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Search Results: 1 - 10 of 346623 matches for " G. D. Thompson "
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Uncertainty in climate change projections of discharge for the Mekong River Basin
D. G. Kingston, J. R. Thompson,G. Kite
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: The Mekong River Basin is a key regional resource in Southeast Asia for sectors that include agriculture, fisheries and electricity production. Here we explore the potential impacts of climate change on freshwater resources within the river basin. We quantify uncertainty in these projections associated with GCM structure and climate sensitivity, as well as from hydrological model parameter specification. This is achieved by running pattern-scaled GCM scenarios through a semi-distributed hydrological model (SLURP) of the basin. Pattern-scaling allows investigation of specific thresholds of global climate change including the postulated 2 °C threshold of "dangerous" climate change. Impacts of a 2 °C rise in global mean temperature are investigated using seven different GCMs, providing an implicit analysis of uncertainty associated with GCM structure. Analysis of progressive changes in global mean temperature from 0.5 to 6 °C above the 1961–1990 baseline (using the HadCM3 GCM) reveals a relatively small but non-linear response of annual river discharge to increasing global mean temperature, ranging from a 5.4 % decrease to 4.5 % increase. Changes in mean monthly river discharge are greater (from 16 % to +55 %, with greatest decreases in July and August, greatest increases in May and June) and result from complex and contrasting intra-basin changes in precipitation, evaporation and snow storage/melt. Whilst overall results are highly GCM dependent (in both direction and magnitude), this uncertainty is primarily driven by differences in GCM projections of future precipitation. In contrast, there is strong consistency between GCMs in terms of both increased potential evapotranspiration and a shift to an earlier and less substantial snowmelt season. Indeed, in the upper Mekong (Lancang sub-basin), the temperature-related signal in discharge is strong enough to overwhelm the precipitation-related uncertainty in the direction of change in discharge, with scenarios from all GCMs leading to increased river flow from April–June and decreased flow from July–August.
Uncertainty in climate change projections of discharge for the Mekong River Basin
D. G. Kingston,J. R. Thompson,G. Kite
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-5991-2010
Abstract: The Mekong River Basin comprises a key regional resource in Southeast Asia for sectors that include agriculture, fisheries and electricity production. Here we explore the potential impacts of climate change on freshwater resources within the river basin. We quantify uncertainty in these projections associated with GCM structure and climate sensitivity, as well as from hydrological model parameter specification. This is achieved by running pattern-scaled GCM output through a semi-distributed hydrological model (SLURP) of the basin. These pattern-scaled GCM outputs allow investigation of specific thresholds of global climate change including the postulated 2 oC threshold of "dangerous" climate change as simulated using outputs from seven different GCMs. Detailed analysis of results based on HadCM3 climate scenarios reveals a relatively small but non-linear response of annual river discharge to increasing global mean temperature, ranging from a 5.4% decrease to 4.5% increase. Intra-annual (monthly) changes in river discharge are greater (from 16% to +55%, with greatest decreases in July and August, greatest increases in May and June) and result from complex and contrasting intra-basin changes in precipitation, evaporation and snow storage/melt. Whilst overall results are highly GCM dependent (in both direction and magnitude), this uncertainty is primarily driven by differences in GCM projections of future precipitation. In contrast, there is strong consistency between GCMs in terms of both increased potential evapotranspiration and a shift to an earlier and less substantial snowmelt season. Indeed, in the upper Mekong (Lancang sub-basin), the temperature-related signal in discharge is strong enough to overwhelm the precipitation-related uncertainty in the direction of change in discharge, with scenarios from all GCMs leading to increased river flow from April–June, and decreased flow from July–August.
Physiology and Pathophysiology of the Swallowing Area of Human Motor Cortex
S. Hamdy,Q. Aziz,D. G. Thompson,J. C. Rothwell
Neural Plasticity , 2001, DOI: 10.1155/np.2001.91
Abstract: Swallowing problems can affect as many as one in three patients in the period immediately after stroke. Despite this, in the majority of cases, recovery usually occurs to a safe level after a month or two. In this review, we show. how the organization of the cortical projections to swallowing nuscles can account for many of the clinical observations on swallowing after stroke and explain why recovery is common in the long term. In addition, we examine approaches that may be useful in speeding up recovery of swallowing. Swallowing may be a useful model in which to study central nervous reorganization after injury.
Examples of fast solar wind transients, their sources and the forecast of possible geomagnetic impact
D. Berdichevsky,I.G. Richardson,B.J. Thompson,D.V. Reames
Geofísica internacional , 2000,
Abstract: We present examples of solar ejecta, including possible interplanetary magnetic clouds, which generated fast forward interplanetary shocks as they moved rapidly through the interplanetary medium. These events occurred before and during the ISTP era. The example from 1982, close to solar maximum, was observed by the SOLWIND, ISEE, HELIOS, and IMP spacecraft which provide wide coverage of the Sun and inner heliosphere. The second event occurred on May 1998. A detailed description of its solar origin is provided by observations from instruments on the SOHO spacecraft, while observations of the shock-generated radio emissions and energetic particles and near-earth solar wind magnetic fields and plasmas are provided by the Wind spacecraft. We revisit potential tools for space weather forecasting, namely: the power of monitoring the Sun with sensors located within a wide range of heliospheric longitudes and distances, the high resolution in time and light-intensity of the extreme ultraviolet imager and solar coronograph, the remote sensing of drifting radio emissions and the local observation of MeV energetic ions.
