Surface Grafting of Poly(L-glutamates). 3. Block Copolymerization

This paper describes for the first time the synthesis of surface-grafted AB-block copolypeptides, consisting of poly(γ-benzyl L-glutamate) (PBLG) as the A-block and poly(γ-methyl L-glutamate) (PMLG) as the B-block. Immobilized primary amine groups of (γ-aminopropyl)triethoxysilane (APS) on silicon wafers initiated the ring-opening polymerization of N-carboxyanhydrides of glutamic acid esters (NCAs). After removal of the BLG-NCA monomer solution after a certain reaction time, the amine end groups of the formed PBLG blocks acted as initiators for the second monomers. This method provides the possibility of making layered structures of surface-grafted block copolymers with tuned properties. Ellipsometry and small-angle X-ray reflection (SAXR) measurements revealed the thickness of the polypeptide layers ranging from 45-100 Å of the first block to 140-270 Å for the total block copolypeptides. The chemical composition of the blocks was determined by X-ray photoelectron spectroscopy (XPS). In addition, Fourier transform infrared transmission spectroscopy (FT-IR) revealed that the polypeptide main chains of both blocks consisted of pure R-helices. The average orientation of the helices ranging from 22-42° with respect to the substrate within the first block to 31-35° in the second block could be derived with FT-IR as well.

Probing the Magnetized Interstellar Medium Surrounding the Planetary Nebula Sh 2-216

We present 1420 MHz polarization images of a 2.5 X 2.5 degree region around the planetary nebula (PN) Sh 2-216. The images are taken from the Canadian Galactic Plane Survey (CGPS). An arc of low polarized intensity appears prominently in the north-east portion of the visible disk of Sh 2-216, coincident with the optically identified interaction region between the PN and the interstellar medium (ISM). The arc contains structural variations down to the ~1 arcminute resolution limit in both polarized intensity and polarization angle. Several polarization-angle "knots" appear along the arc. By comparison of the polarization angles at the centers of the knots and the mean polarization angle outside Sh 2-216, we estimate the rotation measure (RM) through the knots to be -43 +/- 10 rad/m^2. Using this estimate for the RM and an estimate of the electron density in the shell of Sh 2-216, we derive a line-of-sight magnetic field in the interaction region of 5.0 +/- 2.0 microG. We believe it more likely the observed magnetic field is interstellar than stellar, though we cannot completely dismiss the latter possibility. We interpret our observations via a simple model which describes the ISM magnetic field around Sh 2-216, and comment on the potential use of old PNe as probes of the magnetized ISM.Comment: 25 pages, 4 figures. Accepted for publication in the Astrophysical Journa

A Highly Ordered Faraday-Rotation Structure in the Interstellar Medium

We describe a Faraday-rotation structure in the Interstellar Medium detected through polarimetric imaging at 1420 MHz from the Canadian Galactic Plane Survey (CGPS). The structure, at l=91.8, b=-2.5, has an extent of ~2 degree, within which polarization angle varies smoothly over a range of ~100 degree. Polarized intensity also varies smoothly, showing a central peak within an outer shell. This region is in sharp contrast to its surroundings, where low-level chaotic polarization structure occurs on arcminute scales. The Faraday-rotation structure has no counterpart in radio total intensity, and is unrelated to known objects along the line of sight, which include a Lynds Bright Nebula, LBN 416, and the star cluster M39 (NGC7092). It is interpreted as a smooth enhancement of electron density. The absence of a counterpart, either in optical emission or in total intensity, establishes a lower limit to its distance. An upper limit is determined by the strong beam depolarization in this direction. At a probable distance of 350 +/- 50 pc, the size of the object is 10 pc, the enhancement of electron density is 1.7 cm-3, and the mass of ionized gas is 23 M_sun. It has a very smooth internal magnetic field of strength 3 microG, slightly enhanced above the ambient field. G91.8-2.5 is the second such object to be discovered in the CGPS, and it seems likely that such structures are common in the Magneto-Ionic Medium.Comment: 16 pages, 5 figures, ApJ accepte

What approaches are most effective at addressing micronutrient deficiency in children 0-5 years?:A review of systematic reviews

