4,295 research outputs found

    Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

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    We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell

    KMT-2016-BLG-2052L: Microlensing Binary Composed of M Dwarfs Revealed from a Very Long Time-scale Event

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    We present the analysis of a binary microlensing event KMT-2016-BLG-2052, for which the lensing-induced brightening of the source star lasted for 2 seasons. We determine the lens mass from the combined measurements of the microlens parallax \pie and angular Einstein radius \thetae. The measured mass indicates that the lens is a binary composed of M dwarfs with masses of M1∼0.34 M⊙M_1\sim 0.34~M_\odot and M2∼0.17 M⊙M_2\sim 0.17~M_\odot. The measured relative lens-source proper motion of μ∼3.9 mas yr−1\mu\sim 3.9~{\rm mas}~{\rm yr}^{-1} is smaller than ∼5 mas yr−1\sim 5~{\rm mas}~{\rm yr}^{-1} of typical Galactic lensing events, while the estimated angular Einstein radius of \thetae\sim 1.2~{\rm mas} is substantially greater than the typical value of ∼0.5 mas\sim 0.5~{\rm mas}. Therefore, it turns out that the long time scale of the event is caused by the combination of the slow μ\mu and large \thetae rather than the heavy mass of the lens. From the simulation of Galactic lensing events with very long time scales (tE≳100t_{\rm E}\gtrsim 100 days), we find that the probabilities that long time-scale events are produced by lenses with masses ≥1.0 M⊙\geq 1.0~M_\odot and ≥3.0 M⊙\geq 3.0~M_\odot are ∼19%\sim 19\% and 2.6\%, respectively, indicating that events produced by heavy lenses comprise a minor fraction of long time-scale events. The results indicate that it is essential to determine lens masses by measuring both \pie and \thetae in order to firmly identify heavy stellar remnants such as neutron stars and black holes.Comment: 9 pages, 11 figure

    Phase diagram of a Disordered Boson Hubbard Model in Two Dimensions

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    We study the zero-temperature phase transition of a two-dimensional disordered boson Hubbard model. The phase diagram of this model is constructed in terms of the disorder strength and the chemical potential. Via quantum Monte Carlo simulations, we find a multicritical line separating the weak-disorder regime, where a random potential is irrelevant, from the strong-disorder regime. In the weak-disorder regime, the Mott-insulator-to-superfluid transition occurs, while, in the strong-disorder regime, the Bose-glass-to-superfluid transition occurs. On the multicritical line, the insulator-to-superfluid transition has the dynamical critical exponent z=1.35±0.05z=1.35 \pm 0.05 and the correlation length critical exponent ν=0.67±0.03\nu=0.67 \pm 0.03, that are different from the values for the transitions off the line. We suggest that the proliferation of the particle-hole pairs screens out the weak disorder effects.Comment: 4 pages, 4 figures, to be published in PR

    Regional distribution and properties of [3H]MK-801 binding sites determined by quantitative autoradiography in rat brain

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    [3H]MK-801 binding in rat brain was characterized using a quantitative autoradiographic binding assay. [3H]MK-801 binding (5 nM) reached equilibrium by 120 min at 23[deg]C. [3H]MK-801 appeared to label a single high affinity site with an affinity constant of approximately 11 nM. [3H]MK-801 binding was heterogeneously distributed throughout the brain with the following order of binding densities: hippocampal formation > cortical areas > striatum > thalamus.Competitive antagonists, -2-amino-5-phosphonopentanoic acid, -2-amino-7-phosphonoheptanoic acid, 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid, and cis-4-phosphonomethyl-2-piperidine carboxylic acid, inhibited [3H]MK-801 binding. Glycine antagonists, 7-chlorokynurenic acid and kynurenic acid, also inhibited [3H]MK-801 binding. Furthermore, the inhibition of [3H]MK-801 binding by the quinoxalinedione compounds 6-cyano-7-nitroquinoxaline-2,3-dione and 6,7-dinitroquinoxaline-2, 3-dione was reversed by glycine. [3H]MK-801 binding was also inhibited by zinc ions. [3H]MK-801 binding was enhanced by glycine or .These results demonstrate that [3H]MK-801 can be used in a quantitative autoradiographic assay as a functional probe for the receptor complex.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29627/1/0000716.pd
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