970 research outputs found
Gamma ray astronomy in the low energy range
No full textA low energy gamma ray telescope, and the results of its observations are described. The telescope consisted of four sodium iodide crystals, each of 120 cm2 area, occulted by lead discs. Charged particles are rejected using scintillation, anti-coincidence shields.The telescope was flown from Palestine, Texas in 1974. Gamma rays were observed from the Crab Nebula, the pulsar NP0 532, and the atmospheric background. No evidence for a gamma ray burst was found, giving an upper limit of less than 5.8 x 103 bursts per year of intensity greater than 1.6 x 10-6 ergs cm-2.Various types of existing, and planned, gamma ray detectors, and successful gamma ray observations are reviewed. Detailed calculations of the detection efficiency of a Double Compton telescope are presented and these results led to the development of the MISO low energy gamma ray telescope.Preliminary calculations of the detection efficiency of an Anticollimated Double Compton telescope are presented, which suggest that further, more detailed investigation of this type of detector would prove fruitful
Latest results on Jovian disk X-rays from XMM-Newton
No full textWe present the results of a spectral study of the soft X-ray emission (0.2–2.5 keV) from low-latitude (‘disk’) regions of Jupiter. The data were obtained during two observing campaigns with XMM-Newton in April and November 2003. While the level of the emission remained approximately the same between April and the first half of the November observation, the second part of the latter shows an enhancement by about 40% in the 0.2–2.5 keV flux. A very similar, and apparently correlated increase, in time and scale, was observed in the solar X-ray and EUV flux.
The months of October and November 2003 saw a period of particularly intense solar activity, which appears reflected in the behavior of the soft X-rays from Jupiter's disk. The X-ray spectra, from the XMM-Newton EPIC CCD cameras, are all well fitted by a coronal model with temperatures in the range 0.4–0.5 keV, with additional line emission from Mg XI (1.35 keV) and Si XIII (1.86 keV): these are characteristic lines of solar X-ray spectra at maximum activity and during flares.
The XMM-Newton observations lend further support to the theory that Jupiter's disk X-ray emission is controlled by the Sun, and may be produced in large part by scattering, elastic and fluorescent, of solar X-rays in the upper atmosphere of the planet
Multiscale Quantitative Imaging of Human Femoral Heads Using X-ray Microtomography
No full textPhDClinical diagnostic tools provide limited information on the underlying structural and mechanical properties of bone-tissue affected by degenerative and bone metabolic diseases. In-vivo bone failure studies provide limited information due to constraints such as X-ray dosage, cost and various other practicalities. In-vitro studies are thus required to enhance understanding of this phenomenon. The aims of this study were to use quantitative high-definition X-ray Micro-Tomography (XMT) to assess factors contributing to pathological and non-pathological bone failure and repair in relation to the mechanics of whole human femoral heads.
XMT images of one normal and six pathological femoral heads were collected at 26 – 8.8 μm voxel resolution and evaluated to determine structural features; bone mineral concentration (BMC); and using image analysis, identify microcallus formations. In addition, in-vitro compression tests were carried out on specimens taken from regions with different anatomical loading. Bone quality was then related to the anatomical loading and BMC.
Results from non-pathological tissue where used to establish a baseline for measurements of structural features. Microcallus formations where identified and used as markers to map the occurrence of bone damage. In osteoarthritic (OA) heads, the damage was found to be concentrated in localised clusters. Conversely, in the osteoporotic head damage was distributed homogeneously throughout the entire specimen. No significant difference in the BMC was observed, however there was a
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significant difference in the bone quality values between the non-pathological and pathological heads, and also between the pathologies. In-vitro mechanical testing revealed a difference in the mechanical properties of OA trabecular bone in relation to bone quality measurements but the samples exhibited no significant correlation to anatomical loading.
