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We present preliminary results from a programme designed to produce deep images of radio source fields drawn from the Parkes 2700 MHz and Molongolo 408 MHz catalogues using the charge-coupled-device (CCD) camera system built at the Institute of Astronomy, Cambridge. The programme is directed at a search both for faint extensions and nebulosity around radio QSOs and BL Lac objects and for faint objects in otherwise empty radio source fields; a detailed examination of the morphology of selected radio galaxies is also included.
A rapid and dramatic change in our views of the Universe which we have witnessed during the past two decades or so is often compared with what happened at the time of Galileo. Revolutionary role of the optical telescope then may be analogized with that of space-astronomy today which has drastically opened the new observational window to the Universe. The revolution is ongoing with a rapid pace or even being accelerated.
The 2011 investigations of the Caves Branch Archaeological Survey at the large and recently documented Maya site of Tipan Chen Uitz resulted in the discovery of the site's first monument with a glyphic inscription. Prior to this discovery, the site's glyphic corpus was limited to a small collection of texts rendered on fragmentary ceramics. In this paper, we describe these sherds as well as the monument (Monument 1), report on their archaeological contexts, provide an epigraphic analysis of the texts, and consider these written sources relative to our growing understanding of Tipan and its place in the ancient political landscape. The discovery of Monument 1 is important, for it stands to contribute to sociopolitical reconstructions in this part of the central Maya Lowlands and has significant implications for the possible presence of other, as yet undiscovered, Late Classic period (A.D. 550-830) monuments at Tipan.
Ion beam synthesis of CoSi2 layers in Si by MEVVA (Metal Vapor Vacuum Arc) implantation has been performed under various conditions. The formation and characteristics of these CoSi2 layers have been studied by XTEM, RBS, AFM, X-ray diffraction, ellipsometry, electrical and Hall effect measurements. It was found that a higher substrate temperature during implantation results in an as-implanted Co distribution closer to the surface and hence the formation of a shallower CoSi2 layer after annealing. Buried CoSi2 layers of good crystal quality and low resistivity CoSi2 can be formed by MEVVA implantation and annealing under appropriate conditions. A strong temperature dependence of the Hall coefficient showing a large peak at around 100K was observed for the CoSi2 layers formed in p-type Si substrates but not in n-type substrates. The properties and their dependence on the processing conditions, in particular, the substrate temperature during implantation, are presented and discussed.
This, the concluding paper of the Symposium, reviews the main issues in the Outer Hebrides concerning the interaction between the constituent parts of the environment and man's use of them, seeking to identify the existing impacts on the natural environment and speculating upon the character of possible future impacts. It aims to demonstrate how the findings of the environmental sciences, as exemplified by the information in the symposium papers, are relevant to the understanding and resolution of these issues and to identify important gaps in knowledge.
The relationship between land use planning and development control is discussed, particularly as it is reflected in the present system of Regional Reports, Structure Plans, Local Plans and the recently published National Planning Guidelines, and as it affects options for influencing future use of environmental resources in the Outer Hebrides.
Developments need management and, in some cases, monitoring. Both these activities require a contribution from the environmental sciences through an effective institutional framework.
The closing discussion examines some of the more general social issues, relating to the potential conflict between utilization of the environmental resource and conservation of the natural environment, which characterize isolated rural areas.
To identify those patients most at risk of developing a compressive post-operative haematoma following thyroid surgery.
Retrospective analysis of patients undergoing thyroid surgery. Factors associated with the group of patients who developed a post-operative haematoma were examined using a matched pairs, case–control design.
Following 355 thyroid operations, seven patients developed a post-operative haematoma requiring return to the operating theatre for bleeding control. A post-operative systolic blood pressure of greater than 150 mmHg, in the post-anaesthetic care unit, was the major significant factor identified by regression analysis (p = 0.002). Current smoking status was also a significant factor (p = 0.04).
In our facility, a post-anaesthetic systolic blood pressure in excess of 150 mmHg was associated with an increased risk of haemorrhage following thyroid surgery.
Two components of the electroluminescence (EL) from porous silicon light emitting diode (LED) devices have been observed. A slower component and a faster component have been identified. The slower component has a spectral peak shifted to the red from the corresponding photoluminescence (PL) spectrum. The faster component has a spectral peak well in the infrared (IR). Optical and electrical measurements of these two components are discussed. The temperature dependence of the two EL components are presented and contrasted. Our measurements demonstrate that the two EL components and the PL result from recombination in different parts of the porous silicon structure. As the temperature is reduced below room temperature the slower EL exhibits a decrease in intensity at relatively high temperatures, suggesting a freeze out of electrical carriers due to quantum confinement, resulting in a much reduced electrical excitation of the EL.
