11,239 research outputs found
Satellite land use acquisition and applications to hydrologic planning models
A developing operational procedure for use by the Corps of Engineers in the acquisition of land use information for hydrologic planning purposes was described. The operational conditions preclude the use of dedicated, interactive image processing facilities. Given the constraints, an approach to land use classification based on clustering seems promising and was explored in detail. The procedure is outlined and examples of application to two watersheds given
Dynamics of Bond Market Integration between Existing And Accession EU Countries
In this paper, we use a set of complementary techniques to examine the time-varying level of integration of European government bond markets. We consider daily bond returns and prices over the 1998-2003 period. Strong contemporaneous and dynamic linkages are found between individual European Union (EU) markets and the German market. However, there is no such evidence for the three accession markets of the Czech Republic, Hungary and Poland. The UK’s market is also considered. In general, the degree of integration for the accession markets is weak and stable, with little evidence of further deepening despite the increased political integration.Bond Indices, Cointegration, GARCH Models, Integration, Kalman Filter
A study of the use of remote sensing data in hydrologic engineering models
There are no author-identified significant results in this report
X-ray and EUV Observations of Simultaneous Short and Long Period Oscillations in Hot Coronal Arcade Loops
We report decaying quasi-periodic intensity oscillations in the X-ray (6-12
keV) and extreme ultraviolet (EUV) channels (131, 94, 1600, 304 \AA) observed
by the Fermi GBM (Gamma-ray Burst Monitor) and SDO/AIA, respectively, during a
C-class flare. The estimated period of oscillation and decay time in the X-ray
channel (6-12 keV) was about 202 s and 154 s, respectively. A similar
oscillation period was detected at the footpoint of the arcade loops in the AIA
1600 and 304 \AA channels. Simultaneously, AIA hot channels (94 and 131 \AA)
reveal propagating EUV disturbances bouncing back and forth between the
footpoints of the arcade loops. The period of the oscillation and decay time
were about 409 s and 1121 s, respectively. The characteristic phase speed of
the wave is about 560 km/s for about 115 Mm loop length, which is roughly
consistent with the sound speed at the temperature about 10-16 MK (480-608
km/s). These EUV oscillations are consistent with the SOHO/SUMER Doppler-shift
oscillations interpreted as the global standing slow magnetoacoustic wave
excited by a flare. The flare occurred at one of the footpoints of the arcade
loops, where the magnetic topology was a 3D fan-spine with a null-point.
Repetitive reconnection at this footpoint could cause the periodic acceleration
of non-thermal electrons that propagated to the opposite footpoint along the
arcade and precipitating there, causing the observed 202-s periodicity. Other
possible interpretations, e.g. the second harmonics of the slow mode are also
discussed.Comment: ApJ (in press), 13 pages, 6 figure
Midazolam Efficacy Against Acute Hydrogen Sulfide-Induced Mortality and Neurotoxicity.
Hydrogen sulfide (H2S) is a colorless, highly neurotoxic gas. It is not only an occupational and environmental hazard but also of concern to the Department of Homeland Security for potential nefarious use. Acute high-dose H2S exposure causes death, while survivors may develop neurological sequelae. Currently, there is no suitable antidote for treatment of acute H2S-induced neurotoxicity. Midazolam (MDZ), an anti-convulsant drug recommended for treatment of nerve agent intoxications, could also be of value in treating acute H2S intoxication. In this study, we tested the hypothesis that MDZ is effective in preventing/treating acute H2S-induced neurotoxicity. This proof-of-concept study had two objectives: to determine whether MDZ prevents/reduces H2S-induced mortality and to test whether MDZ prevents H2S-induced neurological sequelae. MDZ (4 mg/kg) was administered IM in mice, 5 min pre-exposure to a high concentration of H2S at 1000 ppm or 12 min post-exposure to 1000 ppm H2S followed by 30 min of continuous exposure. A separate experiment tested whether MDZ pre-treatment prevented neurological sequelae. Endpoints monitored included assessment of clinical signs, mortality, behavioral changes, and brain histopathological changes. MDZ significantly reduced H2S-induced lethality, seizures, knockdown, and behavioral deficits (p < 0.01). MDZ also significantly prevented H2S-induced neurological sequelae, including weight loss, behavior deficits, neuroinflammation, and histopathologic lesions (p < 0.01). Overall, our findings show that MDZ is a promising drug for reducing H2S-induced acute mortality, neurotoxicity, and neurological sequelae
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Broad spectrum proteomics analysis of the inferior colliculus following acute hydrogen sulfide exposure.
