838 research outputs found
Common and distinct lateralised patterns of neural coupling during focused attention, open monitoring and loving kindness meditation
Meditation has been integrated into different therapeutic interventions. To inform the evidence-based selection of specific meditation types it is crucial to understand the neural processes associated with different meditation practices. Here we explore commonalities and differences in electroencephalographic oscillatory spatial synchronisation patterns across three important meditation types. Highly experienced meditators engaged in focused attention, open monitoring, and loving kindness meditation. Improving on previous research, our approach avoids comparisons between groups that limited previous findings, while ensuring that the meditation states are reliably established. Employing a novel measure of neural coupling – the imaginary part of EEG coherence – the study revealed that all meditation conditions displayed a common connectivity pattern that is characterised by increased connectivity of (a) broadly distributed delta networks, (b) left-hemispheric theta networks with a local integrating posterior focus, and (c) right-hemispheric alpha networks, with a local integrating parieto-occipital focus. Furthermore, each meditation state also expressed specific synchronisation patterns differentially recruiting left- or right-lateralised beta networks. These observations provide evidence that in addition to global patterns, frequency-specific inter-hemispheric asymmetry is one major feature of meditation, and that mental processes specific to each meditation type are also supported by lateralised networks from fast-frequency bands
Non-Markovian spin relaxation in two-dimensional electron gas
We analyze by Monte-Carlo simulations and analytically spin dynamics of
two-dimensional electron gas (2DEG) interacting with short-range scatterers in
nonquantizing magnetic fields. It is shown that the spin dynamics is
non-Markovian with the exponential spin relaxation followed by the oscillating
tail due to the electrons residing on the closed trajectories. The tail relaxes
on a long time scale due to an additional smooth random potential and inelastic
processes. The developed analytical theory and Monte-Carlo simulations are in
the quantitative agreement with each other.Comment: 6 pages, 3 figure
c-axis magnetotransport in CeCoIn
We present the results of out-of-plane electrical transport measurements on
the heavy fermion superconductor CeCoIn at temperatures from 40 mK to 400
K and in magnetic field up to 9 T. For 10 K transport measurements show
that the zero-field resistivity changes linearly with temperature
and extrapolates nearly to zero at 0 K, indicative of non-Fermi-liquid (nFL)
behavior associated with a quantum critical point (QCP). The longitudinal
magnetoresistance (LMR) of CeCoIn for fields applied parallel to the
c-axis is negative and scales as between 50 and 100 K, revealing
the presence of a single-impurity Kondo energy scale K.
Beginning at 16 K a small positive LMR feature is evident for fields less than
3 tesla that grows in magnitude with decreasing temperature. For higher fields
the LMR is negative and increases in magnitude with decreasing temperature.
This sizable negative magnetoresistance scales as from 2.6 K to
roughly 8 K, and it arises from an extrapolated residual resistivity that
becomes negative and grows quadratically with field in the nFL temperature
regime. Applying a magnetic field along the c-axis with B B restores
Fermi-liquid behavior in at less than 130 mK. Analysis of the
resistivity coefficient's field-dependence suggests that the QCP in
CeCoIn is located \emph{below} the upper critical field, inside the
superconducting phase. These data indicate that while high- c-axis transport
of CeCoIn exhibits features typical for a heavy fermion system, low-
transport is governed both by spin fluctuations associated with the QCP and
Kondo interactions that are influenced by the underlying complex electronic
structure intrinsic to the anisotropic CeCoIn crystal structure
Unusual giant magnetostriction in the ferrimagnet GdCaMnO
We report an unusual giant linear magnetostrictive effect in the ferrimagnet
GdCaMnO (80 K). Remarkably, the
magnetostriction, negative at high temperature (), becomes
positive below 15 K when the magnetization of the Gd sublattice overcomes the
magnetization of the Mn sublattice. A rather simple model where the magnetic
energy competes against the elastic energy gives a good account of the observed
results and confirms that Gd plays a crucial role in this unusual observation.
Unlike previous works in manganites where only striction associated with 3
Mn orbitals is considered, our results show that the lanthanide 4 orbitals
related striction can be very important too and it cannot be disregarded.Comment: 6 pages, 3 figure
Attentional and cognitive monitoring brain networks in long-term meditators depend on meditation states and expertise.
