99, 7056). A bimodal energy distribution is observed for both in-plane and out-of-plane scattering, with a much larger Boltzmann component for out-of-plane scattering as compared to in-plane scattering. The incident Ne atoms are found to primarily impinge the terminal methyl groups of the squalane molecules, and such impact probability is correlated with the interfacial structure of the squalane surface. Comparison with previous study of Ne atom scattering off a H-terminated alkyl thiol self-assembled monolayer (H-SAM) surface shows that energy transfer to squalane is less efficient than to the H-SAM, because flexible intermolecular couplings of the alkyl thiol chains of the H-SAM provide efficient dissipation channels to accommodate the incident Ne atom’s energy.

A better understanding of biogeography of Glomeromycota is essential for the conservation of arbuscular mycorrhizal (AM) fungal species and the ecosystem services that they provide worldwide. We examined the spatial dynamics of AM fungi along two slopes (4149 m a.s.l. to the summit at 5033 m a.s.l.) of Mount Mila on the Tibetan Plateau. Our hypothesis was that AM fungal communities at higher elevation would show distinct assemblages with lower diversity in conditions of increasing environmental harshness. A total of 52 operational taxonomic units (OTUs) spanning all four orders were detected and some OTUs were habitat specific. Nearly 30% of the OTUs were new phylotypes, including two family-like clades. Distinct communities of AM fungi were found at the higher elevation, demonstrating potential niche differentiation along the elevation gradient. Elevation patterns of taxon richness/diversity differed between the two transects, decreasing with increasing elevation on the eastern slope and being unimodal (or lacking a pattern) on the western slope. Taken together, our findings provide evidence of a significant spatial structure of AM fungi across the elevation gradient, with the distribution patterns of these fungi regulated simultaneously by the plant communities, soil properties and climatic conditions in this plateau montane ecosystem.

Because of the rapid development of urbanization and industrialization and rise of economy, China has frequently experienced haze pollution. These haze pollution events profoundly affect human health, such as

PurposeAlthough blood banks have recently started to recruit blood donors through social media platforms, including WeChat, to increase recruitment effectiveness, few researchers have studied their effects on blood donation behavior. The aim of this study is to examine the influence of using official WeChat accounts on repeat blood donation behavior.Design/methodology/approachThis paper used the backstage operation data of official WeChat accounts and blood supply chain management system data from the blood bank for the study to analyze the changes in repeat blood donation behavior. First, to analyze the changes in the average frequency of blood donation per year, average volume of single blood donation and blood eligible rate of repeat blood donors before and after following the official WeChat accounts by difference-in-differences model combined with propensity score matching (PSM-DID). Second, we examined the impact of official WeChat accounts on the proportion of repeat blood donors through survival analysis.FindingsThe results show that following WeChat accounts increases the average frequency of blood donation and blood eligible rate of repeat blood donors by 14.36% and 1.19%, respectively, and have no significant effect on the average volume of single blood donation. Further, WeChat accounts have a more significant impact on the average frequency of blood donations per year for workers, farmers, medical staff and groups with education levels of junior high school. In addition, official WeChat accounts can effectively increase the proportion of repeat donors.Originality/valueThe results provide a quantitative basis for the influence of official WeChat accounts on repeat blood donation behaviors. On the one hand, it is of great significance to guide the publicity and recruitment of unpaid blood banks. On the other hand, it provides an evidence for the promotion of official WeChat accounts.

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We present a critical theoretical study of electronic properties of silicon nanoclusters, in particular the roles played by symmetry, relaxation, and hydrogen passivation on the the stability, the gap states and the energy gap of the system using the order-N [O(N)] non-orthogonal tight-binding molecular dynamics and the local analysis of electronic structure. We find that for an unrelaxed cluster with its atoms occupying the regular tetrahedral network, the presence of undistorted local bonding configuration is sufficient for the appearance of a small clean energy gap. However, the energy gap of the unrelaxed cluster does not start at the highest occupied molecular orbital (HOMO). In fact, between the HOMO and the lower-edge of the energy gap, localized dangling bond states are found. With hydrogen passivation, the localized dangling bond states are eliminated, resulting in a wider and clean energy gap. Relaxation of these hydrogen passivated clusters does not alter either the structure or the energy gap appreciably. However, if the silicon clusters are allowed to relax first, the majority of the dangling bonds are eliminated but additional defect states due to bond distortion appear, making the energy gap dirty. Hydrogen passivation of these relaxed clusters will further eliminate most of the remnant dangling bonds but no appreciable effect on the defect states associated with bond distortions, thus still resulting in a dirty gap. For the hydrogen-passivated Si N nanoclusters with no bond distortion and no overall symmetry, we have studied the variation of the energy gap as a function of size of the cluster for N in the range of 80 < N < 6000. The dependence of the energy gap on the size shows a similar behavior as that for silicon nanoclusters with no bond distortion but possessing overall symmetry. PACS: 71.24.+q, 71.15.Fv

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