Introduction Even though micronutrient deficiency is still a major public health problem, it is still unclear which interventions are most effective in improving micronutrient status. This review therefore aims to summarize the evidence published in systematic reviews on intervention strategies that aim at improving micronutrient status in children under the age of five. Methods We searched the literature and included systematic reviews that reported on micronutrient status as a primary outcome for children of 0–5 years old, had a focus on low or middle income countries. Subsequently, papers were reviewed and selected by two authors. Results We included 4235 reviews in this systematic review. We found that (single or multiple) micronutrient deficiencies in pre-school children improved after providing (single or multiple) micronutrients. However home fortification did not always lead to significant increase in serum vitamin A, serum ferritin, hemoglobin or zinc. Commercial fortification did improve iron status. Cord clamping reduced the risk of anemia in infants up to 6 months and, in helminth endemic areas, anthelminthic treatment increased serum ferritin levels, hemoglobin and improved height for age z-scores. Anti-malaria treatment improved ferritin levels. Discussion Based on our results the clearest recommendations are: delayed cord clamping is an effective intervention for reducing anemia in early life. In helminth endemic areas iron status can be improved by anthelminthic treatment. Anti-malaria treatment can improve ferritin. In deficient populations, single iron, vitamin A and multimicronutrient supplementation can improve iron, vitamin A and multimicronutrient status respectively. While the impact of home-fortification on multimicronutrient status remains questionable, commercial iron fortification may improve iron status

Radio polarimetric imaging of the interstellar medium: magnetic field and diffuse ionized gas structure near the W3/W4/W5/HB3 complex

We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron background emission by Faraday rotation arising in foreground ionized gas having an emission measure as low as 1 cm^{-6} pc. Several new remarkable phenomena have been identified, including: mottled polarization arising from random fluctuations in a magneto-ionic screen that we identify with a medium in the Perseus Arm, probably in the vicinity of the HII regions themselves; depolarization arising from very high rotation measures (several times 10^3 rad m^{-2}) and rotation measure gradients due to the dense, turbulent environs of the HII regions; highly ordered features spanning up to several degrees; and an extended influence of the HII regions beyond the boundaries defined by earlier observations. In particular, the effects of an extended, low-density ionized halo around the HII region W4 are evident, probably an example of the extended HII envelopes postulated as the origin of weak recombination-line emission detected from the Galactic ridge. Our polarization observations can be understood if the uniform magnetic field component in this envelope scales with the square-root of electron density and is 20 microG at the edge of the depolarized region around W4, although this is probably an over-estimate since the random field component will have a significant effect.Comment: 18 pages, 8 figures (7 jpeg and 1 postscript), accepted for publication in the Astrophysical Journa

Surface Grafting of Poly(L-glutamates). 2. Helix Orientation

In this paper the average helix orientation of surface-grafted poly(γ-benzyl L-glutamate) (PBLG), poly(γ-methyl L-glutamate) (PMLG), and poly(γ-methyl L-glutamate)-co-(γ-n-stearyl L-glutamate) (PMLGSLG 70/30) was investigated by means of FT-IR transmission spectroscopy. The theoretical relation between the average tilt angle (θ) and the absorption peak areas of three different backbone amide bands could be calculated because their transition dipole moment directions with respect to the helix axis were known. From the normalized absorptions, the average tilt angles of grafted helices of PBLG, PMLG, and PMLGSLG 70/30 were determined. The somewhat larger average angle of PMLG helices of 35 ± 5° with respect to the substrate compared to the value of 32 ± 5° of PBLG was due to the higher grafting density of PMLG. Because of the smaller helix diameter as a result of the smaller size of the methyl side group, more PMLG helices grew on the same surface area. Sterical hindrance and unfavorable polar interactions between unidirectional aligned helices forced the PMLG helices in a more upright arrangement. The even more perpendicular orientation of PMLGSLG 70/30 (48 ± 6°) could be the result of incorporation of mainly γ-methyl L-glutamate N-carboxyanhydride (MLG-NCA) monomers during the initiation step. Incorporation of the much larger γ-n-stearyl L-glutamate N-carboxyanhydride (SLG-NCA) monomers afterward lead to enlarged angles with respect to the substrate. Due to swelling, a pronounced change in helix orientation of grafted PMLGSLG 70/30 in n-hexadecane was observed, resulting in an almost perpendicular helix orientation.