Meditation practice is suggested to engage training of cognitive control systems in the brain. To evaluate the functional involvement of attentional and cognitive monitoring processes during meditation, the present study analysed the electroencephalographic synchronization of fronto-parietal (FP) and medial-frontal (MF) brain networks in highly experienced meditators during different meditation states (focused attention, open monitoring and loving kindness meditation). The aim was to assess whether and how the connectivity patterns of FP and MF networks are modulated by meditation style and expertise. Compared to novice meditators, (1) highly experienced meditators exhibited a strong theta synchronization of both FP and MF networks in left parietal regions in all mediation styles, and (2) only the connectivity of lateralized beta MF networks differentiated meditation styles. The connectivity of intra-hemispheric theta FP networks depended non-linearly on meditation expertise, with opposite expertise-dependent patterns found in the left and the right hemisphere. In contrast, inter-hemispheric FP connectivity in faster frequency bands (fast alpha and beta) increased linearly as a function of expertise. The results confirm that executive control systems play a major role in maintaining states of meditation. The distinctive lateralized involvement of FP and MF networks appears to represent a major functional mechanism that supports both generic and style-specific meditation states. The observed expertise-dependent effects suggest that functional plasticity within executive control networks may underpin the emergence of unique meditation states in expert meditators
Behavior of the Quantum Critical Point and the Fermi-liquid Domain in the Heavy Fermion Superconductor CeCoIn5 studied by resistivity
We report detailed very low temperature resistivity measurements on the heavy
fermion compounds Ce_{1-x}La_{x}CoIn5 (x=0 and x=0.01), with current applied in
two crystallographic directions [100] (basal plane) and [001] (perpendicular to
the basal plane) under magnetic field applied in the [001] or [011] direction.
We found a Fermi liquid (\rho \propto T^{2}) ground state, in all cases, for
fields above the superconducting upper critical field. We discuss the possible
location of a field induced quantum critical point with respect to Hc2(0), and
compare our measurements with the previous reports in order to give a clear
picture of the experimental status on this long debated issue.Comment: 17 pages, 7 figures accepted for publication in JPS
Spin relaxation of conduction electrons in bulk III-V semiconductors
Spin relaxation time of conduction electrons through the Elliot-Yafet,
D'yakonov-Perel and Bir-Aronov-Pikus mechanisms is calculated theoretically for
bulk GaAs, GaSb, InAs and InSb of both - and -type. Relative importance
of each spin relaxation mechanism is compared and the diagrams showing the
dominant mechanism are constructed as a function of temperature and impurity
concentrations. Our approach is based upon theoretical calculation of the
momentum relaxation rate and allows understanding of the interplay between
various factors affecting the spin relaxation over a broad range of temperature
and impurity concentration.Comment: an error in earlier version correcte
Femtosecond control of electric currents at the interfaces of metallic ferromagnetic heterostructures
The idea to utilize not only the charge but also the spin of electrons in the
operation of electronic devices has led to the development of spintronics,
causing a revolution in how information is stored and processed. A novel
advancement would be to develop ultrafast spintronics using femtosecond laser
pulses. Employing terahertz (10 Hz) emission spectroscopy, we
demonstrate optical generation of spin-polarized electric currents at the
interfaces of metallic ferromagnetic heterostructures at the femtosecond
timescale. The direction of the photocurrent is controlled by the helicity of
the circularly polarized light. These results open up new opportunities for
realizing spintronics in the unprecedented terahertz regime and provide new
insights in all-optical control of magnetism.Comment: 3 figures and 2 tables in the main tex
Cultural singularities: indigenous elderly access to Public Health Service
OBJECTIVEDescribing how Kaingang seniors and their primary caregivers experience access to public health services.METHODA qualitative study guided by ethnography, conducted with 28 elderly and 19 caregivers. Data were collected between November 2010 and February 2013 through interviews and participative observation analyzed by ethnography.RESULTSThe study revealed the benefits and difficulties of the elderly access to health services, the facility to obtain health care resources such as appointments, medications and routine procedures, and the difficulties such as special assistance service problems and delays in the dispatching process between reference services.CONCLUSIONThe importance of knowing and understanding the cultural specificities of the group in order to offer greater opportunities for the elderly access to health services was reinforced
- …