375 research outputs found
Ionization of Infalling Gas
H-alpha emission from neutral halo clouds probes the radiation and
hydrodynamic conditions in the halo. Armed with such measurements, we can
explore how radiation escapes from the Galactic plane and how infalling gas can
survive a trip through the halo. The Wisconsin H-Alpha Mapper (WHAM) is one of
the most sensitive instruments for detecting and mapping optical emission from
the ISM. Here, we present recent results exploring the ionization of two
infallling high-velocity complexes. First, we report on our progress mapping
H-alpha emission covering the full extent of Complex A. Intensities are faint
(<100 mR; EM <0.2 pc cm^-6 but correlate on the sky and in velocity with 21-cm
emission. Second, we explore the ionized component of some Anti-Center Complex
clouds studied by Peek et al. (2007) that show dynamic shaping from interaction
with the Galactic halo.Comment: 4 pages, 2 figures; to appear in proceedings of "The Role of
Disk-Halo Interaction in Galaxy Evolution: Outflow vs Infall?" held in
Espinho, Portugal during 2008 Augus
Combined EEG-fMRI and tractography to visualise propagation of epileptic activity
In a patient with refractory temporal lobe epilepsy, EEG-fMRI showed activation in association with left anterior temporal interictal discharges, in the left temporal, parietal and occipital lobes. Dynamic causal modelling suggested propagation of neural activity from the temporal focus to the area of occipital activation. Tractography showed connections from the site of temporal lobe activation to the site of occipital activation. This demonstrates the principle of combining EEG-fMRI and tractography to delineate the pathways of propagation of epileptic activity
Quantum field dynamics of the slow rollover in the linear delta expansion
We show how the linear delta expansion, as applied to the slow-roll
transition in quantum mechanics, can be recast in the closed time-path
formalism. This results in simpler, explicit expressions than were obtained in
the Schr\"odinger formulation and allows for a straightforward generalization
to higher dimensions. Motivated by the success of the method in the
quantum-mechanical problem, where it has been shown to give more accurate
results for longer than existing alternatives, we apply the linear delta
expansion to four-dimensional field theory.
At small times all methods agree. At later times, the first-order linear
delta expansion is consistently higher that Hartree-Fock, but does not show any
sign of a turnover. A turnover emerges in second-order of the method, but the
value of at the
turnover. In subsequent applications of the method we hope to implement the
calculation in the context of an expanding universe, following the line of
earlier calculations by Boyanovsky {\sl et al.}, who used the Hartree-Fock and
large-N methods. It seems clear, however, that the method will become
unreliable as the system enters the reheating stage.Comment: 17 pages, 9 figures, revised version with extra section 4.2 including
second order calculatio
Growing Income Inequality Threatens American Education
The first of two articles in consecutive months describes the origins and nature of growing income inequality, and some of its consequences for American children. It documents the increased family income inequality that's occurred over the past 40 years and shows that the increased income disparity has been more than matched by an expanding gap between the amounts of money that low- and high-income parents spend on enrichment activities for their children. It also shows that the growth in income inequality has been accompanied by increasing gaps in academic achievement. The article draws from the first part of the author's recent book, Restoring Opportunity: The Crisis of Inequality and the Challenge for American Education (Harvard Education Press and the Russell Sage Foundation, 2014). The second part to the series, also drawn from Restoring Opportunity, describes ideas based on proven policy approaches that will enable the country to make progress on the enormous task of restoring the educational opportunities that children from low-income families need if they are to lead productive and fulfilling lives. © 2014
Improved perturbation theory in the vortex liquids state of type II superconductors
We develop an optimized perturbation theory for the Ginzburg - Landau
description of thermal fluctuations effects in the vortex liquids. Unlike the
high temperature expansion which is asymptotic, the optimized expansion is
convergent. Radius of convergence on the lowest Landau level is in
2D and in 3D. It allows a systematic calculation of magnetization
and specific heat contributions due to thermal fluctuations of vortices in
strongly type II superconductors to a very high precision. The results are in
good agreement with existing Monte Carlo simulations and experiments.