X-ray Ultra Microscopy (XuM) at 200nm and 775nm voxel resolution was used to investigate the nano-morphology of individual trabeculae. The XuM images showed differences in bone structure and fewer osteocyte lacunae present close to fracture site. XuM also identified micro-cracks within trabeculae that were encased by microcallus formations.
The application of novel quantitative high definition X-ray imaging to clinically relevant tissue at multiple length scales has provided new metrological data on the distribution of damage within pathological tissue. Insight into the vulnerability of diseased tissue to damage could ultimately lead to improved diagnosis from clinical radiographs
3-Dimensional simulation of multistage depressed collectors on microcomputers.
No full textA three-dimensional (3-D) package for simulation of asymmetric and crossed-field multistage depressed collectors for microwave tubes has been developed. This package is based upon the 3-D finite-difference code KOBRA3-INP. The main features of the package are a user-friendly input interface, postprocessors for collector analysis and calculation of secondary electron trajectories, and versatile output graphics. Both PC and. mainframe versions of the package have been developed. The results of simple benchmark tests and those of simulation and analysis of asymmetric and crossed-field collectors including the effects of secondary electrons are presented. It is found that the asymmetric hyperbolic electric field collector shows very low backstreaming. It is shown that the representation of trajectories in energy space gives a better insight into the behavior of individual trajectories than plotting in coordinate-space. The package will be useful for designing novel types of depressed collector
The role of iron in neurodegenerative disorders : insights and opportunities with synchrotron light
No full textThere is evidence for iron dysregulation in many forms of disease, including a broad spectrum of neurodegenerative disorders. In order to advance our understanding of the pathophysiological role of iron, it is helpful to be able to determine in detail the distribution of iron as it relates to metabolites, proteins, cells, and tissues, the chemical state and local environment of iron, and its relationship with other metal elements. Synchrotron light sources, providing primarily X-ray beams accompanied by access to longer wavelengths such as infra-red, are an outstanding tool for multi-modal non-destructive analysis of iron in these systems. The micro- and nano-focused X-ray beams that are generated at synchrotron facilities enable measurement of iron and other transition metal elements to be performed with outstanding analytic sensitivity and specificity. Recent developments have increased the scope for methods such as X-ray fluorescence mapping to be used quantitatively rather than semi-quantitatively. Burgeoning interest, coupled with technical advances and beamline development at synchrotron facilities, has led to substantial improvements in resources and methodologies in the field over the past decade. In this paper we will consider how the field has evolved with regard to the study of iron in proteins, cells, and brain tissue, and identify challenges in sample preparation and analysis. Selected examples will be used to illustrate the contribution, and future potential, of synchrotron X-ray analysis for the characterization of iron in model systems exhibiting iron dysregulation, and for human cases of neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease, Friedreich’s ataxia, and amyotrophic lateral sclerosis
Health Centres A Report and Discussion
No full textThis is a report (originally issued in February 1971) of the first phase of work, carried out at the Centre for Research in the Social Sciences of the University of Kent, into health centres and related aspects of primary medical care organisation. It presents the background in terms of
the state of knowledge about health centres for the later studies which were being developed by the group at the University of Kent and became part of the programme of the Health Services Research Unit. Since final reports on these studies are now being completed it seemed useful to
reissue the original (1971) report. The issues discussed remain relevant to policy decisions about health centres
Fort Worth Star-Telegram carrier salesmen and newsboys during group outing to Glen Rose
No full textFort Worth Star-Telegram carrier salesmen and newsboys posed on a rock feature while swimming during group outing to Glen Rose, Texas. Pictured on the rock are Robert Jennings, Amon G. Carter Jr., Ed Tate, John Terrell, W. C. Stafford, Raymond Ray, and Edwin Marcell. In the water are Jack Webb, Ad Richardson, and Willis Miller, lifeguards.https://mavmatrix.uta.edu/specialcollections_startelegram1930s/2439/thumbnail.jp
