11,641 research outputs found
Morphological evolution of a 3D CME cloud reconstructed from three viewpoints
The propagation properties of coronal mass ejections (CMEs) are crucial to
predict its geomagnetic effect. A newly developed three dimensional (3D) mask
fitting reconstruction method using coronagraph images from three viewpoints
has been described and applied to the CME ejected on August 7, 2010. The CME's
3D localisation, real shape and morphological evolution are presented. Due to
its interaction with the ambient solar wind, the morphology of this CME changed
significantly in the early phase of evolution. Two hours after its initiation,
it was expanding almost self-similarly. CME's 3D localisation is quite helpful
to link remote sensing observations to in situ measurements. The investigated
CME was propagating to Venus with its flank just touching STEREO B. Its
corresponding ICME in the interplanetary space shows a possible signature of a
magnetic cloud with a preceding shock in VEX observations, while from STEREO B
only a shock is observed. We have calculated three principle axes for the
reconstructed 3D CME cloud. The orientation of the major axis is in general
consistent with the orientation of a filament (polarity inversion line)
observed by SDO/AIA and SDO/HMI. The flux rope axis derived by the MVA analysis
from VEX indicates a radial-directed axis orientation. It might be that locally
only the leg of the flux rope passed through VEX. The height and speed profiles
from the Sun to Venus are obtained. We find that the CME speed possibly had
been adjusted to the speed of the ambient solar wind flow after leaving COR2
field of view and before arriving Venus. A southward deflection of the CME from
the source region is found from the trajectory of the CME geometric center. We
attribute it to the influence of the coronal hole where the fast solar wind
emanated from.Comment: ApJ, accepte
Positive exchange bias in ferromagnetic La0.67Sr0.33MnO3 / SrRuO3 bilayers
Epitaxial La0.67Sr0.33MnO3 (LSMO)/ SrRuO3 (SRO) ferromagnetic bilayers have
been grown on (001) SrTiO3 (STO) substrates by pulsed laser deposition with
atomic layer control. We observe a shift in the magnetic hysteresis loop of the
LSMO layer in the same direction as the applied biasing field (positive
exchange bias). The effect is not present above the Curie temperature of the
SRO layer (), and its magnitude increases rapidly as the temperature is lowered
below . The direction of the shift is consistent with an antiferromagnetic
exchange coupling between the ferromagnetic LSMO layer and the ferromagnetic
SRO layer. We propose that atomic layer charge transfer modifies the electronic
state at the interface, resulting in the observed antiferromagnetic interfacial
exchange coupling.Comment: accepted to Applied Physics Letter
Search for and strangeonium-like structures
Theoretically, it has been presumed from an effective Lagrangian calculation
that there could exist two charged strangeonium-like molecular states
and , with and
configurations respectively. In the framework of QCD sum rules, we predict that
masses of () and ()
are and respectively, which are both above
their respective two meson thresholds. We suggest to put in practice the search
for these two charged strangeonium-like structures in future experiments.Comment: 7 pages, 4 eps figures; the version accepted for publication in PRD.
arXiv admin note: text overlap with arXiv:1203.070
Analysis of polybrominated diphenyl ether and tetrabromobisphenol A in plastic samples in Mongolia
This study was conducted to determine brominated flame retardants (BFRs) in electronic products in view compliance with the Restriction of Hazardous Substances (RoHS) and initiated by activities for implementation of the Stockholm Convention. Brominated flame retardants (BFRs) are synthetic additives mainly used in electrical and electronic appliances and in construction materials. Total 16 plastic casing samples were tested for threshold levels of polybrominated ethers. According the XFR results, the concentration of cadmium, lead, mercury and chromium were found below than Maximum Concentration Value (MCV) of RoHS, while the concentration of total bromine was exceeded the standard limitations in the samples. Only 1 out of the 16 plastic samples contains DecaBDEs while Tetrabromobisphenol (TBBP-A) is the major brominated flame retardants. However by the presence of one sample the average concentration of DecaBDE was above the RoHS limit of 1000 ppm as found in studies in other countries.DOI: http://doi.dx.org/10.5564/mjc.v15i0.317 Mongolian Journal of Chemistry 15 (41), 2014, p27-3
On the low energy properies of fermions with singular interactions
We calculate the fermion Green function and particle-hole susceptibilities
for a degenerate two-dimensional fermion system with a singular gauge
interaction. We show that this is a strong coupling problem, with no small
parameter other than the fermion spin degeneracy, N. We consider two
interactions, one arising in the context of the model and the other in
the theory of half-filled Landau level. For the fermion self energy we show in
contrast to previous claims that the qualitative behavior found in the leading
order of perturbation theory is preserved to all orders in the interaction. The
susceptibility at a general wavevector retains
the fermi-liquid form. However the susceptibility either
diverges as or remains finite but with nonanalytic wavevector,
frequency and temperature dependence. We express our results in the language of
recently discussed scaling theories, give the fixed-point action, and show that
at this fixed point the fermion-gauge-field interaction is marginal in ,
but irrelevant at low energies in .Comment: 21 pages, uuencoded LATEX file with included Postscript figures, R
Longitudinal imaging of microvascular remodelling in proliferative diabetic retinopathy using adaptive optics scanning light ophthalmoscopy
Purpose
To characterise longitudinal changes in the retinal microvasculature of type 2 diabetes mellitus (T2DM) as exemplified in a patient with proliferative diabetic retinopathy (PDR) using an adaptive optics scanning light ophthalmoscope (AOSLO).
