8,394 research outputs found

    T-equivariant disc potentials for toric Calabi-Yau manifolds

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    We formulate and compute the equivariant disc potentials of immersed SYZ fibers in toric Calabi-Yau manifolds, which are closely related to the open Gromov-Witten invariants of Aganagic-Vafa branes. The main tool is an equivariant version of the gluing method in \cite{CHL-glue,HKL}.First author draf

    Current rectification by asymmetric molecules: An ab initio study

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    We study current rectification effect in an asymmetric molecule HOOC-C6_6H4_4-(CH2_2)n_n sandwiched between two Aluminum electrodes using an {\sl ab initio} nonequilibrium Green function method. The conductance of the system decreases exponentially with the increasing number nn of CH2_2. The phenomenon of current rectification is observed such that a very small current appears at negative bias and a sharp negative differential resistance at a critical positive bias when n≥2n\ge 2. The rectification effect arises from the asymmetric structure of the molecule and the molecule-electrode couplings. A significant rectification ratio of ∼\sim38 can be achieved when n=5n=5.Comment: to appear in J. Chem. Phy

    Coupled ocean-atmosphere dynamics of the 2017 extreme coastal El Niño.

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    In March 2017, sea surface temperatures off Peru rose above 28 °C, causing torrential rains that affected the lives of millions of people. This coastal warming is highly unusual in that it took place with a weak La Niña state. Observations and ocean model experiments show that the downwelling Kelvin waves caused by strong westerly wind events over the equatorial Pacific, together with anomalous northerly coastal winds, are important. Atmospheric model experiments further show the anomalous coastal winds are forced by the coastal warming. Taken together, these results indicate a positive feedback off Peru between the coastal warming, atmospheric deep convection, and the coastal winds. These coupled processes provide predictability. Indeed, initialized on as early as 1 February 2017, seasonal prediction models captured the extreme rainfall event. Climate model projections indicate that the frequency of extreme coastal El Niño will increase under global warming

    Supramolecular assembly of cucurbit[6]uril and N-butyl-4-pyrrolidinopyridine

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    The nature of the supramolecular host-guest complex involving 4-pyrrolidinopyridine (BuPC4) and cucurbit[6]uril (Q[6]) has been investigated by NMR and UV spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography and isothermal titration calorimetry (ITC). The results revealed that the alkyl chain of the guest BuPC4 is located inside the cavity of the Q[6] host, whereas the other section of the BuPC4 guest remains outside of the portal

    Effects of relative orientation of the molecules on electron transport in molecular devices

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    Effects of relative orientation of the molecules on electron transport in molecular devices are studied by non-equilibrium Green's function method based on density functional theory. In particular, two molecular devices, with the planer Au7_{7} and Ag3_{3} clusters sandwiched between the Al(100) electrodes are studied. In each device, two typical configurations with the clusters parallel and vertical to the electrodes are considered. It is found that the relative orientation affects the transport properties of these two devices completely differently. In the Al(100)-Au7_7-Al(100) device, the conductance and the current of the parallel configuration are much larger than those in the vertical configuration, while in the Al(100)-Ag3_{3}-Al(100) device, an opposite conclusion is obtained

    Enhancing the hydrolysis of excess sludge using thermophilic Bacillus sp. Hnu under different oxygen supply conditions

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    A thermophilic Bacillus strain was isolated from excess sludge in the present study. The 16S rDNA analysis indicated that this strain was a Bacillus sp. and has not been reported previously (named Bacillus sp. Hnu). The aim of this paper was to investigate the enhanced efficiency of excess sludge hydrolysis by the addition of thermophilic Bacillus sp. Hnu under different oxygen supply conditions. The results indicated that higher temperature and more oxygen supply was advantageous to the volatile suspended solid removal ratio with the same effect to that of protease activity. The maximum volatile suspended solid removal ratio was achieved at 21.5 %, 42.5 %, and 54.4 % after 108 h digestion at pH 6.9 and 60°C and increased by 17.2 %, 38 %, and 45.4 % under anaerobic, microaerobic, and aerobic conditions compared with the control test, respectively. The hydrolysis rate constants for the anaerobic, microaerobic, and aerobic conditions were 3, 4.8, and 7 times (40°C) and 3.5, 9.8, and 11.8 times (50°C) and 2.7, 7.2, and 10.3 times (60°C). Hydrolysis performance indicated that the Bacillus sp. Hnu could accelerate the hydrolysis rate. The kinetic study showed that the hydrolysis of sludge with Bacillus sp. Hnu and the control test followed the first-order kinetics except at 60°C

    Primary Research on Bionic Design of Multi-surface Solar Concentrator Based on the Flower Structure

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    Plant can’t grow and reproduce without sunshine. Flowers have an inseparable relationship with sunshine as an important part of the plants. Most studies on the relationship of the plant and sunshine focus on the influence that sunshine reacts to plant, such as photosynthesis. However, there is no much more special attention on the relationship between flower structure and sunshine. Through the observation and comparison, the outlines of many flowers contour have some similarities with the solar concentrator. This paper delves into the relation between flower structure and light, in order to get the new ideas of designing solar concentrator.By means of extracting a contour line of flowers, their geometric structure models are got. Through simulation calculations of optical software, light-gathering performance of flowers is researched in the circumstance of different angle incident. Then based on researching the light-gathering process of the flowers, the innovative design ideas of bionics solar concentrators with excellent performance are presented. So in this way traditional thinking mode of single curve or surface used in solar concentrator design is expanded.Key words: flowers; bionic; solar concentrato
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