7,633 research outputs found
Fabrication of large ceramic electrolyte disks
Process for sintering compressed ceramic powders produces large ceramic disks for use as electrolytes in high-temperature electrolytic cells. Thin, strain-free uniformly dense disks as large as 30 cm squared have been fabricated by slicing ceramic slugs produced by this technique
Properties of superdeformed fission isomers in the cranked relativistic Hartree-Bogoliubov theory
The rotational and deformation properties of superdeformed fission isomers in
the mass region have been investigated within the framework of the
cranked relativistic Hartree-Bogoliubov theory. The dependence of the results
of the calculations on the parametrization of the RMF Lagrangian has been
studied. The rotational properties are best described by the NL1 force.Comment: 5 pages, uses epsf.sty and hip-artc.sty, 1 PostScript figure,
contribution to the Proceedings of the International Symposium on Exotic
Nuclear Structures, May 15-20, 2000, Debrecen, Hungar
Superdeformations in Relativistic and Non-Relativistic Mean Field Theories
The applications of the extensions of relativistic mean field (RMF) theory to
the rotating frame, such as cranked relativistic mean field (CRMF) theory and
cranked relativistic Hartree-Bogoliubov (CRHB) theory, for the description of
superdeformed bands in the , 140-150 and 190 mass regions are
overviewed and compared briefly with the results obtained in non-relativistic
mean field theories.Comment: 18 pages including 5 figures in PostScript, requires epsf.sty,
invited talk presented at the International Conference on Achievements and
Perspectives in Nuclear Structure, Crete, Greece, July 11-17, 1999, will be
published in Physica Script
Cranked relativistic Hartree-Bogoliubov theory: Superdeformation in the mass region
A systematic investigation of the yrast superdeformed (SD) rotational bands
in even-even nuclei of the mass region has been performed within
the framework of the cranked relativistic Hartree-Bogoliubov theory. The
particle-hole channel of this theory is treated fully relativistically, while a
finite range two-body force of Gogny type is used in the particle-particle
(pairing) channel. Using the well established parameter sets NL1 for the
Lagrangian and D1S for the Gogny force, very good description of experimental
data is obtained with no adjustable parameters.Comment: 5 pages, 2 Postscript figures, uses sprocl.sty, contribution to the
Proceedings of the International Conference ``Bologna 2000, Structure of the
Nucleus at the Dawn of the Century'
Practice makes efficient: Effects of golf practice on brain activity
This study employed a test-retest design to examine changes in brain activity associated with practice of a motor skill. We recorded EEG activity from twelve right-handed recreational golfers (mean handicap: 23) as they putted 50 balls to a 2.4m distant hole, before and after a 3-day practice. We measured changes in putting performance, conscious processing, and regional EEG alpha activity. Putting performance improved and conscious processing decreased after practice. Mediation analyses revealed that performance improvements were associated with changes in EEG alpha, whereby activity in task-irrelevant cortical regions (temporal regions) was inhibited and functionally isolated from activity in task-relevant regions (central regions). These findings provide evidence for the development of greater neurophysiological efficiency with practice of a motor skill
Eye quietness and quiet eye in expert and novice golf performance: an electrooculographic analysis
Quiet eye (QE) is the final ocular fixation on the target of an action (e.g., the ball in golf putting). Camerabased eye-tracking studies have consistently found longer QE durations in experts than novices; however, mechanisms underlying QE are not known. To offer a new perspective we examined the feasibility of measuring the QE using electrooculography (EOG) and developed an index to assess ocular activity across time: eye quietness (EQ). Ten expert and ten novice golfers putted 60 balls to a 2.4 m distant hole. Horizontal EOG (2ms resolution) was recorded from two electrodes placed on the outer sides of the eyes. QE duration was measured using a EOG voltage threshold and comprised the sum of the pre-movement and post-movement initiation components. EQ was computed as the standard deviation of the EOG in 0.5 s bins from –4 to +2 s, relative to backswing initiation: lower values indicate less movement of the eyes, hence greater quietness. Finally, we measured club-ball address and swing durations. T-tests showed that total QE did not differ between groups (p = .31); however, experts had marginally shorter pre-movement QE (p = .08) and longer post-movement QE (p < .001) than novices. A group × time ANOVA revealed that experts had less EQ before
backswing initiation and greater EQ after backswing initiation (p = .002). QE durations were inversely correlated with EQ from –1.5 to 1 s (rs = –.48 - –.90, ps = .03 - .001). Experts had longer swing durations than novices (p = .01) and, importantly, swing durations correlated positively with post-movement QE (r = .52, p = .02) and negatively with EQ from 0.5 to 1s (r = –.63, p = .003). This study demonstrates the feasibility of measuring ocular activity using EOG and validates EQ as an index of ocular activity. Its findings challenge the dominant perspective on QE and provide new evidence that expert-novice differences in ocular activity may reflect differences in the kinematics of how experts and novices execute skills
Fission barriers in actinides in covariant density functional theory: the role of triaxiality
Relativistic mean field theory allowing for triaxial deformations is applied
for a systematic study of fission barriers in the actinide region. Different
pairing schemes are studied in details and it is shown that covariant density
functional theory is able to describe fission barriers on a level of accuracy
comparable with non-relativistic calculations, even with the best
phenomenological macroscopic+microscopic approaches. Triaxiality in the region
of the first saddle plays a crucial role in achieving that.Comment: 11 pages, 13 figure
Nuclear fission in covariant density functional theory
The current status of the application of covariant density functional theory
to microscopic description of nuclear fission with main emphasis on superheavy
nuclei (SHN) is reviewed. The softness of SHN in the triaxial plane leads to an
emergence of several competing fission pathes in the region of the inner
fission barrier in some of these nuclei. The outer fission barriers of SHN are
considerably affected both by triaxiality and octupole deformation.Comment: 6 pages, 4 figures, will be published in European Physical Journal,
Web of Conferences, (Proceedings of Fifth International Workshop on Nuclear
fission and Fission-Product Spectroscopy
- …