Methods
A 35-year-old T2DM patient with PDR treated with scatter pan-retinal photocoagulation at the inferior retina 1 day prior to initial AOSLO imaging along with a 24-year-old healthy control were imaged in this study. AOSLO vascular structural and perfusion maps were acquired at four visits over a 20-week period. Capillary diameter and microaneurysm area changes were measured on the AOSLO structural maps. Imaging repeatability was established using longitudinal imaging of microvasculature in the healthy control.
Results
Capillary occlusion and recanalisation, capillary dilatation, resolution of local retinal haemorrhage, capillary hairpin formation, capillary bend formation, microaneurysm formation, progression and regression were documented over time in a region 2° superior to the fovea in the PDR patient. An identical microvascular network with same capillary diameter was observed in the control subject over time.
Conclusions
High-resolution serial AOSLO imaging enables in vivo observation of vasculopathic changes seen in diabetes mellitus. The implications of this methodology are significant, providing the opportunity for studying the dynamics of the pathological process, as well as the possibility of identifying highly sensitive and non-invasive biomarkers of end organ damage and response to treatment
Anything You Can Do, You Can Do Better: Neural Substrates of Incentive-Based Performance Enhancement
Performance-based pay schemes in many organizations share the fundamental assumption that the performance level for a given task will increase as a function of the amount of incentive provided. Consistent with this notion, psychological studies have demonstrated that expectations of reward can improve performance on a plethora of different cognitive and physical tasks, ranging from problem solving to the voluntary regulation of heart rate. However, much less is understood about the neural mechanisms of incentivized performance enhancement. In particular, it is still an open question how brain areas that encode expectations about reward are able to translate incentives into improved performance across fundamentally different cognitive and physical task requirements
Theory for Gossamer and Resonating Valence Bond Superconductivity
We use an effective Hamiltonian for two-dimensional Hubbard model including
an antiferromagnetic spin-spin coupling term to study recently proposed
gossamer superconductivity. We formulate a renormalized mean field theory to
approximately take into account the strong correlation effect in the partially
projected Gutzwiller wavefucntions. At the half filled, there is a first order
phase transition to separate a Mott insulator at large Coulomb repulsion U from
a gossamer superconductor at small U. Away from the half filled,the Mott
insulator is evolved into an resonating valence bond state, which is
adiabatically connected to the gossamer superconductor.Comment: 10 pages, 13 figure
Non-Fermi Liquid Behavior In Quantum Critical Systems
The problem of an electron gas interacting via exchanging transverse gauge
bosons is studied using the renormalization group method. The long wavelength
behavior of the gauge field is shown to be in the Gaussian universality class
with a dynamical exponent in dimensions .
This implies that the gauge coupling constant is exactly marginal. Scattering
of the electrons by the gauge mode leads to non-Fermi liquid behavior in . The asymptotic electron and gauge Green's functions, interaction
vertex, specific heat and resistivity are presented.Comment: 9 pages in REVTEX 2.0. Submitted to Phys. Rev. Lett. 3 figures in
postscript files can be obtained at [email protected]. The filename is
gan.figures.tar.z and it's compressed. You can uncompress it by using
commands: "uncompress gan.figures.tar.z" and "tar xvf gan.figures.tar
Energy Calibration of the JLab Bremsstrahlung Tagging System
In this report, we present the energy calibration of the Hall B
bremsstrahlung tagging system at the Thomas Jefferson National Accelerator
Facility. The calibration was performed using a magnetic pair spectrometer. The
tagged photon energy spectrum was measured in coincidence with pairs
as a function of the pair spectrometer magnetic field. Taking advantage of the
internal linearity of the pair spectrometer, the energy of the tagging system
was calibrated at the level of . The absolute energy scale
was determined using the rate measurements close to the end-point of
the photon spectrum. The energy variations across the full tagging range were
found to be MeV.Comment: 15 pages, 12 figure
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