Game prototype for understanding safety issues of life boat launching process.

Novel advanced game techniques provide us with new possibilities to mimic a complicated training process, with the benefit of safety enhancement. In this paper, we design and implement a 3D game which imitates the lifeboat launching process. Lifeboat launching is such a complex but vital process which can on one side saving people's life on sea and on the other side associating many potential hazards. It involves both the tractor manoeuvres and boat operations. The primary objective of the game is to allow novices to better understand the sequence of the operations in launching process and manager the potential hazards happening during the launching. There is also great educational significance with the promotion of the game to the general public for enhanced awareness of safety issues. The key modules of the game are designed based on physical simulation which gives the players enhanced plausible cognition and enjoyable interaction

Topological Defects, Orientational Order, and Depinning of the Electron Solid in a Random Potential

We report on the results of molecular dynamics simulation (MD) studies of the classical two-dimensional electron crystal in the presence disorder. Our study is motivated by recent experiments on this system in modulation doped semiconductor systems in very strong magnetic fields, where the magnetic length is much smaller than the average interelectron spacing $a_0$, as well as by recent studies of electrons on the surface of helium. We investigate the low temperature state of this system using a simulated annealing method. We find that the low temperature state of the system always has isolated dislocations, even at the weakest disorder levels investigated. We also find evidence for a transition from a hexatic glass to an isotropic glass as the disorder is increased. The former is characterized by quasi-long range orientational order, and the absence of disclination defects in the low temperature state, and the latter by short range orientational order and the presence of these defects. The threshold electric field is also studied as a function of the disorder strength, and is shown to have a characteristic signature of the transition. Finally, the qualitative behavior of the electron flow in the depinned state is shown to change continuously from an elastic flow to a channel-like, plastic flow as the disorder strength is increased.Comment: 31 pages, RevTex 3.0, 15 figures upon request, accepted for publication in Phys. Rev. B., HAF94MD

How to Engineer Organic Solvent Resistant Enzymes: Insights from Combined Molecular Dynamics and Directed Evolution Study

Expanding synthetic capabilities to routinely employ enzymes in organic solvents (OSs) is a dream for protein engineers and synthetic chemists. Despite significant advances in the field of protein engineering, general and transferable design principles to improve the OS resistance of enzymes are poorly understood. Herein, we report a combined computational and directed evolution study of Bacillus subtlis lipase A (BSLA) in three OSs (i. e., 1,4-dioxane, dimethyl sulfoxide, 2,2,2-trifluoroethanol) to devise a rational strategy to guide engineering OS resistant enzymes. Molecular dynamics simulations showed that OSs reduce BSLA activity and resistance in OSs by (i) stripping off essential water molecules from the BLSA surface mainly through H-bonds binding; and (ii) penetrating the substrate binding cleft leading to inhibition and conformational change. Interestingly, integration of computational results with “BSLA-SSM” variant library (3439 variants; all natural diversity with amino acid exchange) revealed two complementary rational design strategies: (i) surface charge engineering, and (ii) substrate binding cleft engineering. These strategies are most likely applicable to stabilize other lipases and enzymes and assist experimentalists to design organic solvent resistant enzymes with reduced time and screening effort in lab experiments. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGa

Collective motions in globally coupled tent maps with stochastic updating

We study a generalization of globally coupled maps, where the elements are updated with probability $p$. When $p$ is below a threshold $p_c$, the collective motion vanishes and the system is the stationary state in the large size limit. We present the linear stability analysis.Comment: 6 pages including 5 figure

Electronic structure of fluorides: general trends for ground and excited state properties

The electronic structure of fluorite crystals are studied by means of density functional theory within the local density approximation for the exchange correlation energy. The ground-state electronic properties, which have been calculated for the cubic structures $CaF_{2}$,$SrF_{2}$, $BaF_{2}$, $CdF_{2}$, $HgF_{2}$, $\beta$-$PbF_{2}$, using a plane waves expansion of the wave functions, show good comparison with existing experimental data and previous theoretical results. The electronic density of states at the gap region for all the compounds and their energy-band structure have been calculated and compared with the existing data in the literature. General trends for the ground-state parameters, the electronic energy-bands and transition energies for all the fluorides considered are given and discussed in details. Moreover, for the first time results for $HgF_{2}$ have been presented

Stable and Metastable Structures of Cobalt on Cu(001): An ab initio Study

We report results of density-functional theory calculations on the structural, magnetic, and electronic properties of (1x1)-structures of Co on Cu(001) for coverages up to two monolayers. In particular we discuss the tendency towards phase separation in Co islands and the possibility of segregation of Cu on top of the Co-film. A sandwich structure consisting of a bilayer Co-film covered by 1ML of Cu is found to be the lowest-energy configuration. We also discuss a bilayer c(2x2)-alloy which may form due to kinetic reasons, or be stabilized at strained surface regions. Furthermore, we study the influence of magnetism on the various structures and, e.g., find that Co adlayers induce a weak spin-density wave in the copper substrate.Comment: 11 pages including 4 figures. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Small-polaron hopping conductivity in bilayer manganite La1.2_{1.2}Sr1.8_{1.8}Mn2_{2}O7_{7}

We report anisotropic resistivity measurements on a La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystal over a temperature $T$ range from 2 to 400 K and in magnetic fields $H$ up to 14 T. For $T\geq 218$ K, the temperature dependence of the zero-field in-plane $\rho_{ab}(T)$ resistivity obeys the adiabatic small polaron hopping mechanism, while the out-of-plane $\rho_{c}(T)$ resistivity can be ascribed by an Arrhenius law with the same activation energy. Considering the magnetic character of the polarons and the close correlation between the resistivity and magnetization, we developed a model which allows the determination of $\rho_{ab,c}(H,T)$. The excellent agreement of the calculations with the measurements indicates that small polarons play an essential role in the electrical transport properties in the paramagnetic phase of bilayer manganites.Comment: 4 pages, 3 figures, to appear in Physical Review

Water stress in maize production in the drylands of the Loess Plateau

Water stress during two maize (Zea mays L.) growing seasons (2013 and 2014) was investigated in a semiarid region of northwest China. The HYDRUS-1D model gave good simulation of the soil water content in different layers throughout a 0- to 200-cm depth during the maize growing season, with R-2 values of 70.6 and 77.0% for the calibration and validation periods, respectively. Water stress for maize production was observed in June of 2013 and in July of 2014. The soil water storage (SWS) decreased significantly during the early stage of the maize growing season, especially in 2014. The root depth and crop height were 20 cm deeper and 100 cm higher, respectively, in 2014 than in 2013 at the early stage. These results suggest that in the early stage of the maize growing season, pre-seeding SWS can alleviate crop water stress effectively via deep roots. Model simulation showed that the plow pan layer (at a depth of 20-40 cm), with high soil bulk density and a lower soil water retention curve, significantly reduced infiltration. High evapotranspiration and low precipitation result in a temporary dry layer during the early stage, highlighting the plow pan as the sensitive layer for water stress during the drought period. Effective management practices such as deep plowing, plastic film mulching, or water conservation treatments in the fallow period are needed to avoid the formation of this temporary dry layer during the drought period at the early stage and thus improve maize production in rainfed agriculture on the Loess Plateau of China