675 research outputs found
Optically-Nonactive Assorted Helices Array with Interchangeable Magnetic/Electric Resonance
We report here the designing of optically-nonactive metamaterial by
assembling metallic helices with different chirality. With linearly polarized
incident light, pure electric or magnetic resonance can be selectively
realized, which leads to negative permittivity or negative permeability
accordingly. Further, we show that pure electric or magnetic resonance can be
interchanged at the same frequency band by merely changing the polarization of
incident light for 90 degrees. This design demonstrates a unique approach to
construct metamaterial.Comment: 15 pages, 4 figure
catena-Poly[silver(I)-μ-acridine-9-carboxylÂato-κ3 N:O,O′]
In the title coordination polymer, [Ag(C14H8NO2)]n, the AgI cation is coordinated by two O atoms and one N atom from two symmetry-related acridine-9-carboxylÂate ligands in a distorted trigonal-planar geometry. The metal atoms are connected by the ligands to form chains running parallel to the b axis. π–π stacking interÂactions [centroid-to-centroid distances 3.757 (2)–3.820 (2) Å] and weak Ag⋯O interÂactions further link the chains to form a layer network parallel to the ab plane. The AgI cation is disordered over two positions, with refined site-occupancy factors of 0.73 (3):0.27 (3)
Submillimeter Array Observations of the Molecular Outflow in High-mass Star-forming Region G240.31+0.07
We present Submillimeter Array observations toward the 10^{4.7} Lsun
star-forming region G240.31+0.07, in the J=2-1 transition of 12CO and 13CO and
at 1.3 mm continuum, as well as the 12CO and 13CO observations from the Caltech
Submillimeter Observatory to recover the extended emission filtered out by the
interferometer. Maps of the 12CO and 13CO emission show a bipolar, wide-angle,
quasi-parabolic molecular outflow, roughly coincident with an IR nebula
revealed by the Spitzer 3.6 and 4.5 micron emission. The outflow has ~98 Msun
molecular gas, making it one of the most massive molecular outflows known, and
resulting in a very high mass-loss rate of 4.1 by 10^{-3} Msun yr^{-1} over a
dynamical timescale of 2.4 by 10^4 yr. The 1.3 mm continuum observations with a
4" by 3" beam reveal a flattened dusty envelope of ~150 Msun, which is further
resolved with a 1.2" by 1" beam into three dense cores with a total mass of ~40
Msun. The central mm core, showing evidence of active star formation,
approximately coincides with the geometric center of the bipolar outflow thus
most likely harbors the powering source of the outflow. Overall our
observations provide the best case to date of a well-defined wide-angle
molecular outflow in a >10^4 Lsun star-forming region. The outflow is
morphologically and kinematically similar to low-mass protostellar outflows but
has two to three orders of magnitude greater mass, momentum, and energy, and is
apparently driven by an underlying wide-angle wind, hence further supports that
high-mass stars up to late-O types, even in a crowded clustering environment,
can form as a scaled-up version of low-mass star formation.Comment: accepted for publication in the Ap
The Promotion of the Efficiency of Organic Photovoltaic Devices by Addition of Anisotropic CdSe Nanocrystals
CdSe nanocrystals (NCs) with different morphologies have been synthesized and applied as the acceptor in the active layer of the organic photovoltaic (OPV) devices. CdSe tetrapod (TP)/nanorod (NR) with zinc-blended seeds and wurtzite arms is prepared by seed growth method and mixed with poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). When the concentrations of CdSe in P3HT: PCBM system are 50 wt% optimally, the efficiency can be promoted about 4.3%, suggesting that an enhancement of 13.2% can be obtained and the addition of anisotropic CdSe NCs content in the active layer can be beneficial for the transport of electrons and light absorption in the OPV devices
Vertically-aligned graphene nanowalls grown via plasma-enhanced chemical vapor deposition as a binder-free cathode in Li-O_2 batteries
In the present report, vertically-aligned graphene nanowalls are grown on Ni foam (VA-G/NF) using plasma-enhanced chemical vapor deposition method at room temperature. Optimization of the growth conditions provides graphene sheets with controlled defect sites. The unique architecture of the vertically-aligned graphene sheets allows sufficient space for the ionic movement within the sheets and hence enhancing the catalytic activity. Further modification with ruthenium nanoparticles (Ru NPs) drop-casted on VA-G/NF improves the charge overpotential for lithium–oxygen (Li–O_2) battery cycles. Such reduction we believe is due to the easier passage of ions between the perpendicularly standing graphene sheets thereby providing ionic channels
Vertically-aligned graphene nanowalls grown via plasma-enhanced chemical vapor deposition as a binder-free cathode in Li-O_2 batteries
In the present report, vertically-aligned graphene nanowalls are grown on Ni foam (VA-G/NF) using plasma-enhanced chemical vapor deposition method at room temperature. Optimization of the growth conditions provides graphene sheets with controlled defect sites. The unique architecture of the vertically-aligned graphene sheets allows sufficient space for the ionic movement within the sheets and hence enhancing the catalytic activity. Further modification with ruthenium nanoparticles (Ru NPs) drop-casted on VA-G/NF improves the charge overpotential for lithium–oxygen (Li–O_2) battery cycles. Such reduction we believe is due to the easier passage of ions between the perpendicularly standing graphene sheets thereby providing ionic channels
Impacts of air pollutants from rural Chinese households under the rapid residential energy transition
Rural residential energy consumption in China is experiencing a rapid transition towards clean energy, nevertheless, solid fuel combustion remains an important emission source. Here we quantitatively evaluate the contribution of rural residential emissions to PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm) and the impacts on health and climate. The clean energy transitions result in remarkable reductions in the contributions to ambient PM2.5, avoiding 130,000 (90,000-160,000) premature deaths associated with PM2.5 exposure. The climate forcing associated with this sector declines from 0.057 ± 0.016 W/m2 in 1992 to 0.031 ± 0.008 W/m2 in 2012. Despite this, the large remaining quantities of solid fuels still contributed 14 ± 10 μg/m3 to population-weighted PM2.5 in 2012, which comprises 21 ± 14% of the overall population-weighted PM2.5 from all sources. Rural residential emissions affect not only rural but urban air quality, and the impacts are highly seasonal and location dependent
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