15,113 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
Soft X‐ray and ENA Imaging of the Earth’s Dayside Magnetosphere
No full textThe LEXI and SMILE missions will provide soft X‐ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X‐ray and low‐ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X‐rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global‐scale magnetopause reconnection. When dayside imagers are installed with high‐ENA inner‐magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self‐standing manner without relying upon other observatories. Soft X‐ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather
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
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
Airway wall remodeling in asthma : novel mechanisms of human bronchial smooth muscle cells in the induction of angiogenesis
No full textAsthma is a global major health concern and it affects estimated 300 million people. The
prevalence of asthma is rising and there is no cure for asthma, only the symptoms can be
controlled. Acute asthma attacks are characterized by severe symptoms such as breathlessness,
wheezing, tightness of the chest, and coughing, which may lead to hospitalization or death.
Besides the acute symptoms, asthma is characterized by persistent airway inflammation and
airway wall remodeling. The term airway wall remodeling summarizes the structural changes in
the airway wall: epithelial cell shedding, goblet cell hyperplasia, hyperplasia and hypertrophy of
the bronchial smooth muscle (BSM) bundles, basement membrane thickening and increased
vascular density. Airway wall remodeling starts early in the pathogenesis of asthma and today it
is suggested that remodeling is a prerequisite for other asthma pathologies. Furthermore, novel
invasive therapies used to treat severe asthma provide evidence that the BSMC is a major
effector cell in the pathology of asthma.
In the present thesis novel mechanisms of BSMC regulation and their role in the induction of
asthma-associated angiogenesis have been elucidated. Therefore, the differences in the
angiogenic capacities of BSMC from asthma and non-asthma patients and their modification by
different conditions, such as an (i) inflammatory microenvironment, (ii) the influence of low
oxygen concentration, and (iii) the stimulation with the most potent asthma relevant allergen
(house dust mite (HDM) allergen) on the angiogenic properties of BSMC have been studied.
A major finding of this thesis is the increased angiogenic potential of BSMC from asthma
patients and the altered release of CXCR2 ligands in an in vitro inflammatory environment. It
has been demonstrated that BSMC from asthma patients release significantly more of the
CXCR2 ligands ENA-78, GRO-a and IL-8, which may explain the increased vascular density
in the sub-epithelial cell layers observed in the airways of asthma patients. These finding adds
to previous studies showing that BSMC are a source of angiogenic factors (e.g. VEGF) and that
CXCR2 ligands are elevated in the airway lining fluids of asthma patients. In this thesis BSMC
have been shown to be a potential source of CXCR2 ligands, which induced spout outgrowth
from endothelial cell spheroids in an in vitro model of angiogenesis.
Furthermore, this thesis investigated the effect of hypoxia on BSMC. Local restricted hypoxia
in the airways of asthma patients had only recently been suggested. The animal model based
hypothesis that hypoxia directly causes BSMC hyperplasia was tested. This hypothesis was not
confirmed in human BSMC but nonetheless it was demonstrated that hypoxia leads to
increased release of inflammatory and angiogenic mediators; as conditioned medium from
BSMC grown under hypoxia induced angiogenesis in an in vitro model via VEGF.
These findings suggest that different conditions or stimuli induce angiogenesis in asthma
through different pathways and therefore, different therapeutic strategies might be needed.
In the third part of this thesis the effect of HDM allergen on the release of inflammatory and
angiogenic mediators from BSMC was assessed. Animal models demonstrated that exposure to
HDM allergens increased airway wall vascularization. No direct contribution of BSMC to
HDM extract induced angiogenesis was observed. However, HDM extract proteases degraded
ENA-78, which is an import chemokine for neutrophil recruitment into the inflamed lung. Thus
HDM allergens may alter the bio-availability of ENA-78 in the airways of asthma patients and
modulate the immune response.
The findings of this thesis add a small piece to the knowledge of asthma pathology, the
mechanisms underlying airway wall remodeling and in particular BSMC hyperplasia and
neovascularization. This might represent novel targets for treatment, especially for the
prevention or reversal of airway wall remodeling
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
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
Hair casts due to a deodorant spray
No full textA 7-year-old girl presented with itching and greyish-white sleeve-like structures in her hair. After ruling out other possible causes for the symptoms, such as nits and dandruff, it was determined that the patient was affected by hair casts. These are small cylindrical structures resembling louse eggs that encircle individual scalp hairs and are easily movable along the hair shafts. It was concluded that she had induced the condition through misuse of a deodorant body spray. Scanning electron microscopy combined with electron dispersive X-ray analysis (X-ray microanalysis) of the hair casts showed the chemical nature of the structures. Some elements present in the composition of the ingredients of the deodorant spray, such as aluminium, chlorine, silicon, magnesium and carbon, were also present in this uncommon type of hair casts
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