725 research outputs found
Altered functional brain network connectivity and glutamate system function in transgenic mice expressing truncated Disrupted-in-Schizophrenia 1
Considerable evidence implicates DISC1 as a susceptibility gene for multiple psychiatric diseases. DISC1 has been intensively studied at the molecular, cellular and behavioral level, but its role in regulating brain connectivity and brain network function remains unknown. Here, we utilize a set of complementary approaches to assess the functional brain network abnormalities present in mice expressing a truncated Disc1 gene (Disc1tr Hemi mice). Disc1tr Hemi mice exhibited hypometabolism in the prefrontal cortex (PFC) and reticular thalamus along with a reorganization of functional brain network connectivity that included compromised hippocampal–PFC connectivity. Altered hippocampal–PFC connectivity in Disc1tr Hemi mice was confirmed by electrophysiological analysis, with Disc1tr Hemi mice showing a reduced probability of presynaptic neurotransmitter release in the monosynaptic glutamatergic hippocampal CA1–PFC projection. Glutamate system dysfunction in Disc1tr Hemi mice was further supported by the attenuated cerebral metabolic response to the NMDA receptor (NMDAR) antagonist ketamine and decreased hippocampal expression of NMDAR subunits 2A and 2B in these animals. These data show that the Disc1 truncation in Disc1tr Hemi mice induces a range of translationally relevant endophenotypes underpinned by glutamate system dysfunction and altered brain connectivity
Nonlinear low frequency gravity waves in a water-filled cylindrical vessel subjected to high frequency excitations
In the experiments of a water storage cylindrical shell, excited by a horizontal external force of sufficient large amplitude and high frequency, it has been observed that gravity water waves of low frequencies may be generated. This paper intends to investigate this phenomenon in order to reveal its mechanism. Considering nonlinear fluid–structure interactions, we derive the governing equations and the numerical equations describing the dynamics of the system, using a variational principle. Following the developed generalized equations, a four-mode approximation model is proposed with which an experimental case example is studied. Numerical calculation and spectrum analysis demonstrate that an external excitation with sufficient large amplitude and high frequency can produce gravity water waves with lower frequencies. The excitation magnitude and frequencies required for onset of the gravity waves are found based on the model. Transitions betweendifferent gravity waves are also revealed through the numerical analysis. The findings developed by this method are validated by available experimental observations
Amplification of evanescent waves in a lossy left-handed material slab
We carry out finite-difference time-domain (FDTD) simulations, with a
specially-designed boundary condition, on pure evanescent waves interacting
with a lossy left-handed material (LHM) slab. Our results provide the first
full-wave numerical evidence for the amplification of evanescent waves inside a
LHM slab of finite absorption. The amplification is due to the interactions
between the evanescent waves and the coupled surface polaritons at the two
surfaces of the LHM slab and the physical process can be described by a simple
model.Comment: 4 pages, 2 figure
The Interspersed Spin Boson Lattice Model
We describe a family of lattice models that support a new class of quantum
magnetism characterized by correlated spin and bosonic ordering [Phys. Rev.
Lett. 112, 180405 (2014)]. We explore the full phase diagram of the model using
Matrix-Product-State methods. Guided by these numerical results, we describe a
modified variational ansatz to improve our analytic description of the
groundstate at low boson frequencies. Additionally, we introduce an
experimental protocol capable of inferring the low-energy excitations of the
system by means of Fano scattering spectroscopy. Finally, we discuss the
implementation and characterization of this model with current circuit-QED
technology.Comment: Submitted to EPJ ST issue on "Novel Quantum Phases and Mesoscopic
Physics in Quantum Gases
Stress Dependence of Exciton Relaxation Processes in Cu2O
A comprehensive study of the exciton relaxation processes in Cu2O has led to
some surprises. We find that the ortho-para conversion rate becomes slower at
high stress, and that the Auger nonradiative recombination rate increases with
stress, with apparently no Auger recombination at zero stress. These results
have important consequences for the pursuit of Bose-Einstein condensation of
excitons in a harmonic potential.Comment: 10 figures, 1 tabl
Effect of lubricants and sliding conditions on the tribo-performance of SiO2/epoxy composites
The influence of solid lubricants, normal load, sliding speed and water environment on the tribo-performance of solid lubricant-containing SiO2-epoxy composites is investigated. 10 to 15 wt% PTFE concentration yields a low coefficient of friction (CoF) and low wear rate under 60 N load. With increasing PTFE concentration in the composites, the load capacity decreases. Graphite exhibits worse friction and wear performance than PTFE under dry sliding condition, i.e. the CoF increases with a decreasing load in ball-on-disc. A higher concentration of PTFE-containing tribolayer on the worn composite surface is found under a higher load. The CoF and ball wear rate increase with increasing sliding speed under dry sliding, which is accompanied with an increase of the surface temperature of the composite. A high relative humidity is advantageous for a low friction due to adsorbed water molecules that lubricate the sliding couple. Water lubrication leads to a lower wear rate of the PTFE and graphite filled composites, whereas it gives rise to a higher wear rate of the Al2O3 ball due to the lack of protection of the transfer films
A spherical perfect lens
It has been recently proved that a slab of negative refractive index material
acts as a perfect lens in that it makes accessible the sub-wavelength image
information contained in the evanescent modes of a source. Here we elaborate on
perfect lens solutions to spherical shells of negative refractive material
where magnification of the near-field images becomes possible. The negative
refractive materials then need to be spatially dispersive with and . We concentrate on lens-like solutions for the
extreme near-field limit. Then the conditions for the TM and TE polarized modes
become independent of and respectively.Comment: Revtex4, 9 pages, 2 figures (eps
Ferromagnetic GaMnAs/GaAs superlattices - MBE growth and magnetic properties
We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices
with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML)
(23-45 \AA), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 \AA).