Measurement of low energy charge correlations in underdoped spin-glass La-based cuprates using impedance spectroscopy
G. R. Jelbert,T. Sasagawa,J. D. Fletcher,T. Park,J. D. Thompson,C. Panagopoulos
Physics , 2008, DOI: 10.1103/PhysRevB.78.132513
Abstract: We report on the charge kinetics of La_2CuO_4 lightly doped with Li and Sr. Impedance spectroscopy measurements down to 25mK and from 20Hz to 500kHz reveal evidence for low energy charge dynamics, which slow down with decreasing temperature. Both systems are acutely sensitive to stoichiometry. In the case of Sr substitution, which at higher carrier concentration evolves to a high temperature superconductor, the ground state in the pseudogap-doping regime is one of spatially segregated, dynamic charge domains. The charge carriers slow down at substantially lower temperatures than their spin counterparts and the dynamics are particularly sensitive to crystallographic direction. This is contrasted with the case of Li-doping.
Cooling for instantons and the Wrath of Nahm
S. Bilson-Thompson,F. D. R. Bonnet,D. B. Leinweber,A. G. Williams
Physics , 2001, DOI: 10.1016/S0920-5632(02)01399-3
Abstract: The dynamics of instantons and anti-instantons in lattice QCD can be studied by analysing the action and topological charge of configurations as they approach a self-dual or anti-self-dual state, i.e. a state in which S/S_0=|Q|. We use cooling to reveal the semi-classical structure of the configurations we study. Improved actions which eliminate discretization errors up to and including O(a^4) are used to stabilise instantons as we cool for several thousand sweeps. An analogously improved lattice version of the continuum field-strength tensor is used to construct a topological charge free from O(a^4) discretization errors. Values of the action and topological charge obtained with these improved operators approach mutually-consistent integer values to within a few parts in 10^4 after several hundred cooling sweeps. Analysis of configurations with |Q| \approx 1 and |Q| \approx 2 supports the hypothesis that a self-dual |Q|=1 configuration cannot exist on the 4-torus.
Coherence and Raman sideband cooling of a single atom in an optical tweezer
J. D. Thompson,T. G. Tiecke,A. S. Zibrov,V. Vuleti?,M. D. Lukin
Physics , 2012, DOI: 10.1103/PhysRevLett.110.133001
Abstract: We investigate quantum control of a single atom in an optical tweezer trap created by a tightly focused optical beam. We show that longitudinal polarization components in the dipole trap arising from the breakdown of the paraxial approximation give rise to significant internal-state decoherence. We show that this effect can be mitigated by appropriate choice of magnetic bias field, enabling Raman sideband cooling of a single atom close to its three-dimensional ground state in an optical trap with a beam waist as small as $w=900$ nm. We achieve vibrational occupation numbers of $\bar{n}_r = 0.01$ and $\bar{n}_a = 8$ in the radial and axial directions of the trap, corresponding to an rms size of the atomic wavepacket of 24 nm and 270 nm, respectively. This represents a promising starting point for future hybrid quantum systems where atoms are placed in close proximity to surfaces.
Beyond HDF - Searching for Early Star Formation in the Infrared
D. Thompson
Physics , 1997,
Abstract: The success of the Hubble Deep Field (HDF) data in identifying galaxies at redshifts up to ~3 has been quite spectacular. It is possible to extend this to even higher redshifts using infrared techniques, several of which are briefly described in this paper.
Evolution of the heavy fermion state in Ce2IrIn8
R. H. Heffner,G. D. Morris,E. D. Bauer,J. L. Sarrao,J. D. Thompson,D. E. MacLaughlin,L. Shu
Physics , 2005, DOI: 10.1016/j.physb.2005.11.048
Abstract: We report muon spin rotation Knight shift and susceptibility studies for 1 T applied field along the crystalline c- and a-axes of the heavy fermion compound Ce2IrIn8. Below a characteristic temperature T* one observes a `Knight-shift anomaly' in which the Knight shift constant K no longer scales linearly with susceptibility chi. This anomaly is consistent with a scaling law in which chi is composed of a high-temperature component corresponding to non-interacting local moments and a low-temperature component chi_cf proportional to (1-T/T*)\ln(T*/T) which characterizes the heavy-electron state below T*. We find that T* is anisotropic, with T_a* = 59(3)K and T_c* = 24(1)K, and derive the magnitudes of chi_cf for H along the a- and c-axes.
Planned Neck Dissection Following Radiation Treatment for Head and Neck Malignancy
J. F. Dautremont,M. K. Brake,G. Thompson,J. Trites,R. D. Hart,S. M. Taylor
International Journal of Otolaryngology , 2012, DOI: 10.1155/2012/954203
Abstract: Introduction. Optimal therapy for patients with metastatic neck disease remains controversial. Neck dissection following radiotherapy has traditionally been used to improve locoregional control. Methods. A retrospective review of 28 patients with node-positive head and neck malignancy treated with planned neck dissection following radiotherapy between January 2002 and December 2005 was performed to assess treatment outcomes. Results. Median interval to neck dissection was 9.6 weeks with a median number of 21
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