Limitations of various nonperturbative and phenomenological approaches are
noted. In particular we show that there is no exact intersection point of the
magnetization curves both in 2D and 3D.Comment: 24 pages, 9 figure
Traumatic Meniscal Tears Are Associated With Meniscal Degeneration
Background: Meniscal tears are traditionally classified into traumatic versus degenerative tears. Although this classification plays a major role in clinical decision making, no consensus exists on the exact definition of a traumatic or degenerative tear, and the histopathological basis for thi
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Cannabidivarin is anticonvulsant in mouse and rat in vitro and in seizure models
Summary
Background and purpose: Phytocannabinoids in Cannabis sativa have diverse
pharmacological targets extending beyond cannabinoid receptors and several exert notable
anticonvulsant effects. For the first time, we investigated the anticonvulsant profile of the
phytocannabinoid cannabidivarin (CBDV) in vitro and in in vivo seizure models.
Experimental approach: The effect of CBDV (1-100μM) on epileptiform local field
potentials (LFPs) induced in rat hippocampal brain slices by 4-AP application or Mg2+-free
conditions was assessed by in vitro multi-electrode array recordings. Additionally, the
anticonvulsant profile of CBDV (50-200 mg kg-1) in vivo was investigated in four rodent
seizure models: maximal electroshock (mES) and audiogenic seizures in mice, and
pentylenetetrazole (PTZ) and pilocarpine-induced seizures in rat. CBDV effects in
combination with commonly-used antiepileptic drugs were investigated in rat seizures.
Finally, the motor side effect profile of CBDV was investigated using static beam and gripstrength
assays.
Key results: CDBV significantly attenuated status epilepticus-like epileptiform LFPs
induced by 4-AP and Mg2+-free conditions. CBDV had significant anticonvulsant effects in
mES (≥100 mg kg-1), audiogenic (≥50 mg kg-1) and PTZ-induced seizures (≥100 mg kg-1).
CBDV alone had no effect against pilocarpine-induced seizures, but significantly attenuated
these seizures when administered with valproate or phenobarbital at 200 mg kg-1 CBDV.
CBDV had no effect on motor function.
Conclusions and Implications: These results indicate that CBDV is an effective
anticonvulsant across a broad range of seizure models, does not significantly affect normal
motor function and therefore merits further investigation in chronic epilepsy models to justify
human trials
Possibility of quantitative T2-mapping MRI of cartilage near metal in high tibial osteotomy: A human cadaver study
T2-mapping is a widely used quantitative MRI technique in osteoarthritis research. An important challenge for its application in the context of high tibial osteotomy (HTO) is the presence of metallic fixation devices. In this study, we evaluated the possibility of performing T2-mapping after a HTO, by assessing the extent of magnetic susceptibility artifacts and the influence on T2 relaxation times caused by two commonly used fixation devices. T2-mapping with a 3D fast spin-echo sequence at three Tesla was performed on 11 human cadaveric knee joints before and after implantation of a titanium plate and screws (n = 5) or cobalt chrome staples (n = 6). Mean T2 relaxation times were calculated in six cartila
Flavor changing Z-decays from scalar interactions at a Giga-Z Linear Collider
The flavor changing decay Z -> d_I \bar{d}_J is investigated with special
emphasis on the b \bar{s} final state. Various models for flavor violation are
considered: two Higgs doublet models (2HDM's), supersymmetry (SUSY) with flavor
violation in the up and down-type squark mass matrices and SUSY with flavor
violation mediated by R-parity-violating interaction. We find that, within the
SUSY scenarios for flavor violation, the branching ratio for the decay Z -> b
\bar{s} can reach 10^{-6} for large \tan\beta values, while the typical size
for this branching ratio in the 2HDM's considered is about two orders of
magnitudes smaller at best. Thus, flavor changing SUSY signatures in radiative
Z decays such as Z -> b \bar{s} may be accessible to future ``Z factories''
such as a Giga-Z version of the TESLA design.Comment: 27 pages, 15 figures, REVTeX4. A new section added and a few minor
corrections were made in the tex
Heavy-Higgs Lifetime at Two Loops
The Standard-Model Higgs boson with mass decays almost
exclusively to pairs of and bosons. We calculate the dominant two-loop
corrections of to the partial widths of these decays. In
the on-mass-shell renormalization scheme, the correction factor is found to be
, where the second term is the
one-loop correction. We give full analytic results for all divergent two-loop
Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to
high precision using numerical techniques. We find agreement with a previous
numerical analysis. The above correction factor is also in line with a recent
lattice calculation.Comment: 26 pages, 6 postscript figures. The complete paper including figures
is also available via WWW at
http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-247-96.ps.g
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