While previous reports state that GaMnAs layers thinner than 50 \AA are
paramagnetic in the whole Mn composition range achievable using MBE growth (up
to 8% Mn), we have found that short period superlattices exhibit a
paramagnetic-to-ferromagnetic phase transition with a transition temperature
which depends on both the thickness of the magnetic GaMnAs layer and the
nonmagnetic GaAs spacer. The neutron scattering experiments have shown that the
magnetic layers in superlattices are ferromagnetically coupled for both thin
(below 50 \AA) and thick (above 50 \AA) GaMnAs layers.Comment: Proceedings of 4th International Workshop on Molecular Beam Epitaxy
and Vapour Phase Epitaxy Growth Physics and Technology, September 23 - 28
(2001), Warszawa, Poland, to appear in Thin Solid Films. 24 pages, 8 figure
Sleep onset problems and subcortical development in infants later diagnosed with autism spectrum disorder
Objective: Sleep patterns in children with autism spectrum disorder (ASD) appear to diverge from typical development in the second or third year of life. Little is known, however, about the occurrence of sleep problems in infants who later develop ASD and possible effects on early brain development. In a longitudinal neuroimaging study of infants at familial high or low risk for ASD, parent-reported sleep onset problems were examined in relation to subcortical brain volumes in the first 2 years of life. Methods: A total of 432 infants were included across three study groups: infants at high risk who developed ASD (N=71), infants at high risk who did not develop ASD (N=234), and infants at low risk (N=127). Sleep onset problem scores (derived from an infant temperament measure) were evaluated in relation to longitudinal high-resolution T1 and T2 structural imaging data acquired at 6, 12, and 24 months of age. Results: Sleep onset problems were more common at 6–12 months among infants who later developed ASD. Infant sleep onset problems were related to hippocampal volume trajectories from 6 to 24 months only for infants at high risk who developed ASD. Brain-sleep relationships were specific to the hippocampus; no significant relationships were found with volume trajectories of other subcortical structures examined (the amygdala, caudate, globus pallidus, putamen, and thalamus). Conclusions: These findings provide initial evidence that sleep onset problems in the first year of life precede ASD diagnosis and are associated with altered neurodevelopmental trajectories in infants at high familial risk who go on to develop ASD. If replicated, these findings could provide new insights into a potential role of sleep difficulties in the development of ASD
Deflection and Rotation of CMEs from Active Region 11158
Between the 13 and 16 of February 2011 a series of coronal mass ejections
(CMEs) erupted from multiple polarity inversion lines within active region
11158. For seven of these CMEs we use the Graduated Cylindrical Shell (GCS)
flux rope model to determine the CME trajectory using both Solar Terrestrial
Relations Observatory (STEREO) extreme ultraviolet (EUV) and coronagraph
images. We then use the Forecasting a CME's Altered Trajectory (ForeCAT) model
for nonradial CME dynamics driven by magnetic forces, to simulate the
deflection and rotation of the seven CMEs. We find good agreement between the
ForeCAT results and the reconstructed CME positions and orientations. The CME
deflections range in magnitude between 10 degrees and 30 degrees. All CMEs
deflect to the north but we find variations in the direction of the
longitudinal deflection. The rotations range between 5\mydeg and 50\mydeg with
both clockwise and counterclockwise rotations occurring. Three of the CMEs
begin with initial positions within 2 degrees of one another. These three CMEs
all deflect primarily northward, with some minor eastward deflection, and
rotate counterclockwise. Their final positions and orientations, however,
respectively differ by 20 degrees and 30 degrees. This variation in deflection
and rotation results from differences in the CME expansion and radial
propagation close to the Sun, as well as the CME mass. Ultimately, only one of
these seven CMEs yielded discernible in situ signatures near Earth, despite the
active region facing near Earth throughout the eruptions. We suggest that the
differences in the deflection and rotation of the CMEs can explain whether each
CME impacted or missed the Earth.Comment: 18 pages, 6 figures, accepted in Solar Physic
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