18,735 research outputs found
[Letter from Alex Bradford to Lieutenant and Mrs. Ray Starner - November 4, 1940]
No full textLetter from Alex Bradford to Lieutenant and Mrs. Ray Starner describing the the current state of affairs that the author was experiencing, including: the London blitz, the moral of the troops on the ground, and the collective company of men opposing the Nazi regime
The student's guide to completing an author study
No full textThe 'Student's guide to completing an author study' emerged during the early development of the school library resource center program at Glen Stewart Elementary School in Stratford Canada on Prince Edward Island. This research process centered on an author study, with direct teaching and clear assignment. The resulting model has been adapted to various grade levels and subject areas in different schools.Source type: Electronic(1)http://proquest.umi.com/pqdweb?did=49237063&Fmt=7&clientId=65345&RQT=309&VName=PQ
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
The development of X-ray excited optical luminescence (XEOL) spectroscopic techniques for mineralogical and petrological applications
No full textThis thesis investigates the use of X-ray Excited Optical Luminescence (XEOL) and Time
Resolved X-ray Excited Optical Luminescence (TR XEOL) within the Earth sciences. The
project contains two primary objectives, the first of which is the design and building of a high-resolution luminescence spectroscopy facility. This includes the installation and
commissioning of the facility on the I18 microfocus beamline at Diamond, the UK's
national synchrotron facility. In describing the system's design and commissioning, I
explore many implications of the technique.
The second objective is using this new facility to investigate a suite of minerals to develop new analytical techniques utilizing XEOL and TR XEOL spectroscopy for
applications within the Earth sciences. An aspect of this investigation is to explore the potential of Time Resolved Optically Derived X-ray Absorption Spectroscopy (TR OD XAS) of substitute trace elements in minerals. To date CW OD XAS has been shown to have very limited application within the Earth sciences. (Soderholm et al., 1998-120) The thesis explores differences between photoluminescence (PL) and XEOL responses in
mineral systems, and investigates how these differences can be exploited.
Luminescence, the phenomenon upon which the thesis is based, is a complex and poorly
utilised phenomena within Earth sciences, it is however, orders of magnitude more
sensitive, than many of the more accepted techniques used for the detection of trace
elements, on this basis alone I would suggest it deserves further consideration.
Luminescence techniques have developed much further in other disciplines; I therefore
have incorporated many descriptions, models, and interpretations from other disciplines in order to identify methodologies and techniques that have the potential to be utilized in the study and interpretation of luminescence within the Earth sciences.
The thesis demonstrates that luminescence in minerals with measured lifetimes, as fast
as ~ 20 ps exist. Previously the recorded luminescent lifetimes, for minerals, in the
literature are measured in ns. This finding leads to the novel concept that the
measurement of TR XEOL with ps resolution combined with the measurement of the
intensity of a luminescent signal as a function of excitation can provide significant new insights into the nature of the emission and the luminescent processes. I explore and demonstrate the potential of using dose dependence techniques of continuous wave and TR XEOL as a new analytical technique.
I also demonstrate the use of a technique used extensively within Biology has an
application with Earth sciences. The methodology incorporates the calculation of the natural lifetime of an emission through the relationship between the absorption and
emission coefficients. (Strickler and Berg, 1962). I discuss how knowledge of the natural
lifetime of an emission allows quantification of luminescence through measurement of a modified lifetime of emission. The quantification of a luminescent emission has significant potential within the geosciences one example being the identification of disputed emissions. I also consider the potential to use TR XEOL techniques in mapping
complex heterogeneous rocks and minerals
Author, Geraldine Brooks at the National Library of Australia for the 2009 Ray Mathew Lecture, Canberra, 23 October 2009 [picture] /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author, Geraldine Brooks during her visit to the National Library of Australia for the 2009 Ray Mathew Lecture, Canberra, 23 October 2009.; Acquired in digital format; access copy available online.; Mode of access: Internet via World Wide Web.; Photographed by a staff member of the National Library of Australia
Wedding party of Elizabeth Friend and Tim Whitney arriving the reception, Wirian, Bellevue Hill, New South Wales, 23 July 1934 [picture] /
No full textTitle devised from accompanying information where available.; Part of the: Fairfax archive of glass plate negatives.; Fairfax number: 5822.; Bridesmaids are Miss Jean Friend, Miss Denise Friend, Miss Laure Falkiner, Miss Diana Davidson, Miss Barbara Warry and Miss Thirza Whitney. Groomsmen are Mr Adrian Vickers, Mr Pat Hardy, Mr George Fuller, Mr Tony Mills, Mr R. Ashton and Mr J. Whitney.; Also available online at: http://nla.gov.au/nla.pic-vn6257002; Acquired from Fairfax Media, 2012
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Lodge Hill Camp, Caerleon, and the Hillforts of Gwent
No full textThis volume describes work on the Iron Age hillfort of Lodge Hill Camp, in Gwent, south-east Wales.Situated adjacent to the later Roman legionary fortress at Caerleon, the hillfort has, until recently, received little archaeological attention.Excavation was undertaken during the summer of 2000 within the interior of the hillfort, at its western entrance, and across the inner bank and ditch of the defences.An extended discussion is offered of Lodge Hills position within the regional Iron Age sequence, and of Roman and early Medieval reuse of hillforts in south Wales.The results of geophysical and earthwork survey at the hillfort of Llanmelin, near Chepstow, are also reported on
X-ray polarization in relativistic jets
No full textWe investigate the polarization properties of Comptonized X-rays from relativistic jets in active galactic nuclei (AGN) using Monte Carlo simulations. We consider three scenarios commonly proposed for the observed X-ray emission in AGN: Compton scattering of blackbody photons emitted from an accretion disc; scattering of cosmic microwave background (CMB) photons and self-Comptonization of intrinsically polarized synchrotron photons emitted by jet electrons. Our simulations show that for Comptonization of disc and CMB photons, the degree of polarization of the scattered photons increases with the viewing inclination angle with respect to the jet axis. In both cases, the maximum linear polarization is ≈20 per cent. In the case of synchrotron self-Comptonization (SSC), we find that the resulting X-ray polarization depends strongly on the seed synchrotron photon injection site, with typical fractional polarizations P≈ 10–20 per cent when synchrotron emission is localized near the jet base, while P≈ 20–70 per cent for the case of uniform emission throughout the jet. These results indicate that X-ray polarimetry may be capable of providing unique clues to identify the location of particle acceleration sites in relativistic jets. In particular, if synchrotron photons are emitted quasi-uniformly throughout a jet, then the observed degree of X-ray polarization may be sufficiently different for each of the competing X-ray emission mechanisms (synchrotron, SSC or external Comptonization) to determine which is the dominant process. However, X-ray polarimetry alone is unlikely to be able to distinguish between disc and CMB Comptonization
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Observations of the 57Fe+23 hyperfine transition in clusters of galaxies
No full textWe present a search for the hyperfine transition of the 57Fe+23 ion at 3.071 mm in clusters of galaxies with the ATNF Mopra telescope. The results are compared with a realistic estimate of the peak brightness temperature of the line in a cooling flow cluster A85, using the available X-ray data
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