Symmetry-dependent screening of surface plasmons in ultrathin supported films: The case of Al/Si(111)

A joint theoretical and experimental study of plasmon excitations for Al overlayers on Si(111) has been carried out. The presence of the substrate is found to drastically modify the hybridization and charge density response of the surface plasmons of the metal overlayers. The symmetric mode, which is polarized toward the Al/Si interface, is strongly damped in intensity and significantly redshifted in energy. However, the antisymmetric mode, which is polarized to the metal-vacuum interface, is essentially unaffected by the presence of the substrate. A low-energy acoustic plasmon mode is also found in a one monolayer Al film and is almost unaffected by the substrate. The calculated plasmon dispersions with substrate are in good agreement with experimental data measured by electron energy loss spectroscopy. Our results suggest that interaction and screening at the subnanometer scale are symmetry dependent, a conclusion that may have general implications in other thin films and related structures

Path Integral Treatment of Proton Transport Processes in BaZrO3

Nuclear quantum effects on proton transfer and reorientation in BaZrO3 is investigated theoretically using the ab initio path-integral molecular-dynamics simulation technique. The result demonstrates that adding quantum fluctuations has a large effect on, in particular, the transfer barrier. The corresponding rates and diffusion coefficient are evaluated using the path-centroid transition state theory. In contrast with what is found assuming classical mechanics for the nuclear motion, the reorientation step becomes rate limiting below 600 K

Heterologous expression of a Glyoxalase I gene from sugarcane confers tolerance to several environmental stresses in bacteria

Glyoxalase I belongs to the glyoxalase system that detoxifies methylglyoxal (MG), a cytotoxic by-product produced mainly from triose phosphates. The concentration of MG increases rapidly under stress conditions. In this study, a novel glyoxalase I gene, designated as SoGloI was identified from sugarcane. SoGloI had a size of 1,091 bp with one open reading frame (ORF) of 885 bp encoding a protein of 294 amino acids. SoGloI was predicted as a Ni2+-dependent GLOI protein with two typical glyoxalase domains at positions 28–149 and 159–283, respectively. SoGloI was cloned into an expression plasmid vector, and the Trx-His-S-tag SoGloI protein produced in Escherichia coli was about 51 kDa. The recombinant E. coli cells expressing SoGloI compared to the control grew faster and tolerated higher concentrations of NaCl, CuCl2, CdCl2, or ZnSO4. SoGloI ubiquitously expressed in various sugarcane tissues. The expression was up-regulated under the treatments of NaCl, CuCl2, CdCl2, ZnSO4 and abscisic acid (ABA), or under simulated biotic stress conditions upon exposure to salicylic acid (SA) and methyl jasmonate (MeJA). SoGloI activity steadily increased when sugarcane was subjected to NaCl, CuCl2, CdCl2, or ZnSO4 treatments. Sub-cellular observations indicated that the SoGloI protein was located in both cytosol and nucleus. These results suggest that the SoGloI gene may play an important role in sugarcane’s response to various biotic and abiotic stresses

Effect of layered water structures on the anomalous transport through nanoscale graphene channels

From IOP Publishing via Jisc Publications RouterHistory: oa-requested 2018-03-19, received 2018-03-19, rev-recd 2018-05-01, accepted 2018-05-04, ppub 2018-08, epub 2018-08-16, open-access 2018-08-16Publication status: PublishedFunder: National Natural Science Foundation of China; doi: https://doi.org/10.13039/501100001809; Grant(s): U1530401Funder: Ministry of Science and Technology of the People’s Republic of China; doi: https://doi.org/10.13039/501100002855; Grant(s): 2017YFA0303400Abstract: We analyse the enhanced flow rate of water through nano-fabricated graphene channels that has been recently observed experimentally. Using molecular dynamics simulations in channels of similar lateral dimensions as the experimental ones, our results reveal for the first time a relationship between water structure and the variation of flux in the rectangular graphene channels. The substantial enhancement in the flow rate compared to Poieseuille flow is due to the formation of layered 2D structures in the confined space, which persists up to a channel height of 2.38 nm, corresponding to six graphene layers. The structure of the water shows an intricate crystal of pentagonal and square tiles, which has not been observed before. Beyond six layers we find a sudden drop in flux due to the disordering of the water, which can be understood by classical flow dynamics

Electronic structure, linear, nonlinear optical susceptibilities and birefringence of CuInX2 (X = S, Se, Te) chalcopyrite-structure compounds

The electronic structure, linear and nonlinear optical properties have been calculated for CuInX2 (X=S, Se, Te) chalcopyrite-structure single crystals using the state-of-the-art full potential linear augmented plane wave (FP-LAPW) method. We present results for band structure, density of states, and imaginary part of the frequency-dependent linear and nonlinear optical susceptibilities. We find that these crystals are semiconductors with direct band gaps. We have calculated the birefringence of these crystals. The birefringence is negative for CuInS2 and CuInSe2 while it is positive for CuInTe2 in agreement with the experimental data. Calculations are reported for the frequency-dependent complex second-order non-linear optical susceptibilities . The intra-band and inter-band contributions to the second harmonic generation increase when we replace S by Se and decrease when we replace Se by Te. We find that smaller energy band gap compounds have larger values of in agreement with the experimental data and previous theoretical calculations.Comment: 17 pages, 6 figure