293 research outputs found
High porosity metallic glass foam: A powder metallurgy route
A powder metallurgy route to the fabrication of metallic glass foam is introduced. The method involves consolidating metallic glass powder blended with blowing agent particulates to produce expandable precursors, capable of yielding foams with porosities as high as 86%. The foams are found to inherit the strength of the parent metallic glass and to be able to deform heavily toward full densification absorbing high amounts of energy
Diffuse precordial ST-segment elevation in inferior-right myocardial infarction
A right ventricular (RV) myocardial infarction (MI) may yield precordial ST-segment elevation
(STE). Accordingly, combined inferior and precordial STE may be produced during an
inferior-RV MI. Such an electrocardiographic picture may be mistakenly regarded as showing
wrapped left anterior descending artery (LADA) occlusion or double vessel occlusion. We
present a patient with inferior-RV MI and STE in the inferior, all precordial and right chest
leads, in whom the diffuse precordial STE was probably mistakenly regarded as showing
anterior MI. However, the STE resolution in V1-V2 and late R’ wave in V1, which were
combined with a recanalized RV branch, favored the RV origin of this STE. Furthermore, the
LADA was patent when V3-V6 showed severe ischemia, while its lesion was angiographically
stable. Thus its simultaneous occlusion was unlikely. The late R’ wave in V1 indicates RV
transmural conduction delay;as highlighted herein, it is diagnostic of a RV myocardial infarction.
(Cardiol J 2010; 17, 6: 628-631
Using Hypertext to Implement Multiple Tutoring Strategies in an Intelligent Tutoring System for Music Learning
Variation in tutoring strategies plays an important part in Intelligent Tutoring Systems. The potential for providing an adaptive Intelligent Tutoring System depends on having a range of tutoring strategies to select from. In order to react effectively to the student\u27s needs, an Intelligent Tutoring System has to be able to choose intelligently among the strategies and determine which strategy is best for an individual student at a particular moment. This paper describes, through the discussion pertaining to the implementation of SONATA, a music theory tutoring system, how an Intelligent Tutoring System can be developed to support multiple tutoring strategies during the course of interaction. SONATA has been implemented using a hypertext tool, HyperCard II.1
Seasonal groundwater contribution to crop-water use assessed with lysimeter observations and model simulations
Groundwater evaporation can play an important role in crop-water use where the water table is shallow. Lysimeters are often used to quantify the groundwater evaporation contribution influenced by a broad range of environmental factors. However, it is difficult for such field facilities, which are operated under limited conditions within limited time, to capture the whole spectrum of capillary upflow with regard to the inter-seasonal variability of climate, especially rainfall. Therefore, in this work, the method of combining lysimeter and numerical experiments was implemented to investigate seasonal groundwater contribution to crop-water use. Groundwater evaporation experiments were conducted through a weighing lysimeter at an agricultural experiment station located within an irrigation district in the lower Yellow River Basin for two winter wheat growth seasons. A HYDRUS-1D model was first calibrated and validated with weighing lysimeter data, and then was employed to perform scenario simulations of groundwater evaporation under different depths to water table (DTW) and water input (rainfall plus irrigation) driven by long term meteorological data. The scenario simulations revealed that the seasonally averaged groundwater evaporation amount was linearly correlated to water input for different values of DPW. The linear regression could explain more than 70% of the variability. The seasonally averaged ratio of the groundwater contribution to crop-water use varied with the seasonal water input and DTW. The ratio reached as high as 75% in the case of DTW = 1.0 m and no irrigation, and as low as 3% in the case of DTW = 3.0 m and three irrigation applications. The results also revealed that the ratio of seasonal groundwater evaporation to potential evapotranspiration could be fitted to an exponential function of the DTW that may be applied to estimate seasonal groundwater evaporation. In this case study of multilayered soil profile, the depth at which groundwater may evaporate at potential rate was 0.60-0.65 m, and the extinction depth of groundwater evaporation was approximately 3.8 m. (C) 2010 Elsevier B.V. All rights reserved
Zero Temperature Glass Transition in the Two-Dimensional Gauge Glass Model
We investigate dynamic scaling properties of the two-dimensional gauge glass
model for the vortex glass phase in superconductors with quenched disorder.
From extensive Monte Carlo simulations we obtain static and dynamic finite
size scaling behavior, where the static simulations use a temperature exchange
method to ensure convergence at low temperatures. Both static and dynamic
scaling of Monte Carlo data is consistent with a glass transition at zero
temperature. We study a dynamic correlation function for the superconducting
order parameter, as well as the phase slip resistance. From the scaling of
these two functions, we find evidence for two distinct diverging correlation
times at the zero temperature glass transition. The longer of these time scales
is associated with phase slip fluctuations across the system that lead to
finite resistance at any finite temperature, while the shorter time scale is
associated with local phase fluctuations.Comment: 8 pages, 10 figures; v2: some minor correction
The Startle Disease Mutation E103K Impairs Activation of Human Homomeric α1 Glycine Receptors by Disrupting an Intersubunit Salt Bridge across the Agonist Binding Site
Glycine receptors (GlyR) belong to the pentameric ligand-gated ion channel (pLGIC) superfamily and mediate fast inhibitory transmission in the vertebrate CNS. Disruption of glycinergic transmission by inherited mutations produces startle disease in man. Many startle mutations are in GlyRs and provide useful clues to the function of the channel domains. E103K is one of few startle mutations found in the extracellular agonist binding site of the channel, in loop A of the principal side of the subunit interface. Homology modeling shows that the side chain of Glu-103 is close to that of Arg-131, in loop E of the complementary side of the binding site, and may form a salt bridge at the back of the binding site, constraining its size. We investigated this hypothesis in recombinant human α1 GlyR by site-directed mutagenesis and functional measurements of agonist efficacy and potency by whole cell patch clamp and single channel recording. Despite its position near the binding site, E103K causes hyperekplexia by impairing the efficacy of glycine, its ability to gate the channel once bound, which is very high in wild type GlyR. Mutating Glu-103 and Arg-131 caused various degrees of loss-of-function in the action of glycine, whereas mutations in Arg-131 enhanced the efficacy of the slightly bigger partial agonist sarcosine (N-methylglycine). The effects of the single charge-swapping mutations of these two residues were largely rescued in the double mutant, supporting the possibility that they interact via a salt bridge that normally constrains the efficacy of larger agonist molecules
Mixmaster universe in Horava-Lifshitz gravity
We consider spatially homogeneous (but generally non-isotropic) cosmologies
in the recently proposed Horava-Lifshitz gravity and compare them to those of
general relativity using Hamiltonian methods. In all cases, the problem is
described by an effective point particle moving in a potential well with
exponentially steep walls. Focusing on the closed-space cosmological model
(Bianchi type IX), the mixmaster dynamics is now completely dominated by the
quadratic Cotton tensor potential term for very small volume of the universe.
Unlike general relativity, where the evolution towards the initial singularity
always exhibits chaotic behavior with alternating Kasner epochs, the
anisotropic universe in Horava-Lifshitz gravity (with parameter lambda > 1/3)
is described by a particle moving in a frozen potential well with fixed (but
arbitrary) energy E. Alternating Kasner epochs still provide a good description
of the early universe for very large E, but the evolution appears to be
non-ergodic. For very small E there are harmonic oscillations around the fully
isotropic model. The question of chaos remains open for intermediate energy
levels.Comment: 1+35 pages, 4 figure
Intrinsic magnetism in superconducting infinite-layer nickelates
The discovery of superconductivity in NdSrNiO [1]
introduced a new family of layered nickelate superconductors that has now been
extended to include a range of Sr-doping [2, 3], Pr or La in place of Nd [4-6],
and the 5-layer NdNiO [7]. A number of studies indicate that
electron correlations are strong in these materials [8-14], and hence a central
question is whether or not magnetism is present as a consequence of these
interactions. Here we report muon spin rotation/relaxation studies of a series
of superconducting infinite-layer nickelates. In all cases we observe an
intrinsic magnetic ground state, regardless of the rare earth ion or doping,
arising from local moments on the nickel sublattice. The coexistence of
magnetism - which is likely to be antiferromagnetic and short-range ordered -
with superconductivity is reminiscent of some iron pnictides [15] and heavy
fermion compounds [16], and qualitatively distinct from the doped cuprates
[17]
Dyskinesias after neural transplantation in Parkinson's disease: what do we know and what is next?
Since the 1980 s, when cell transplantation into the brain as a cure for Parkinson's disease hit the headlines, several patients with Parkinson's disease have received transplantation of cells from aborted fetuses with the aim of replacing the dopamine cells destroyed by the disease. The results in human studies were unpredictable and raised controversy. Some patients showed remarkable improvement, but many of the patients who underwent transplantation experienced serious disabling adverse reactions, putting an end to human trials since the late 1990 s. These side effects consisted of patients' developing troublesome involuntary, uncontrolled movements in the absence of dopaminergic medication, so-called off-phase, graft-induced dyskinesias. Notwithstanding the several mechanisms having been proposed, the pathogenesis of this type of dyskinesias remained unclear and there was no effective treatment. It has been suggested that graft-induced dyskinesias could be related to fiber outgrowth from the graft causing increased dopamine release, that could be related to the failure of grafts to restore a precise distribution of dopaminergic synaptic contacts on host neurons or may also be induced by inflammatory and immune responses around the graft. A recent study, however, hypothesized that an important factor for the development of graft-induced dyskinesias could include the composition of the cell suspension and specifically that a high proportion of serotonergic neurons cografted in these transplants engage in nonphysiological properties such as false transmitter release. The findings from this study showed serotonergic hyperinnervation in the grafted striatum of two patients with Parkinson's disease who exhibited major motor recovery after transplantation with fetal mesencephalic tissue but later developed graft-induced dyskinesias. Moreover, the dyskinesias were significantly attenuated by administration of a serotonin agonist, which activates the inhibitory serotonin autoreceptors and attenuates transmitter release from serotonergic neurons, indicating that graft-induced dyskinesias were caused by the dense serotonergic innervation engaging in false transmitter release. Here the implications of the recent findings for the development of new human trials testing the safety and efficacy of cell transplantation in patients with Parkinson's disease are discussed
Cold saline irrigation of the renal pelvis during Radiofrequency Ablation of a central renal neoplasm: a case report
<p>Abstract</p> <p>Introduction</p> <p>Thermal destruction mediated by radiofrequency ablation (RFA) is gaining attention as an alternative treatment for patients with renal cell carcinoma (RCC), particularly in those who are not candidates for open surgery. Treatment of central tumours is occasionally associated with complications such as ureteric stricture, injury to the psoas muscle, haematuria and vascular laceration.</p> <p>Case presentation</p> <p>We have used infusion of cold saline during RFA, through a retrograde ureteric catheter with its tip in the renal pelvis, in a patient with a central renal tumour.</p> <p>Conclusion</p> <p>We believe this process to have successfully avoided the risk of thermal injury.</p
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