1,855 research outputs found
Seasonal Variability In The Ionosphere Of Uranus
Infrared ground-based observations using IRTF, UKIRT, and Keck II of Uranus have been analyzed as to identify the long-term behavior of the H-3(+) ionosphere. Between 1992 and 2008 there are 11 individual observing runs, each recording emission from the H-3(+) Q branch emission around 4 mu m through the telluric L' atmospheric window. The column-averaged rotational H-3(+) temperature ranges between 715 K in 1992 and 534 K in 2008, with the linear fit to all the run-averaged temperatures decreasing by 8 K year(-1). The temperature follows the fractional illumination curve of the planet, declining from solstice (1985) to equinox (2007). Variations in H-3(+) column density do not appear to be correlated to either solar cycle phase or season. The radiative cooling by H-3(+) is similar to 10 times larger than the ultraviolet solar energy being injected to the atmosphere. Despite the fact that the solar flux alone is incapable of heating the atmosphere to the observed temperatures, the geometry with respect to the Sun remains an important driver in determining the thermospheric temperature. Therefore, the energy source that heats the thermosphere must be linked to solar mechanisms. We suggest that this may be in the form of conductivity created by solar ionization of atmospheric neutrals and/or seasonally dependent magnetospherically driven current systems.STFC PP/E/000983/1, ST/G0022223/1RCUKGemini ObservatoryNational Aeronautics and Space Administration (NASA) NXX08A043G, NNX08AE38AAstronom
Ambipolar charge injection and transport in a single pentacene monolayer island
Electrons and holes are locally injected in a single pentacene monolayer
island. The two-dimensional distribution and concentration of the injected
carriers are measured by electrical force microscopy. In crystalline monolayer
islands, both carriers are delocalized over the whole island. On disordered
monolayer, carriers stay localized at their injection point. These results
provide insight into the electronic properties, at the nanometer scale, of
organic monolayers governing performances of organic transistors and molecular
devices.Comment: To be published in Nano Letter
CARMA observations of massive Planck-discovered cluster candidates at z>0.5 associated with WISE overdensities: Breaking the size-flux degeneracy
We use a Bayesian software package to analyze CARMA-8 data towards 19
unconfirmed Planck SZ-cluster candidates from Rodriguez-Gonzalvez et al.
(2015), that are associated with significant overdensities in WISE. We used two
cluster parameterizations, one based on a (fixed shape) generalized-NFW
pressure profile and another based on a beta-gas-density profile (with varying
shape parameters) to obtain parameter estimates for the nine CARMA-8
SZ-detected clusters. We find our sample is comprised of massive,
Y_{500}=0.0010 \pm 0.0015 arcmin^2, relatively compact, theta_{500}= 3.9 \pm
2.0 arcmin systems. Results from the beta model show that our cluster
candidates exhibit a heterogeneous set of brightness-temperature profiles.
