Limits on radio emission from pulsar wind nebulae

We report on a sensitive survey for radio pulsar wind nebulae (PWN) towards 27 energetic and/or high velocity pulsars. Observations were carried out at 1.4 GHz using the Very Large Array and the Australia Telescope Compact Array, and utilised pulsar-gating to search for off-pulse emission. These observing parameters resulted in a considerably more sensitive search than previous surveys, and could detect PWN over a much wider range of spatial scales (and hence ambient densities and pulsar velocities). However, no emission clearly corresponding to a PWN was discovered. Based on these non-detections we argue that the young and energetic pulsars in our sample have winds typical of young pulsars, but produce unobservable PWN because they reside in low density (n approx 0.003 cm^-3) regions of the ISM. However, non-detections of PWN around older and less energetic pulsars can only be explained if the radio luminosity of their winds is less than 1e-5 of their spin-down luminosity, implying an efficiency at least an order of magnitude smaller than that seen for young pulsars.Comment: 9 pages, 3 embedded EPS files. Accepted to MNRA

Technology Competency Within The Non-Traditional Preservice Teacher Candidate Population: Survey Results

This study utilized action research with quantitative data analysis to investigate the personal technological skills and use of web-based applications of nontraditional teacher candidates enrolled in elementary education courses at a Historically Black College/University (HBCU) in the southeastern section of the USA. The goal was to gain a better understanding of the technological challenges encountered by non-traditional candidates and to determine how technology can inform instructional delivery of curriculum to improve this population’s representation, expression, and engagement of learning outcomes. Data were collected through an anonymous electronic survey distributed to each student enrolled in the elementary education courses. A total of 320 students were enrolled, 148 respondents participated in the survey to equal 46% (N = 148) of the elementary education teacher candidate population. Of the 148 participants, 109 classified themselves age 24 and older; for the purposes of this study, this group is defined as nontraditional teacher candidates. The results revealed that (a) the H0 was rejected for seven of the eight tested categories, therefore strengthening the HA; (b) 50% of teacher candidates, whether traditional or nontraditional, self-reported in the Learner to Basic levels category; (c) 47% of traditional and non-traditional candidates reported Proficient to Advanced level, thereby strengthening the alternative hypothesis. These findings are compelling and led to the development of a new conceptual framework, the Teacher Education Technology and Web-Based Application Survey (TETWAS), which proposes that faculty in an elementary preparatory program could promote and enhance the learning experiences of candidates

Investigation, testing, and development of an electron-bombardment ion engine system final report, mar. 3 - dec. 14, 1964

Electron bombardment, mercury-fueled ion engine system - investigation, testing, and development progra

A Broadband Study of the Emission from the Composite Supernova Remnant MSH 11-62

MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and X-ray observations have identified the remnant shell as well as its central pulsar wind nebula. The observations suggest a relatively young system expanding into a low density region. Here we present a study of MSH 11-62 using observations with the Chandra, XMM-Newton, and Fermi observatories, along with radio observations from the Australia Telescope Compact Array (ATCA). We identify a compact X-ray source that appears to be the putative pulsar that powers the nebula, and show that the X-ray spectrum of the nebula bears the signature of synchrotron losses as particles diffuse into the outer nebula. Using data from the Fermi LAT, we identify gamma-ray emission originating from MSH 11-62. With density constraints from the new X-ray measurements of the remnant, we model the evolution of the composite system in order to constrain the properties of the underlying pulsar and the origin of the gamma-ray emission.Comment: 12 Pages, 12 figures. Accepted for publication in the Astrophysical Journa

Statistical properties of giant pulses from the Crab pulsar

We have studied the statistics of giant pulses from the Crab pulsar for the first time with particular reference to their widths. We have analyzed data collected during 3.5 hours of observations conducted with the Westerbork Synthesis Radio Telescope operated in a tied-array mode at a frequency of 1200 MHz. The PuMa pulsar backend provided voltage recording of X and Y linear polarization states in two conjugate 10 MHz bands. We restricted the time resolution to 4 microseconds to match the scattering on the interstellar inhomogeneities. In total about 18000 giant pulses (GP) were detected in full intensity with a threshold level of 6 sigma. Cumulative probability distributions (CPD) of giant pulse energies were analyzed for groups of GPs with different effective widths in the range 4 to 65 microseconds. The CPDs were found to manifest notable differences for the different GP width groups. The slope of a power-law fit to the high-energy portion of the CPDs evolves from -1.7 to -3.2 when going from the shortest to the longest GPs. There are breaks in the CPD power-law fits indicating flattening at low energies with indices varying from -1.0 to -1.9 for the short and long GPs respectively. The GPs with a stronger peak flux density were found to be of shorter duration. We compare our results with previously published data and discuss the importance of these peculiarities in the statistical properties of GPs for the heoretical understanding of the emission mechanism responsible for GP generation.Comment: 5 pages, 2 figures. Accepted by Astronomy and Astrophysic

Physical Acoustics

Contains reports on four research projects.United States Navy, Office of Naval Research (Contract Nonr-1841(42))National Aeronautics and Space Administration (Contract NAw-6516

Galaxy And Mass Assembly (GAMA): growing up in a bad neighbourhood - how do low-mass galaxies become passive?

Both theoretical predictions and observations of the very nearby Universe suggest that low-mass galaxies (log$_{10}$[M$_{*}$/M$_{\odot}$]<9.5) are likely to remain star-forming unless they are affected by their local environment. To test this premise, we compare and contrast the local environment of both passive and star-forming galaxies as a function of stellar mass, using the Galaxy and Mass Assembly survey. We find that passive fractions are higher in both interacting pair and group galaxies than the field at all stellar masses, and that this effect is most apparent in the lowest mass galaxies. We also find that essentially all passive log$_{10}$[M$_{*}$/M$_{\odot}$]<8.5 galaxies are found in pair/group environments, suggesting that local interactions with a more massive neighbour cause them to cease forming new stars. We find that the effects of immediate environment (local galaxy-galaxy interactions) in forming passive systems increases with decreasing stellar mass, and highlight that this is potentially due to increasing interaction timescales giving sufficient time for the galaxy to become passive via starvation. We then present a simplistic model to test this premise, and show that given our speculative assumptions, it is consistent with our observed results.Comment: 20 pages, 12 figures, Accepted to MNRA

A multi-wavelength study of the radio source G296.7-0.9: confirmation as a Galactic supernova remnant

We present a multi-wavelength study of the radio source G296.7-0.9. This source has a bilateral radio morphology, a radio spectral index of -0.5 +/- 0.1, sparse patches of linear polarisation, and thermal X-rays with a bright arc near the radio boundary. Considering these characteristics, we conclude that G296.7-0.9 is a supernova remnant (SNR). The age and morphology of the SNR in the context of its environment suggest that the source is co-located with an HII region, and that portions of the shock front have broken out into a lower density medium. We see no evidence for a neutron star or pulsar wind nebula associated with SNR G296.7-0.9.Comment: 11 pages with 9 figures and 2 tables. Accepted for publication in MNRA

The SAMI Galaxy Survey: Gas Streaming and Dynamical M/L in Rotationally Supported Systems

Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the SAMI Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric Diskfit fits out to $r\sim2r_e$. For 12/14 with measured H I profiles, ionized gas and H I maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial starlight profile as nested, very flattened mass homeoids viewed as a S\'ersic form. Fitting broad-band SEDs to SDSS images gave median stellar mass/light 1.7 assuming a Kroupa IMF vs. 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM distributed similarly across the SAMI aperture that came to dominate motions as the starlight CSC declined rapidly. The rest had mass distributed differently from starlight. Subtracting fits of S\'ersic profiles to 13 VIKING Z-band images revealed residual weak bars. Near the bar PA, we assessed m = 2 streaming velocities, and found deviations usually <30 km/s from the CSC; three showed no deviation. Thus, asymmetries rarely influenced our CSCs despite co-located shock-indicating, emission-line flux ratios in more than 2/3.Comment: 21 pages, 15 figures. Accepted to MNRA

Derivation and long-term expansion of human endometrial and decidual organoids

This protocol describes the derivation and long-term culture of self-organising, 3D epithelial organoids from human uterine tissues. Organoids which recapitulate features of uterine glands in vivo can be derived from both non-pregnant endometrium and from the decidua of early pregnancy using the method described. The organoids are able to respond to hormonal signals, secrete components of uterine ‘milk’ and can also differentiate into ciliated luminal epithelial cells. Since implantation in vivo occurs onto the uterine ciliated luminal epithelium and since uterine glands are the major source of histotrophic nutrition for the developing human conceptus the organoids will allow studies of early implantation in vitro. In addition they provide a useful tool to study the role of uterine stem cells in cyclical endometrial breakdown, repair, hyperplasia, carcinoma and endometriosis. Organoids can be consistently established within one to two weeks of initiation of culture and can be expanded long term, cryopreserved and resurrected.This work was supported by Medical Research Council (MR/L020041/1), Centre for Trophoblast Research, University of Cambridge and Wellcome Trust (RG60992). M.Y.T. has received funding from E.U. 7th Framework Programme for research, technological development and demonstration under grant agreement no PIEF-GA-2013-629785. J.H. was supported by Wellcome Trust vacation scholarship. B-K. Koo is supported by a Sir Henry Dale Fellowship from the Wellcome Trust and the Royal Society [101241/Z/13/Z] and receives core support grant from the Wellcome Trust and MRC to the WT-MRC Cambridge Stem Cell Institute