2,913 research outputs found
An Analysis of Latin American Foreign Investment Law: Proposals for Striking a Balance Between Foreign Investment and Political Stability
An Analysis of Latin American Foreign Investment Law: Proposals for Striking a Balance Between Foreign Investment and Political Stability
Implications of Shock Wave Experiments with Precompressed Materials for Giant Planet Interiors
This work uses density functional molecular dynamics simulations of fluid
helium at high pressure to examine how shock wave experiments with
precompressed samples can help characterizing the interior of giant planets. In
particular, we analyze how large of a precompression is needed to probe a
certain depth in a planet's gas envelope. We find that precompressions of up to
0.1, 1.0, 10, or 100 GPa are needed to characterized 2.5, 5.9, 18, to 63% of
Jupiter's envelope by mass.Comment: Submitted As Proceedings Article For The American Physical Society
Meeting On Shock Compression Of Condensed Matter, Hawaii, June, 200
Propagation of highly nonlinear signals in a two dimensional network of granular chains
We report the first experimental observation of highly nonlinear signals propagating in a two dimensional system composed of granular chains. In this system one of the chains contacts two others to allow splitting and redirecting the solitary-like signal formed in the first chain. The system consists of a double Y-shaped guide in which high- and low-modulus chains of spheres are arranged in various geometries. We observed fast splitting of the initial pulse, rapid chaotization of the signal and sharp bending of the propagating acoustic information. Pulse and energy trapping was also observed in composite systems assembled from hard- and soft-particles in the branches
Predicting C-H/ interactions with nonlocal density functional theory
We examine the performance of a recently developed nonlocal density
functional in predicting a model noncovalent interaction, the weak bond between
an aromatic system and an aliphatic C-H group. The new functional is a
significant improvement over traditional density functionals, providing results
which compare favorably to high-level quantum-chemistry techniques but at
considerably lower computational cost. Interaction energies in several model
C-H/ systems are in generally good agreement with coupled-cluster
calculations, though equilibrium distances are consistently overpredicted when
using the revPBE functional for exchange. The new functional correctly predicts
changes in energy upon addition of halogen substituents.Comment: 5 pages, 4 figure
Great Lakes all-weather ice information system
A system is described which utilizes an X-band Side-Looking-Airborne-Radar (SLAR) for determining type, location, and aerial distribution of the ice cover in the Great Lakes and an airborne, S-band, short pulse radar for obtaining ice thickness. The SLAR system is currently mounted aboard a U.S. Coast Guard C-130B aircraft. Digitized SLAR data are relayed in real-time via the NOAA-GOES-1 satellite in geosynchronous orbit to the U.S. Coast Guard Ice Center in Cleveland, Ohio. SLAR images along with hand-drawn interpretative ice charts for various winter shipping areas in the Great Lakes are broadcast to facsimile recorders aboard Great Lakes vessels. The operational aspects of this ice information system are being demonstrated by NASA, U.S. Coast Guard, and NOAA/National Weather Service. Results from the 1974-75 winter season demonstrated the ability of this system to provide all-weather ice information to shippers in a timely manner
Supercritical-fluid synthesis of FeF2 and CoF2 Li-ion conversion materials
The synthesis of the Li-ion conversion candidates, FeF2 and CoF2, obtained from the single source organometallic precursors [Fe(tta)3] (tta = C8H4F3O2S), and [Co(hfac)2[middle dot]2H2O] (hfac = C5H1F6O2), respectively, via a novel supercritical fluid (SCF) method is presented. The nature of the synthesis led to highly-crystalline FeF2 and CoF2 powders requiring no additional thermal treatment. The as-obtained powders were investigated for use as potential positive Li-ion conversion electrodes by means of chronopotentiometric measurements. The FeF2 cells displayed high initial capacities following electrochemical conversion (up to [similar]1100 mA h g-1 at a potential of 1.0 V vs. Li/Li+), with appreciable cyclic behaviour over 25 discharge-charge cycles. The deposition of a [similar]5 nm layer of amorphous carbon onto the surface of the active material following SCF treatment, likely facilitated adequate electron transport through an otherwise poorly conducting FeF2 phase. Similarly, CoF2 cells displayed high initial capacities (up to [similar]650 mA h g-1 at a potential of 1.2 V vs. Li/Li+), although significant capacity fading ensued in the subsequent cycles. Ex situ XRD measurements confirmed a poor reversibility in the conversion sequence for CoF2, with a complete loss of CoF2 crystallinity and the sole presence of a crystalline LiF phase following charging
Carbon nanocage supported synthesis of V2O5 nanorods and V2O5/TiO2 nanocomposites for Li-ion batteries
We present the facile synthesis of crystalline V2O5 nanorods and V2O5/TiO2 nanocomposites structures by a carbon nanocage (CNC)-assisted growth process, using vanadium triisopropoxide oxide and titanium isopropoxide precursors in air at 500 [degree]C. The diameters of the resultant V2O5 nanorods ranged between [similar]10 and 70 nm, while the crystalline V2O5/TiO2 nanocomposite structures adopted a unique morphology, due to both crystallisation and templating processes, with V2O5 adopting small-diameter nanowire and nanorod morphologies surrounded by sub-30 nm TiO2 nanoparticles. The V2O5 nanorods and V2O5/TiO2 nanocomposites were characterised by electron microscopy and X-ray diffraction techniques and subsequently reviewed as positive Li-ion electrodes. The phase-pure V2O5 nanorod structures exhibited appreciable Li+ storage properties over the potential range of 2.0-4.0 V vs. Li/Li+, displaying capacities of up to 288 mA h g-1 with appreciable cyclic behaviour at test rates of up to [similar]1 C. The crystalline V2O5/TiO2 nanocomposite structures displayed similar Li+ storage properties, however, increasing molar fractions of TiO2 led to a decline in the overall capacity versus the single-phase V2O5 counterparts. Interestingly, the Li+ insertion behaviour of the V2O5/TiO2 nanocomposite displayed character more-typical of amorphous V2O5, which was ascribed to a structural buffering effect of the inactive TiO2 phase
Influence of the Fermi Surface Morphology on the Magnetic Field-Driven Vortex Lattice Structure Transitions in YBaCuO0, 0.15
We report small-angle neutron scattering measurements of the vortex lattice
(VL) structure in single crystals of the lightly underdoped cuprate
superconductor YBa2Cu3O6.85. At 2 K, and for fields of up to 16 T applied
parallel to the crystal c-axis, we observe a sequence of field-driven and
first-order transitions between different VL structures. By rotating the field
away from the c-axis, we observe each structure transition to shift to either
higher or lower field dependent on whether the field is rotated towards the
[100] or [010] direction. We use this latter observation to argue that the
Fermi surface morphology must play a key role in the mechanisms that drive the
VL structure transitions. Furthermore, we show this interpretation is
compatible with analogous results obtained previously on lightly overdoped
YBa2Cu3O7. In that material, it has long-been suggested that the high field VL
structure transition is driven by the nodal gap anisotropy. In contrast, the
results and discussion presented here bring into question the role, if any, of
a nodal gap anisotropy on the VL structure transitions in both YBa2Cu3O6.85 and
YBa2Cu3O7
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