Comparison of Planck and CARMA-8 measurements showed good agreement in Y_{500}
and an absence of obvious biases. We estimated the total cluster mass M_{500}
as a function of z for one of the systems; at the preferred photometric
redshift of 0.5, the derived mass, M_{500} \approx 0.8 \pm 0.2 \times 10^{15}
Msun. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our
cluster candidates to be at z=0.565. Applying a Planck prior in Y_{500} to the
CARMA-8 results reduces uncertainties for both parameters by a factor >4,
relative to the independent Planck or CARMA-8 measurements. We here demonstrate
a powerful technique to find massive clusters at intermediate z \gtrsim 0.5
redshifts using a cross-correlation between Planck and WISE data, with
high-resolution follow-up with CARMA-8. We also use the combined capabilities
of Planck and CARMA-8 to obtain a dramatic reduction by a factor of several, in
parameter uncertainties.Comment: 26 pages, 8 figures, appearing in MNRAS (responded to referee report
Quantum interference due to crossed Andreev reflection in a d-wave superconductor with two nano-contacts
The crossed Andreev reflection in a hybrid nanostructure consisting of a
d-wave superconductor and two quantum wires is theoretically studied. When the
(110) oriented surface of the superconductor is in contact with the wires
parallel and placed close to each other, the Andreev bound state is formed by
the crossed Andreev reflection. The conductance has two resonance peaks well
below the gap structure in the case of tunnel contacts. These peaks originate
from the bonding and antibonding Andreev bound states of hole wave functions.Comment: 4 pages, 3 figure
Analisis Merkuri (Hg) dan Arsen (As) di Sedimen Sungai Ranoyapo Kecamatan Amurang Sulawesi Utara
Penelitian ini bertujuan untuk mengukur konsentrasi merkuri dan arsen di sedimen Sungai Ranoyapo. Pengukuran konsentrasi total merkuri menggunakan Cold Vapor-Atomic Absorption Spectrometry (CV-AAS) sedangkan pengukuran konsentrasi total arsen menggunakan Atomic Absorption Spectrometry (AAS). Hasil yang diperoleh menunjukkan konsentrasi total merkuri di sedimen sungai yang diambil dari Desa Lompad, Desa Picuan, Desa karimbow I, Desa Karimbow II dan muara Sungai Ranoyapo berturut-turut yaitu 0,05 ppm, 0,05 ppm, 1,3 ppm, 0,18 ppm dan 0,05 ppm. Konsentrasi total arsen di sedimen sungai yang diambil dari Desa Lompad, Desa Picuan, Desa Karimbow I, Desa Karimbow II dan muara Sungai Ranoyapo berturut-turut yaitu 3 ppm, 2 ppm, 100 ppm, 2 ppm dan 1 ppm. Konsentrasi total merkuri dan arsen tertinggi adalah di Desa Karimbow I yang merupakan daerah pertambangan emas rakyat
Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor
Surface characterizations of an organophosphorus (OP) gas detector based on
chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET)
were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and
correlated with changes in the current-voltage characteristics of the devices.
KPFM measurements on FETs allow (i) to investigate the contact potential
difference (CPD) distribution of the polarized device as function of the gate
voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis
associated to the presence of mobile ions on the surface. The CPD measured by
KPFM on the silicon nanoribbon was corrected due to side capacitance effects in
order to determine the real quantitative surface potential. Comparison with
macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out.
These two approaches were quantitatively consistent. An important increase of
the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor
grafting, corresponding to a decrease of the work function, and a weaker
variation after exposure to OP (between - 14 mV and - 61 mV) was measured.
Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The
OP molecules were essentially localized on the Si-NR confirming effectiveness
and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and
succeeded in the detection of low vapor concentrations (40 ppm).Comment: Paper and supporting information, J. Phys. Chem. C, 201
Circular economy strategies for electric vehicle batteries reduce raw material reliance
The wide adoption of lithium-ion batteries used in electric vehicles will require increased natural resources for the automotive industry. The expected rapid increase in batteries could result in new resource challenges and supply-chain risks. To strengthen the resilience and sustainability of automotive supply chains and reduce primary resource requirements, circular economy strategies are needed. Here we illustrate how these strategies can reduce the extraction of primary raw materials, that is, cobalt supplies. Material flow analysis is applied to understand current and future flows of cobalt embedded in electric vehicle batteries across the European Union. A reference scenario is presented and compared with four strategies: technology-driven substitution and technology-driven reduction of cobalt, new business models to stimulate battery reuse/recycling and policy-driven strategy to increase recycling. We find that new technologies provide the most promising strategies to reduce the reliance on cobalt substantially but could result in burden shifting such as an increase in nickel demand. To avoid the latter, technological developments should be combined with an efficient recycling system. We conclude that more-ambitious circular economy strategies, at both government and business levels, are urgently needed to address current and future resource challenges across the supply chain successfully
Connexin36 knockout mice display increased sensitivity to pentylenetetrazol-induced seizure-like behaviors
Large-scale synchronous firing of neurons during seizures is modulated by electrotonic coupling between neurons via gap junctions. To explore roles for connexin36 (Cx36) gap junctions in seizures, we examined the seizure threshold of connexin36 knockout (Cx36KO) mice using a pentylenetetrazol (PTZ) model
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