Reading First Impact Study: Interim Report

This report, written by Abt Associates and MDRC and published by the U.S. Department of Education's Institute of Education Sciences, finds that Reading First increased the amount of time that teachers spent on the five essential components of reading instruction, as defined by the National Reading Panel. While Reading First did not improve students' reading comprehension on average, there are some indications that some sites had impacts on both instruction and reading comprehension. An overview puts these interim findings in context

The redshift determination of GRB 990506 and GRB 000418 with the Echellete Spectrograph Imager on Keck

Using the Echellete Spectrograph Imager (ESI) on the Keck II 10-m telescope we have measured the redshifts of the host galaxies of gamma-ray bursts GRB 990506 and GRB 000418, z=1.30658 +/- 0.00004 and 1.1181 +/- 0.0001, respectively. Thanks to the excellent spectral resolution of ESI we resolved the [O II] 3727 doublet in both cases. The measured redshift of GRB 990506 is the highest known for a dark burst GRB, though entirely consistent with the notion that dark and non-dark bursts have a common progenitor origin. The relative strengths of the [O II], He I, [Ne III], and H gamma emission lines suggest that the host of GRB 000418 is a starburst galaxy, rather than a LINER or Seyfert 2. Since the host of GRB 000418 has been detected at sub-millimeter wavelengths these spectroscopic observations suggest that the sub-millimeter emission is due to star-formation (as opposed to AGN) activity. The [O II]-derived unobscured star-formation rates are 13 and 55 M_solar/yr for the hosts of GRB 990506 and GRB 000418, respectively. In contrast, the star-formation rate of the host of GRB 000418 derived from sub-millimeter observations is twenty times larger.Comment: To appear in the Astronomical Journal (accepted 4 December 2002). 15 pages, 3 Postscript figure

The host of the SN-less GRB 060505 in high resolution

The spiral host galaxy of GRB 060505 at z=0.089 was the site of a puzzling long duration burst without an accompanying supernova. Studies of the burst environment by Th\"one et al. (2008) suggested that this GRB came from the collapse of a massive star and that the GRB site was a region with properties different from the rest of the galaxy. We reobserved the galaxy in high spatial resolution using the VIMOS integral-field unit (IFU) at the VLT with a spaxel size of 0.67 arcsec. Furthermore, we use long slit high resolution data from HIRES/Keck at two different slit positions covering the GRB site, the center of the galaxy and an HII region next to the GRB region. We compare the properties of different HII regions in the galaxy with the GRB site and study the global and local kinematic properties of this galaxy. The resolved data show that the GRB site has the lowest metallicity in the galaxy with around 1/3 Z_solar, but its specific SFR (SSFR) of 7.4 M_solar/yr/L/L* and age (determined by the Halpha EW) are similar to other HII regions in the host. The galaxy shows a gradient in metallicity and SSFR from the bulge to the outskirts as it is common for spiral galaxies. This gives further support to the theory that GRBs prefer regions of higher star-formation and lower metallicity, which, in S-type galaxies, are more easily found in the spiral arms than in the centre. Kinematic measurements of the galaxy do not show evidence for large perturbations but a minor merger in the past cannot be excluded. This study confirms the collapsar origin of GRB060505 but reveals that the properties of the HII region surrounding the GRB were not unique to that galaxy. Spatially resolved observations are key to know the implications and interpretations of unresolved GRB hosts observations at higher redshifts.Comment: 15 pages, 16 figures, 6 tables; resubmitted to MNRAS after minor revision

Probing electron acceleration and X-ray emission in laser-plasma accelerator

While laser-plasma accelerators have demonstrated a strong potential in the acceleration of electrons up to giga-electronvolt energies, few experimental tools for studying the acceleration physics have been developed. In this paper, we demonstrate a method for probing the acceleration process. A second laser beam, propagating perpendicular to the main beam is focused in the gas jet few nanosecond before the main beam creates the accelerating plasma wave. This second beam is intense enough to ionize the gas and form a density depletion which will locally inhibit the acceleration. The position of the density depletion is scanned along the interaction length to probe the electron injection and acceleration, and the betatron X-ray emission. To illustrate the potential of the method, the variation of the injection position with the plasma density is studied

A Powerful New Quantitative Genetics Platform, Combining Caenorhabditis elegans High-Throughput Fitness Assays with a Large Collection of Recombinant Strains.

The genetic variants underlying complex traits are often elusive even in powerful model organisms such as Caenorhabditis elegans with controlled genetic backgrounds and environmental conditions. Two major contributing factors are: (1) the lack of statistical power from measuring the phenotypes of small numbers of individuals, and (2) the use of phenotyping platforms that do not scale to hundreds of individuals and are prone to noisy measurements. Here, we generated a new resource of 359 recombinant inbred strains that augments the existing C. elegans N2xCB4856 recombinant inbred advanced intercross line population. This new strain collection removes variation in the neuropeptide receptor gene npr-1, known to have large physiological and behavioral effects on C. elegans and mitigates the hybrid strain incompatibility caused by zeel-1 and peel-1, allowing for identification of quantitative trait loci that otherwise would have been masked by those effects. Additionally, we optimized highly scalable and accurate high-throughput assays of fecundity and body size using the COPAS BIOSORT large particle nematode sorter. Using these assays, we identified quantitative trait loci involved in fecundity and growth under normal growth conditions and after exposure to the herbicide paraquat, including independent genetic loci that regulate different stages of larval growth. Our results offer a powerful platform for the discovery of the genetic variants that control differences in responses to drugs, other aqueous compounds, bacterial foods, and pathogenic stresses

Discovery of a supernova associated with GRB 031203: SMARTS Optical-Infrared Lightcurves from 0.2 to 92 days

Optical and infrared monitoring of the afterglow site of gamma-ray burst (GRB) 031203 has revealed a brightening source embedded in the host galaxy, which we attribute to the presence of a supernova (SN) related to the GRB ("SN 031203"). We present details of the discovery and evolution of SN 031203 from 0.2 to 92 days after the GRB, derived from SMARTS consortium photometry in I and J bands. A template type Ic lightcurve, constructed from SN 1998bw photometry, is consistent with the peak brightness of SN 031203 although the lightcurves are not identical. Differential astrometry reveals that the SN, and hence the GRB, occurred less than 300 h_71^-1 pc (3-sigma) from the apparent galaxy center. The peak of the supernova is brighter than the optical afterglow suggesting that this source is intermediate between a strong GRB and a supernova.Comment: 11 pages, 3 figures, submitted to ApJ Letter

Tuning the electron energy by controlling the density perturbation position in laser plasma accelerators

A density perturbation produced in an underdense plasma was used to improve the quality of electron bunches produced in the laser-plasma wakefield acceleration scheme. Quasi-monoenergetic electrons were generated by controlled injection in the longitudinal density gradients of the density perturbation. By tuning the position of the density perturbation along the laser propagation axis, a fine control of the electron energy from a mean value of 60 MeV to 120 MeV has been demonstrated with a relative energy-spread of 15 +/- 3.6%, divergence of 4 +/- 0.8 mrad and charge of 6 +/- 1.8 pC.Comment: 7 pages, 8 figure