1,636 research outputs found
Magnetization structure of a Bloch point singularity
Switching of magnetic vortex cores involves a topological transition
characterized by the presence of a magnetization singularity, a point where the
magnetization vanishes (Bloch point). We analytically derive the shape of the
Bloch point that is an extremum of the free energy with exchange, dipole and
the Landau terms for the determination of the local value of the magnetization
modulus.Comment: 4 pages, 2 figure
The Accuracy of Beliefs About Retrieval Cues
We investigated the accuracy of predictions about semantic, environmental, and phonological cues for remembering. Subjects rated the pleasantness of 10 words in each of four rooms, predicted the number of words that they would recall with and without one of the three types of cues, and then were tested for free or cued recall. Consistent with their predictions, subjects who received semantic cues recalled more words than did subjects in the free-recall group. The subjects in the other cuing conditions did not benefit from the cues; furthermore, they overestimated the value of phonological cues, and they believed that environmental cues were ineffective. Finally, confidence ratings for cued-recall predictions did not reflect the pattern of cued-recall performance. Subjects were least confident about their predictions for semantic cuing and most confident about their predictions for recall to be cued phonologically
Effects of Alcohol and Expectancy Upon Episodic Memory in Individuals Reporting Alcoholic Blackouts
In a within-subject placebo design, 10 heavy drinkers reporting alcoholic blackouts showed significant decrements in episodic memory when receiving alcohol but not on days when a placebo was given. Parallel deficits were observed on recall and recognition measures. On placebo days, self-ratings of intoxication were related to the degree of observed performance decrement. Memory deficits appear to be primarily pharmacologic rather than expectancy effects of drinking
Conductance of Distorted Carbon Nanotubes
We have calculated the effects of structural distortions of armchair carbon
nanotubes on their electrical transport properties. We found that the bending
of the nanotubes decreases their transmission function in certain energy ranges
and leads to an increased electrical resistance. Electronic structure
calculations show that these energy ranges contain localized states with
significant - hybridization resulting from the increased curvature
produced by bending. Our calculations of the contact resistance show that the
large contact resistances observed for SWNTs are likely due to the weak
coupling of the NT to the metal in side bonded NT-metal configurations.Comment: 5 pages RevTeX including 4 figures, submitted to PR
Cognitive Effort and Memory
We propose that the concept of cognitive effort in memory is both useful and important. Cognitive effort is defined as the engaged proportion of limited-capacity central processing. It·was hypothesized that this variable might have important memorial consequences and might also be a potential confounding factor in levels-of-processing paradigms. The first experiment tested this possibility using two types of incidental-learning tasks factorially combined with two degrees of effort. It was found that high effort led to better recall than low effort, but that level-of-processing effects were nonsignificant. A second experiment clearly demonstrated the feasibility of using performance on a secondary task as an independent criterion for measuring effort, and two further experiments ruled out alternative accounts of effort effects. A reliable levels-of-processing effect was obtained in the fourth experiment in which the incidental-learning tasks were blocked. Implications and possible future applications of the cognitive effort concept are discussed
Growth in densely populated Asia: implications for primary product exporters
Economic growth and integration in Asia is rapidly increasing the global economic importance of the region. To the extent that this growth continues and is strongest in natural resource-poor Asian economies, it will add to global demand for imports of primary products, to the benefit of (especially nearby) resource-abundant countries. How will global production, consumption and trade patterns change by 2030 in the course of such economic developments and structural changes? We address this question using the GTAP model and Version 8.1 of the 2007 GTAP database, together with supplementary data from a range of sources, to support projections of the global economy from 2007 to 2030 under various scenarios. Factor endowments and real gross domestic product are assumed to grow at exogenous rates, and trade-related policies are kept unchanged to generate a core baseline, which is compared with an alternative slower growth scenario. We also consider the impact of several policy changes aimed at increasing China's agricultural self-sufficiency relative to the 2030 baseline. Policy implications for countries of the Asia-Pacific region are drawn out in the final section
Coverage-dependent adsorption sites in the K/Ru(0001) system: a low-energy electron-diffraction analysis
The two ordered phases p(2 × 2) at a coverage θ = 0.25 and (√3 × √3)R30° at θ = 0.33 of potassium adsorbed on Ru(0001) were analyzed by use of low-energy electron-diffraction (LEED). In the (√3 × √3)R30° phase, the K atoms occupy threefold hcp sites, while in the p(2 × 2) phase the fcc site is favoured. In both phases, the K hard-sphere radii are nearly the same and close to the covalent Pauling radius
Time-dependent screening of a positive charge distribution in metals: Excitons on an ultra-short time scale
Experiments determining the lifetime of excited electrons in crystalline
copper reveal states which cannot be interpreted as Bloch states [S. Ogawa {\it
et al.}, Phys. Rev. B {\bf 55}, 10869 (1997)]. In this article we propose a
model which explains these states as transient excitonic states in metals. The
physical background of transient excitons is the finite time a system needs to
react to an external perturbation, in other words, the time which is needed to
build up a polarization cloud. This process can be probed with modern
ultra-short laser pulses. We calculate the time-dependent density-response
function within the jellium model and for real Cu. From this knowledge it is
possible within linear response theory to calculate the time needed to screen a
positive charge distribution and -- on top of this -- to determine excitonic
binding energies. Our results lead to the interpretation of the experimentally
detected states as transient excitonic states.Comment: 24 pages, 9 figures, to appear in Phys. Rev. B, Nov. 15, 2000, issue
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