4,710 research outputs found
Performance of the Lester battery charger in electric vehicles
Tests are performed on an improved battery charger. The primary purpose of the testing is to develop test methodologies for battery charger evaluation. Tests are developed to characterize the charger in terms of its charge algorithm and to assess the effects of battery initial state of charge and temperature on charger and battery efficiency. Tests show this charger to be a considerable improvement in the state of the art for electric vehicle chargers
An Estimation of U.S. Industry-Level Capital-Labor Substitution
A key parameter that determines the distributional impacts of a policy shift in general equilibrium models is the elasticity of substitution between capital and labor. Despite the importance of this parameter in applied modeling, its identification continues to pose a challenge. Given the structure of most growth models, we posit that the true relationship between capital and labor is likely to be close to Cobb- Douglas. Using a rich new data set from the Bureau of Economic Analysis, we estimate substitution elasticities for 28 industries, which cover the entire economy, and provide an indication of the long- and short-run estimates. We fail to reject the Cobb-Douglas specification in 20 of the 28 industries. These findings lend support to the Cobb-Douglas specification as a transparent starting point in simulation analysis.Econometric Methods; Time Series Models; Computable General Equilibrium Models
Testing a double AGN hypothesis for Mrk 273
The ULIRG Mrk 273 contains two infrared nuclei, N and SW, separated by 1
arcsec. A Chandra observation has identified the SW nucleus as an absorbed
X-ray source with nH ~4e23 cm-2 but also hinted at the possible presence of a
Compton thick AGN in the N nucleus, where a black hole of 10^9 Msun is inferred
from the ionized gas kinematics. The intrinsic X-ray spectral slope recently
measured by NuSTAR is unusually hard (photon index of ~1.3) for a Seyfert
nucleus, for which we seek an alternative explanation. We hypothesise a
strongly absorbed X-ray source in N, of which X-ray emission rises steeply
above 10 keV, in addition to the known X-ray source in SW, and test it against
the NuSTAR data, assuming the standard spectral slope (photon index of 1.9).
This double X-ray source model gives a good explanation of the hard continuum
spectrum, the deep Fe K absorption edge, and the strong Fe K line observed in
this ULIRG, without invoking the unusual spectral slope required for a single
source interpretation. The putative X-ray source in N is found to be absorbed
by nH = 1.4(+0.7/-0.4)e24 cm-2. The estimated 2-10 keV luminosity of the N
source is 1.3e43 erg/s, about a factor of 2 larger than that of SW during the
NuSTAR observation. Uncorrelated variability above and below 10 keV between the
Suzaku and NuSTAR observations appears to support the double source
interpretation. Variability in spectral hardness and Fe K line flux between the
previous X-ray observations is also consistent with this picture.Comment: 6 pages, 5 figures, Accepted for publication in A&
Effect of spatial inhomogeneity on the mapping between strongly interacting fermions and weakly interacting spins
A combined analytical and numerical study is performed of the mapping between
strongly interacting fermions and weakly interacting spins, in the framework of
the Hubbard, t-J and Heisenberg models. While for spatially homogeneous models
in the thermodynamic limit the mapping is thoroughly understood, we here focus
on aspects that become relevant in spatially inhomogeneous situations, such as
the effect of boundaries, impurities, superlattices and interfaces. We consider
parameter regimes that are relevant for traditional applications of these
models, such as electrons in cuprates and manganites, and for more recent
applications to atoms in optical lattices. The rate of the mapping as a
function of the interaction strength is determined from the Bethe-Ansatz for
infinite systems and from numerical diagonalization for finite systems. We show
analytically that if translational symmetry is broken through the presence of
impurities, the mapping persists and is, in a certain sense, as local as
possible, provided the spin-spin interaction between two sites of the
Heisenberg model is calculated from the harmonic mean of the onsite Coulomb
interaction on adjacent sites of the Hubbard model. Numerical calculations
corroborate these findings also in interfaces and superlattices, where
analytical calculations are more complicated.Comment: 7 pages, 6 figure
Hyperadrenocorticism of calorie restriction contributes to its anti‐inflammatory action in mice
Shocked Gas in IRAS F17207-0014: ISM Collisions and Outflows
We combine optical and near-infrared AO-assisted integral field observations
of the merging ULIRG IRAS F17207-0014 from the Wide-Field Spectrograph (WiFeS)
and Keck/OSIRIS. The optical emission line ratios [N II]/H, [S
II]/H, and [O I]/H reveal a mixing sequence of shocks present
throughout the galaxy, with the strongest contributions coming from large radii
