1,273 research outputs found
Cortical electrical activity changes in healthy aging using EEG-eLORETA analysis
Brain aging causes loss of synaptic spines, neuronal apoptosis, and a reduction in neurotransmitter levels. These aging phenomena disturb cortical electrical activity and its synchronization with connected regions. Previous electroencephalography (EEG) studies reported an age-related decrease in electrical activity in the alpha frequency band at occipital, parietal, and temporal areas as well as a decrease in occipital delta activity. However, there is an ongoing debate about whether there is an increase or decrease of the activity in other frequency bands with aging due to inconsistent study findings. In this study, we aimed to detect age-related changes of cortical electrical activities in all five frequency bands (delta, theta, alpha, beta, and gamma) in a large sample of healthy subjects for the first time. Using eLORETA (exact low-resolution brain electromagnetic tomography) analysis, we applied an eLORETA source estimation method to resting-state EEG data in 147 healthy subjects (median age 55, IQR 26.5–67.0) to obtain cortical electrical activity and assessed age-related changes in this activity using correlation analysis with multiple comparison correction. The combination of the eLORETA source estimation method and correlation analysis implemented in eLORETA software detected age-related changes in specific cortical regions for each frequency band: (1) delta and theta cortical electrical activities decreased at the occipital area with age, (2) alpha cortical electrical activity decreased at the occipitoparietotemporal areas with age, (3) beta cortical electrical activity increased at the insula, sensorimotor area, supplementary motor area, premotor area, and right temporal areas with age (most significant correlation at the right insula), (4) gamma cortical electrical activity increased at the frontoparietal and left temporal areas with age. These findings extend previous EEG study findings and provide valuable information related to mechanisms of healthy aging. Overall, our findings revealed that even healthy aging greatly affects cortical electrical activities in a region-specific way
Quantum Monte Carlo Simulation of the Trellis Lattice Heisenberg Model for SrCuO and CaVO
We study the spin-1/2 trellis lattice Heisenberg model, a coupled spin ladder
system, both by perturbation around the dimer limit and by quantum Monte Carlo
simulations. We discuss the influence of the inter-ladder coupling on the spin
gap and the dispersion, and present results for the temperature dependence of
the uniform susceptibility. The latter was found to be parameterized well by a
mean-field type scaling ansatz. Finally we discuss fits of experimental
measurements on SrCuO and CaVO to our results.Comment: 7 pages, 8 figure
Diffuse Neutron Scattering Study of a Disordered Complex Perovskite Pb(Zn1/3Nb2/3)O3 Crystal
Diffuse scattering around the (110) reciprocal lattice point has been
investigated by elastic neutron scattering in the paraelectric and the relaxor
phases of the disordered complex perovskite crystal-Pb(Zn1/3Nb2/3)O3(PZN). The
appearance of a diffuse intensity peak indicates the formation of polar
nanoregions at temperature T*, approximately 40K above Tc=413K. The analysis of
this diffuse scattering indicates that these regions are in the shape of
ellipsoids, more extended in the direction than in the direction.
The quantitative analysis provides an estimate of the correlation length, \xi,
or size of the regions and shows that \xi ~1.2\xi , consistent with
the primary or dominant displacement of Pb leading to the low temperature
rhombohedral phase. Both the appearance of the polar regions at T*and the
structural transition at Tc are marked by kinks in the \xi curve but not
in the \xi one, also indicating that the primary changes take place in a
direction at both temperatures.Comment: REVTeX file. 4 pages, 3 figures embedded, New version after referee
cond-mat/010605
Autonomous and reversible adhesion using elastomeric suction cups for in-vivo medical treatments
Remotely controllable and reversible adhesion is highly desirable for surgical operations: it can provide the possibility of non-invasive surgery, flexibility in fixing a patch and surgical manipulation via sticking. In our previous work, we developed a remotely controllable, ingestible, and deployable pill for use as a patch in the human stomach. In this study, we focus on magnetically facilitated reversible adhesion and develop a suction-based adhesive mechanism as a solution for non-invasive and autonomous adhesion of patches. We present
the design, model, and fabrication of a magnet-embedded
elastomeric suction cup. The suction cup can be localised,
navigated, and activated or deactivated in an autonomous way;
all realised magnetically with a pre-programmed fashion. The
use of the adhesion mechanism is demonstrated for anchoring
and carrying, for patching an internal organ surface and for
an object removal, respectively
Various series expansions for a Heisenberg antiferromagnet model for SrCu(BO)
We use a variety of series expansion methods at both zero and finite
temperature to study an antiferromagnetic Heisenberg spin model proposed
recently by Miyahara and Ueda for the quasi two-dimensional material
SrCu(BO). We confirm that this model exhibits a first-order quantum
phase transition at T=0 between a gapped dimer phase and a gapless N\'eel phase
when the ratio of nearest and next-nearest neighbour interactions is
varied, and locate the transition at . Using longer series we are
able to give more accurate estimates of the model parameters by fitting to the
high temperature susceptibility data.Comment: RevTeX, 13 figure
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