Acute exposure to high concentrations of H2S causes severe brain injury and long-term neurological disorders, but the mechanisms involved are not known. To better understand the cellular and molecular mechanisms involved in acute H2S-induced neurodegeneration we used a broad-spectrum proteomic analysis approach to identify key molecules and molecular pathways involved in the pathogenesis of acute H2S-induced neurotoxicity and neurodegeneration. Mice were subjected to acute inhalation exposure of up to750 ppm of H2S. H2S induced behavioral deficits and severe lesions including hemorrhage in the inferior colliculus (IC). The IC was microdissected for proteomic analysis. Tandem mass tags (TMT) liquid chromatography mass spectrometry (LC-MS/MS)-based quantitative proteomics was applied for protein identification and quantitation. LC-MS/MS identified 598, 562, and 546 altered proteomic changes at 2 h, and on days 2 and 4 post-H2S exposure, respectively. Of these, 77 proteomic changes were statistically significant at any of the 3 time points. Mass spectrometry data were subjected to Perseus 1.5.5.3 statistical analysis, and gene ontology heat map clustering. Expressions of several key molecules were verified to confirm H2S-dependent proteomics changes. Webgestalt pathway overrepresentation enrichment analysis with Panther engine revealed H2S exposure disrupted several biological processes including metabotropic glutamate receptor group 1 and inflammation mediated by chemokine and cytokine signaling pathways among others. Further analysis showed that energy metabolism, integrity of blood-brain barrier, hypoxic, and oxidative stress signaling pathways were also implicated. Collectively, this broad-spectrum proteomics data has provided important clues to follow up in future studies to further elucidate mechanisms of H2S-induced neurotoxicity
Electrical spin injection and detection in an InAs quantum well
We demonstrate fully electrical detection of spin injection in InAs quantum
wells. A spin polarized current is injected from a NiFe thin film to a
two-dimensional electron gas (2DEG) made of InAs based epitaxial multi-layers.
Injected spins accumulate and diffuse out in the 2DEG, and the spins are
electrically detected by a neighboring NiFe electrode. The observed spin
diffusion length is 1.8 um at 20 K. The injected spin polarization across the
NiFe/InAs interface is 1.9% at 20 K and remains at 1.4% even at room
temperature. Our experimental results will contribute significantly to the
realization of a practical spin field effect transistor
Fundamental Limits to Coherent Photon Generation with Solid-State Atomlike Transitions
Coherent generation of indistinguishable single photons is crucial for many
quantum communication and processing protocols. Solid-state realizations of
two-level atomic transitions or three-level spin- systems offer
significant advantages over their atomic counterparts for this purpose, albeit
decoherence can arise due to environmental couplings. One popular approach to
mitigate dephasing is to operate in the weak excitation limit, where excited
state population is minimal and coherently scattered photons dominate over
incoherent emission. Here we probe the coherence of photons produced using
two-level and spin- solid-state systems. We observe that the coupling
of the atomic-like transitions to the vibronic transitions of the crystal
lattice is independent of driving strength and detuning. We apply a polaron
master equation to capture the non-Markovian dynamics of the ground state
vibrational manifolds. These results provide insight into the fundamental
limitations for photon coherence from solid-state quantum emitters, with the
consequence that deterministic single-shot quantum protocols are impossible and
inherently probabilistic approaches must be embraced.Comment: 16 pages [with supplementary information], 8 figure
Quasi-periodic radio bursts associated with fast-mode waves near a magnetic null point
This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ~664–1416 km s−1. Almost simultaneously, quasi-periodic bursts with similar instant periods, ~70 and ~140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of the flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s−1. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops
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