The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid

The Australian SKA Pathfinder (ASKAP) is being used to undertake a campaign to rapidly survey the sky in three frequency bands across its operational spectral range. The first pass of the Rapid ASKAP Continuum Survey (RACS) at 887.5 MHz in the low band has already been completed, with images, visibility datasets, and catalogues made available to the wider astronomical community through the CSIRO ASKAP Science Data Archive (CASDA). This work presents details of the second observing pass in the mid band at 1367.5 MHz, RACS-mid, and associated data release comprising images and visibility datasets covering the whole sky south of declination $+$49$^\circ$. This data release incorporates selective peeling to reduce artefacts around bright sources, as well as accurately modelled primary beam responses. The Stokes I images reach a median noise of 198 $\mu$Jy PSF$^{-1}$ with a declination-dependent angular resolution of 8.1 to 47.5 arcsec that fills a niche in the existing ecosystem of large-area astronomical surveys. We also supply Stokes V images after application of a widefield leakage correction, with a median noise of 165 $\mu$Jy PSF$^{-1}$. We find the residual leakage of Stokes I into V to be $\lesssim$ 0.9 to 2.4 % over the survey. This initial RACS-mid data release will be complemented by a future release comprising catalogues of the survey region. As with other RACS data releases, data products from this release will be made available through CASDA.Comment: 39 pages, 85 figure files, accepted for publication in PASA. For associated data see https://doi.org/10.25919/6mr6-rd8

Long-term spectral and timing properties of the soft gamma-ray repeater SGR 1833-0832 and detection of extended X-ray emission around the radio pulsar PSR B1830-08

SGR 1833-0832 was discovered on 2010 March 19 thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi X-ray Timing Explorer, and XMM-Newton. Using these data, which span about 225 days, we studied the long-term spectral and timing characteristics of SGR 1833-0832. We found evidence for diffuse emission surrounding SGR 1833-0832, which is most likely a halo produced by the scattering of the point source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT=1.2 keV and absorbing column nH=(10.4+/-0.2)E22 cm^-2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at about 3.7E-12 erg/cm^2/s for the first 20 days after the onset of the bursting episode, then it faded by a factor 40 in the subsequent 140 days, following a power-law trend with index alpha=-0.5. We obtained a phase-coherent timing solution with the longest baseline (225 days) to date for this source which, besides period P=7.5654084(4) s and period derivative dP/dt=3.5(3)E-12 s/s, includes higher order period derivatives. We also report on our search of the counterpart to the SGR at radio frequencies using the Australia Telescope Compact Array and the Parkes radio telescope. No evidence for radio emission was found, down to flux densities of 0.9 mJy (at 1.5 GHz) and 0.09 mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs.Comment: 12 pages, 7 colour figures and 3 tables, accepted for publication in MNRAS. Figure 6 in reduced quality and abstract abridged for astro-ph submissio

BeppoSAX Observations of GRB980425: Detection of the Prompt Event and Monitoring of the Error Box

We present BeppoSAX follow-up observations of GRB980425 obtained with the Narrow Field Instruments (NFI) in April, May, and November 1998. The first NFI observation has detected within the 8' radius error box of the GRB an X-ray source positionally consistent with the supernova 1998bw, which exploded within a day of GRB980425, and a fainter X-ray source, not consistent with the position of the supernova. The former source is detected in the following NFI pointings and exhibits a decline of a factor of two in six months. If it is associated with SN 1998bw, this is the first detection of X-ray emission from a Type I supernova above 2 keV. The latter source exhibits only marginally significant variability. The X-ray spectra and variability of the supernova are compared with thermal and non-thermal models of supernova high energy emission. Based on the BeppoSAX data, it is not possible to firmly establish which of the two detected sources is the GRB X-ray counterpart, although probability considerations favor the supernova.Comment: 16 pages, Latex, 6 PostScript figures and 1 GIF figure, 2 tables, submitted to The Astrophysical Journa

A Relativistic Type Ibc Supernova Without a Detected Gamma-ray Burst

Long duration gamma-ray bursts (GRBs) mark the explosive death of some massive stars and are a rare sub-class of Type Ibc supernovae (SNe Ibc). They are distinguished by the production of an energetic and collimated relativistic outflow powered by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested in the pulse of gamma-rays and a long-lived radio afterglow. To date, central engine-driven SNe have been discovered exclusively through their gamma-ray emission, yet it is expected that a larger population goes undetected due to limited satellite sensitivity or beaming of the collimated emission away from our line-of-sight. In this framework, the recovery of undetected GRBs may be possible through radio searches for SNe Ibc with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary Type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. The lack of a coincident GRB makes SN 2009bb the first engine-driven SN discovered without a detected gamma-ray signal. A comparison with our extensive radio survey of SNe Ibc reveals that the fraction harboring central engines is low, ~1 percent, measured independently from, but consistent with, the inferred rate of nearby GRBs. Our study demonstrates that upcoming optical and radio surveys will soon rival gamma-ray satellites in pinpointing the nearest engine-driven SNe. A similar result for a different supernova is reported independently.Comment: To appear in Nature on Jan 28 2010. Embargoed for discussion in the press until 13:00 US Eastern Time on Jan 27 (Accepted version, 27 pages, Manuscript and Suppl. Info.