(up to 100% at 5 kpc in some directions), suggesting galactic-scale
winds. The near-infrared observations, which have approximately 30 times higher
spatial resolution, show that two sorts of shocks are present in the vicinity
of the merging nuclei: low-level shocks distributed throughout our
field-of-view evidenced by an H/Br line ratio of 0.6-4, and
strong collimated shocks with a high H/Br line ratio of
4-8, extending south from the two nuclear disks approximately 400 pc
(0.5 arcsec). Our data suggest that the diffuse shocks are caused by the
collision of the interstellar media associated with the two progenitor galaxies
and the strong shocks trace the base of a collimated outflow coming from the
nucleus of one of the two disks.Comment: accepted to MNRA
Optical investigation of thermoelectric topological crystalline insulator PbSnSe
PbSnSe is a novel alloy of two promising thermoelectric
materials PbSe and SnSe that exhibits a temperature dependent band inversion
below 300 K. Recent work has shown that this band inversion also coincides with
a trivial to nontrivial topological phase transition. To understand how the
properties critical to thermoelectric efficiency are affected by the band
inversion, we measured the broadband optical response of
PbSnSe as a function of temperature. We find clear optical
evidence of the band inversion at K, and use the extended Drude
model to accurately determine a dependence of the bulk carrier
lifetime, associated with electron-acoustic phonon scattering. Due to the high
bulk carrier doping level, no discriminating signatures of the topological
surface states are found, although their presence cannot be excluded from our
data.Comment: 11 pages, 6 figure
Co-targeting HGF/cMET Signaling with MEK Inhibitors in Metastatic Uveal Melanoma.
Patients with metastatic uveal melanoma usually die within 1 year of diagnosis, emphasizing an urgent need to develop new treatment strategies. The liver is the most common site of metastasis. Mitogen-activated protein kinase kinase (MEK) inhibitors improve survival in V600 BRAF-mutated cutaneous melanoma patients but have limited efficacy in patients with uveal melanoma. Our previous work showed that hepatocyte growth factor (HGF) signaling elicits resistance to MEK inhibitors in metastatic uveal melanoma. In this study, we demonstrate that expression of two BH3-only family proteins, Bim-EL and Bmf, contributes to HGF-mediated resistance to MEK inhibitors. Targeting HGF/cMET signaling with LY2875358, a neutralizing and internalizing anti-cMET bivalent antibody, and LY2801653, a dual cMET/RON inhibitor, overcomes resistance to trametinib provided by exogenous HGF and by conditioned medium from primary hepatic stellate cells. We further determined that activation of PI3Kα/γ/δ isoforms mediates the resistance to MEK inhibitors by HGF. Combination of LY2801653 with trametinib decreases AKT phosphorylation and promotes proapoptotic PARP cleavage in metastatic uveal melanoma explants. Together, our data support the notion that selectively blocking cMET signaling or PI3K isoforms in metastatic uveal melanoma may break the intrinsic resistance to MEK inhibitors provided by factors from stromal cells in the liver
Light trapping in ultrathin plasmonic solar cells
We report on the design, fabrication, and measurement of ultrathin film a-Si:H solar cells with nanostructured plasmonic back contacts, which demonstrate enhanced short circuit current densities compared to cells having flat or randomly textured back contacts. The primary photocurrent enhancement occurs in the spectral range from 550 nm to 800 nm. We use angle-resolved photocurrent spectroscopy to confirm that the enhanced absorption is due to coupling to guided modes supported by the cell. Full-field electromagnetic simulation of the absorption in the active a-Si:H layer agrees well with the experimental results. Furthermore, the nanopatterns were fabricated via an inexpensive, scalable, and precise nanopatterning method. These results should guide design of optimized, non-random nanostructured back reflectors for thin film solar cells
Magnetic Fields Boosted by Gluon Vortices in Color Superconductivity
We investigate the effects of an external magnetic field in the gluon
dynamics of a color superconductor with three massless quark flavors. In the
framework of gluon mean-field theory at asymptotic densities, we show that the
long-range component of the external magnetic field that
penetrates the CFL phase produces an instability when its strength becomes
larger than the Meissner mass of the charged gluons. As a consequence, the
magnetic field causes the formation of a vortex state characterized by the
condensation of charged gluons and the creation of magnetic flux tubes. Inside
the flux tubes the magnetic field is stronger than the applied one. This
antiscreening effect is connected to the anomalous magnetic moment of the gluon
field. We suggest how this same mechanism could serve to remove the
chromomagnetic instabilities existing in gapless color superconductivity.Comment: Version to appear in PRL. Typos corrected and several references
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