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Creating CZTS Thin Films Via Stacked Metallic CVD and Sulfurization
No full textCu2ZnSnS4 (CZTS) thin-film photovoltaics is an increasingly important area ofresearch for solar energy due to the high abundance and low toxicity of the elements used. A series of chemical vapor depositions (CVDs) with copper, tin, and zinc precursors were carried out to create layered thin films on quartz substrates. The viability of creating CZTS using these precursors was examined. As far as the author is aware, no work has yet been published on creating CZTS using the particular tin precursor that was used here, Dibutyltin Diacetate. Four different precursor stacking sequences were examined. Depositions were characterized using atomic force microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and four-point resistivity measurements. It was found that the ordering of precursors has a significant effect on the properties of the resulting thin films. The band gap energies were found to range from 1.08 eV to 2.02 eV
Geodesic Geometry of Black Holes
No full textThe study of geodesics is of intrinsic significance in the study of the geometry of space-time. In this thesis null, space-like and
time-like geodesics are studied in the case of the space-times of Schwarzschild, Reissner-Nordstrouml;m and Kerr black holes. These
space-times have been investigated with varying degrees of thoroughness in many articles and some books. However, there are some significant gaps in these treatments and the central aim of this thesis is to fill these gaps where necessary. Moreover, the following topics are covered for the first time.
1. In Chapter 4 a thorough treatment of the space-like geodesics of the Schwarzschild solutions has been given. These geodesics are the trajectories of Tachyons (faster than light particles) and are
treated in a complete manner. This has been done by obtaining exact solutions and solving them numerically.
2. In Part II all solutions for geodesics for a
Reissner-Nordstrouml;m black hole have been given in complete detail, i.e. time-like, null and space-like geodesics and orbit of a charged particle.
3. In Chapter 14 all solutions for geodesics in the equatorial plane of a Kerr black hole have been given in complete detail, i.e. time-like, null and space-like geodesics.
4. The study of special types of non-equatorial geodesics for a Kerr black hole have been given in complete detail, i.e. time-like (Chapter 17), null (Chapter 15) and space-like (Chapter 16). This has been done in order to distinguish the qualitatively different types of solutions.
Calculation of the explicit formulas, which describe these geodesics, as well as numerically computed diagrams representing the geodesics have been incorporated in these studies. The following subjects have been also treated:
5. Solutions for the geodesics in Reissner-Nordstrouml;m black holes with |Q_*| gt;= M, which are black holes with one (|Q_*| = M) or no horizon (|Q_*|gt; M) (Chapter 8).
6. Solutions of geodesics in extreme and fast Kerr black holes, i.e. black holes with a = M (extreme) and a gt; M (fast). As in the case of |Q_*| gt; M, fast black holes have naked singularities (Chapter 14).
7. Some general observations about orbit types of the Kerr black holes regarding relationships between parameters such as angular momentum, energy, Carter constant and mass and angular momentum of black holes (Chapter 13).
8. Some corrections to errors found in the literature.
While it has not been possible to cover all different cases which occur for possible relations amongst the parameters specifying a
general black hole, interesting geodesics have, however, been studied and a more thorough presentation of the properties of geodesics has now been given
For Outstanding Work
No full textHighlight of the annual meeting of the Birdville Classroom Teachers Association at Carter Field was the presentation of merit awards to top eight members. Shown here are seven of the award winners with M. E. Powell, left, re-elected president of the group. Winners are, left to right, Mrs. Clara Morgan, Mrs. Lora Roe, and Mrs. Thelma Ray. Standing, left to right, are John D. Miller, Mrs. Julia Kendall, Mrs. Mildred Long, and Mrs. Alliene Mullendore. Another winner, Mrs. Lillie Stokes, who could not be present is not shown in the picture. Published in Fort Worth Star-Telegram morning edition April 24, 1954.https://mavmatrix.uta.edu/specialcollections_startelegram1950s/32075/thumbnail.jp
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