Magnetic-Field Amplification in the Thin X-ray Rims of SN1006

Several young supernova remnants (SNRs), including SN1006, emit synchrotron X-rays in narrow filaments, hereafter thin rims, along their periphery. The widths of these rims imply 50 to 100 $\mu$G fields in the region immediately behind the shock, far larger than expected for the interstellar medium compressed by unmodified shocks, assuming electron radiative losses limit rim widths. However, magnetic-field damping could also produce thin rims. Here we review the literature on rim width calculations, summarizing the case for magnetic-field amplification. We extend these calculations to include an arbitrary power-law dependence of the diffusion coefficient on energy, $D \propto E^{\mu}$. Loss-limited rim widths should shrink with increasing photon energy, while magnetic-damping models predict widths almost independent of photon energy. We use these results to analyze Chandra observations of SN 1006, in particular the southwest limb. We parameterize the full widths at half maximum (FWHM) in terms of energy as FWHM $\propto E^{m_E}_{\gamma}$. Filament widths in SN1006 decrease with energy; $m_E \sim -0.3$ to $-0.8$, implying magnetic field amplification by factors of 10 to 50, above the factor of 4 expected in strong unmodified shocks. For SN 1006, the rapid shrinkage rules out magnetic damping models. It also favors short mean free paths (small diffusion coefficients) and strong dependence of $D$ on energy ($\mu \ge 1$).Comment: Accepted by ApJ, 49 pages, 10 figure

Strategies for Continued Successful Treatment in Patients with Alzheimer's Disease : An Overview of Switching Between Pharmacological Agents

Altres ajuts: This review article is sponsored by Novartis Pharma K.K., Tokyo, Japan. The publication processing fees were funded by Novartis Pharma K.K., Tokyo, Japan.Alzheimer's disease (AD) is the most common cause of dementia, characterized by a progressive decline in cognition and function. Current treatment options for AD include the cholines-terase inhibitors (ChEIs) donepezil, galantamine, and rivastigmine, as well as the N-methyl-D-aspartate receptor antagonist memantine. Treatment guidelines recommend the use of ChEIs as the standard of care first-line therapy. Several randomized clinical studies have demonstrated the benefits of ChEIs on cogni-tion, global function, behavior and activities of daily living. However, patients may fail to achieve sus-tained clinical benefits from ChEIs due to lack/loss of efficacy and/or safety, tolerability issues, and poor adherence to the treatment. The purpose of this review is to explore the strategies for continued successful treatment in patients with AD. Literature search was performed for articles published in PubMed and MEDLINE, using pre-specified search terms. Articles were critically evaluated for inclusion based on their titles, abstracts, and full text of the publication. The findings of this review indicate that dose up-titration and switching between ChEIs may help to improve response to ChEI treatment and also address issues such as lack/loss of effica-cy or safety/tolerability in patients with AD. However, well-designed studies are needed to provide robust evidence

Concert recording 2013-04-14a

[Track 01]. Moving air / Nigel Westlake -- [Track 02]. New York counterpoint / Steve Reich -- [Track 03]. In motion hand covers bruise / Trent Reznor ; Atticus Ross -- [Track 04]. When it rains / Brad Mehldau -- [Track 05]. Born to be wild / David Lang -- [Track 06]. Cheating, lying, stealing / David Lang -- [Track 07]. Two instrumental rounds in snaketime / Moondog -- [Track 08]. Motown metal / Michael Daughterty

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Dust Destruction in Type Ia Supernova Remnants in the Large Magellanic Cloud

We present first results from an extensive survey of Magellanic Clouds supernova remnants (SNRs) with the Spitzer Space Telescope. We describe IRAC and MIPS imaging observations at 3.6, 4.5, 5.8, 8, 24, and 70 microns of four Balmer-dominated Type Ia SNRs in the Large Magellanic Cloud (LMC): DEM L71 (0505-67.9), 0509--67.5, 0519--69.0, and 0548-70.4. None was detected in the four short-wavelength IRAC bands, but all four were clearly imaged at 24 microns, and two at 70 microns. A comparison of these images to Chandra broadband X-ray images shows a clear association with the blast wave, and not with internal X-ray emission associated with ejecta. Our observations are well described by 1-D shock models of collisionally heated dust emission, including grain size distributions appropriate for the LMC, grain heating by collisions with both ions and electrons, and sputtering of small grains. Model parameters are constrained by X-ray, optical, and far-ultraviolet observations. Our models can reproduce observed 70/24 micron flux ratios only by including sputtering, destroying most grains smaller than 0.03-0.04 microns in radius. We infer total dust masses swept up by the SNR blast waves, before sputtering, of order 0.01 solar masses, several times less than those implied by a dust/gas mass ratio of 0.3 percent as often assumed for the LMC. Substantial dust destruction has implications for gas-phase abundances.Comment: 11 pages, 1 figure, submitted to the Astrophysical Journal Letter