We have detected two dominant paramagnetic centers in porous silicon by electron paramagnetic resonance (EPR). One of them is isotropic, assigned to a defect in amorphous silicon oxide in the porous silicon layer. The other is anisotropic, and is very much like a Pb center at a planar Si/SiO2 interface. This EPR center is unambiguously identified as an •Si≡Si3 moiety, a silicon with dangling orbital, back-bonded to three silicon atoms, by 29 Si hyperfine structure (HFS) associated with the dangling orbital, and 29 Si superHFS from three neighboring silicon atoms, as similarly observed in the usual planar surface Pb structure. The dangling orbitals are highly localized and heavily p character. The disposition of dangling orbitals is evidence that the skeletal structure of luminescent porous silicon is crystalline and has a lattice which is aligned and continuous with the wafer substrate. The possibility that these centers are the major photoluminescent killers or quenchers is not supported by our hydrogen annealing experiments.
The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy , x-ray absorption spectroscopy [1,2,3,4], electron energy loss spectroscopy [2,3,4], Fano Effect measurements , and Bremstrahlung Isochromat Spectroscopy , including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples. [2,3,6]
The dynamic response of pixels from an a-Si:H imaging array are investigated and a model is developed to explain their observed behavior. Such arrays are under development for radiotherapy and diagnostic x-ray applications.
Light-sensitive hydrogenated amorphous silicon pixel arrays are now under development for real-time megavoltage and diagnostic fluoroscopic imaging. Such applications place stringent demands upon a variety of array properties including the uniformity of the light-response function of the pixels. It is desirable that the design and fabrication of these imaging arrays maximize such uniformity. The implications of uniformity for imaging are reviewed, and data obtained from small arrays are presented and discussed.
Shallow contact metallization of SiGeC was studied in anticipation of this alloys use in low power applications. It has been shown that in the solid state reaction of Co on (100) Si, that Co is the moving species with proper annealing conditions. This prevents the formation of Kirkendal voiding in certain device structures. This work studies the Co and Ti metallization of SiGeC. A bilayer of 44 nm of Co on 7 nm of Ti, were electron beam evaporated onto epitaxially grown Si0.77Ge0.21C0.02. The samples were rapid thermal processed at 600 and 900 °C for up to two minutes in a nitrogen ambient. The analysis techniques used were Rutherford backscattering spectrometry which included the used of the 4.27 MeV 12C(α,α) 12C resonance reaction, glancing angle x-ray diffraction, During annealing at all temperatures, Co diffused through the Ti layer and formed CoSi. This phase was confirmed by x-ray diffraction. The Co displaced the Ti to the surface. At 600 °C, Ge diffused to the surface layer, while at 900 °C it was rejected back into the original SiGeC. The sample annealed at 600 °C was subsequently annealed at 900 °C. The Ge in the surface layer was rejected from the surface layer, diffused across the CoSi and back into the SiGeC.
Ion beam synthesis of CoSi2 layers in Si by NIEVVA (Metal Vapor Vacuum Arc) implantation has been performed under various conditions. The formation and characteristics of these CoSi2 layers have been studied by XTEM, RBS, AFM, X-ray diffraction, ellipsometry, electrical and Hall effect measurements. It was found that a higher substrate temperature during implantation results in an as-implanted Co distribution closer to the surface and hence the formation of a shallower CoSi2 layer after annealing. Buried CoSi2 layers of good crystal quality and low resistivity CoSi2 can be formed by MEVVA implantation and annealing under appropriate conditions. A strong temperature dependence of the Hall coefficient showing a large peak at around 100K was observed for the CoSi2 layers formed in p-type Si substrates but not in n-type substrates. The properties and their dependence on the processing conditions, in particular, the substrate temperature during implantation, are presented and discussed.
Zn2SiO4:Mn thin films were deposited and studied as thin film phosphors for flat panel cathodoluminescent displays. Crystallized films with improved electrical conductivity were obtained after conventional and rapid thermal annealings in a N2 environment at 850Xy11100 °C for 0.25 to 60 minutes. A maximum cathodoluminescent efficiency of 1.3 Lm/W was achieved under dc excitation at 1500 volts. The luminescent emission from these thin films was peaked around 525 nm. The decay time of these films was controlled in the range of 2 to 10 ms by varying the deposition and annealing parameters. The fast response time of these thin films overcomes the long decay limitation of the Zn2SiO4:Mn powder phosphor in practical display applications.
The energy and the flux of impinging ions are important factors which determine the properties of deposited films and of exposed surfaces (microstructure, density, hardness, roughness, stress, chemical structure, adhesion etc.). In the present work, we use a multigrid retarding field analyzer to study ion bombardment characteristics in two different systems: a pulsed microwave plasma reactor, and a cold cathode ion source. We have found that the ion energy distribution functions (IEDF) possess specific features for each mode of operation: we evaluate the shape and the maximum and the mean ion energies of the IEDF for different gases such as Ar and N2. These ion characteristics are correlated with surface restructuring of differently treated polymers (polycarbonate and polyethylene terephthalate), analyzed by XPS.