Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times

We present optical spectra of the nearby Type Ia supernova SN 2011fe at 100, 205, 311, 349, and 578 days post-maximum light, as well as an ultraviolet spectrum obtained with Hubble Space Telescope at 360 days post-maximum light. We compare these observations with synthetic spectra produced with the radiative transfer code PHOENIX. The day +100 spectrum can be well fit with models which neglect collisional and radiative data for forbidden lines. Curiously, including this data and recomputing the fit yields a quite similar spectrum, but with different combinations of lines forming some of the stronger features. At day +205 and later epochs, forbidden lines dominate much of the optical spectrum formation; however, our results indicate that recombination, not collisional excitation, is the most influential physical process driving spectrum formation at these late times. Consequently, our synthetic optical and UV spectra at all epochs presented here are formed almost exclusively through recombination-driven fluorescence. Furthermore, our models suggest that the ultraviolet spectrum even as late as day +360 is optically thick and consists of permitted lines from several iron-peak species. These results indicate that the transition to the "nebular" phase in Type Ia supernovae is complex and highly wavelength-dependent.Comment: 22 pages, 21 figuress, 1 table, submitted to MNRA

A Portable Chemotaxis Platform for Short and Long Term Analysis

Flow-based microfluidic systems have been widely utilized for cell migration studies given their ability to generate versatile and precisely defined chemical gradients and to permit direct visualization of migrating cells. Nonetheless, the general need for bulky peripherals such as mechanical pumps and tubing and the complicated setup procedures significantly limit the widespread use of these microfluidic systems for cell migration studies. Here we present a simple method to power microfluidic devices for chemotaxis assays using the commercially available ALZET® osmotic pumps. Specifically, we developed a standalone chemotaxis platform that has the same footprint as a multiwell plate and can generate well-defined, stable chemical gradients continuously for up to 7 days. Using this platform, we validated the short-term (24 hours) and long-term (72 hours) concentration dependent PDGF-BB chemotaxis response of human bone marrow derived mesenchymal stem cells.Harvard Stem Cell InstituteNational Institutes of Health (U.S.) (grant HL095722)National Institutes of Health (U.S.) (grant HL097172)Massachusetts Institute of Technology (MIT-UROP program)Massachusetts Institute of Technology (John Reed Fund)National Institute of Biomedical Imaging and Bioengineering (U.S.) (BioMEMS Resource Center (P41 EB 002503)

The Berkeley Sample of Stripped-Envelope Supernovae

We present the complete sample of stripped-envelope supernova (SN) spectra observed by the Lick Observatory Supernova Search (LOSS) collaboration over the last three decades: 888 spectra of 302 SNe, 652 published here for the first time, with 384 spectra (of 92 SNe) having photometrically-determined phases. After correcting for redshift and Milky Way dust reddening and reevaluating the spectroscopic classifications for each SN, we construct mean spectra of the three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We compare measures of line strengths and widths made from this sample to the results of previous efforts, confirming that O I {\lambda}7774 absorption is stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb SNe in the first 30 days after peak brightness, though the widths of nebular emission lines are consistent across subtypes. We also highlight newly available observations for a few rare subpopulations of interest.Comment: 13 pages; 14 figures; 3 tables. Accepted for publication in MNRA

Diagnostic and Prognostic Plasma Biomarkers for Idiopathic Pneumonia Syndrome after Hematopoietic Cell Transplantation

Idiopathic pneumonia syndrome (IPS) is a noninfectious pulmonary complication after hematopoietic cell transplantation (HCT) and is difficult to diagnose. In 41 patients with IPS, we evaluated 6 candidate proteins in plasma samples at day 7 post-HCT and at onset of IPS to identify potential diagnostic or prognostic biomarkers for IPS. Samples at similar times from 162 HCT recipients without documented infections and 37 HCT recipients with respiratory viral pneumonia served as controls. In multivariable models, a combination of Stimulation-2 (ST2; odds ratio [OR], 2.8; P < .001) and IL-6 (OR, 1.4; P = .025) was the best panel for distinguishing IPS at diagnosis from unaffected controls, whereas tumor necrosis factor receptor 1 (TNFR1; OR, 2.9; P = .002) was the best marker when comparing patients with IPS and viral pneumonia. The areas under the curve of the receiver operating characteristic (ROC) curves for discriminating between IPS and unaffected controls at day 7 post-HCT were .8 for ST2, .75 for IL-6, and .68 for TNFR1. Using estimated sensitivity and specificity values from cutoffs determined with the ROC analysis (cutoff level: ST2, 21 ng/mL; IL-6, 61 pg/mL; TNFR1, 3421 pg/mL), we calculated positive predictive values (PPV) for a range of estimated population prevalence values of IPS. Among the 3 markers, ST2 showed the highest PPV for IPS occurrence. Based on an assumed prevalence of 8%, a positive ST2 test increased likelihood of IPS to 50%. We conclude that a prospective validation study is warranted to determine whether a plasma biomarker panel can aid the noninvasive diagnosis and prognosis of IPS

Introduction : media and illiberal democracy in Central and Eastern Europe

This introductory overview opens the series of articles included in the issue entitled Media and Illiberal Democracy in Central and Eastern Europe, and sets the scene for the debate on the relationship between illiberal trends in politics and media landscapes in the region. Drawing on existing scholarship, it traces the roots and the evolution of illiberalism, focusing the discussion within the confines of particularities of media landscapes. Through the introduction of articles addressing manifestations of illiberalism in media landscapes, it argues that “illiberal turn” in Central and Eastern Europe is part of a global political shift, rather than a regional one

Reverberation Mapping of the Kepler-Field AGN KA1858+4850

KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m telescope from February to November of 2012, and obtained complementary V-band images from five other ground-based telescopes. We measured the H-beta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method, and found rest-frame lags of lag_CCF = 13.53 (+2.03, -2.32) days and lag_JAVELIN = 13.15 (+1.08, -1.00) days. The H-beta root-mean-square line profile has a width of sigma_line = 770 +/- 49 km/s. Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M_BH = 8.06 (+1.59, -1.72) x 10^6 M_sun for the mass of the central black hole and an Eddington ratio of L/L_Edd ~ 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei