1,485 research outputs found
Technique for producing highly planar Si/SiO0.64Ge0.36/Si metalâoxideâsemiconductor field effect transistor channels
Si/Si0.64Ge0.36/Si heterostructures have been grown at low temperature (450 °C) to avoid the strain-induced roughening observed for growth temperatures of 550 °C and above. The electrical properties of these structures are poor, and thought to be associated with grown-in point defects as indicated in positron annihilation spectroscopy. However, after an in situ annealing procedure (800 °C for 30 min) the electrical properties dramatically improve, giving an optimum 4 K mobility of 2500 cm2 V â 1 s â 1 for a sheet density of 6.2 Ă 1011 cm â 2. The low temperature growth yields highly planar interfaces, which are maintained after anneal as evidenced from transmission electron microscopy. This and secondary ion mass spectroscopy measurements demonstrate that the metastably strained alloy layer can endure the in situ anneal procedure necessary for enhanced electrical properties. Further studies have shown that the layers can also withstand a 120 min thermal oxidation at 800 °C, commensurate with metalâoxideâsemiconductor device fabrication
ACHINOS: A Multi-Anode Read-Out for Position Reconstruction and Tracking with Spherical Proportional Counters
The spherical proportional counter is a versatile gaseous detector with
physics applications ranging from rare event searches to fast neutron
spectroscopy. In its simplest form, the detector operates with a single channel
read-out, and uses pulse-shape information to reconstruct the interaction
radius, which is used for background discrimination and target volume
definition. Recent developments in the read-out instrumentation have enabled
the use of a multi-anode read-out structure, ACHINOS. The multiple anodes
provide information about the interaction position which, coupled with the
radial information, can be used to reconstruct an ionisation track. This
ability has implications for several applications of the detector, for example,
background discrimination in rare event searches.Comment: 4 pages, 3 figure
The evolution of vacancy-type defects in silicon-on-insulator structures studied by positron annihilation spectroscopy
Proton magnetic resonance spectra of plasma-deposited inorganic thin films
Proton magnetic resonance data are presented for the hydrogen alloys of plasma-deposited amorphous boron, carbon, silicon carbide, and silicon nitride. Linewidth and lineshape analysis leads to the conclusion that hydrogen nuclei are clustered in a-Si/C:H, a-C:H, and a-Si/C:H. Both a-Si/C:H and a-C:H data show that the hydrogen exists in two phases. Modeling of line- widths in a-Si/C:H indicates that the two phases are heavily hydrogenated carbon clusters imbedded in a weakly hydrogenated a-Si lattice. Finally, evidence is presented for the presence of motionally narrowed hydrogen spectra in a-Si/N:H, a-B:H, and a-C:H. It is suggested that the hydrogen nuclei giving rise to these spectra are associated with disorder modes
The golden circle: A way of arguing and acting about technology in the London ambulance service
This paper analyses the way in which the London Ambulance Service recovered from the events of October 1992, when it implemented a computer-aided despatch system (LASCAD) that remained in service for less than two weeks. It examines the enactment of a programme of long-term organizational change, focusing on the implementation of an alternative computer system in 1996. The analysis in this paper is informed by actor-network theory, both by an early statement of this approach developed by Callon in the sociology of translation, and also by concepts and ideas from Latourâs more recent restatement of his own position. The paper examines how alternative interests emerged and were stabilized over time, in a way of arguing and acting among key players in the change programme, christened the Golden Circle. The story traces four years in the history of the London Ambulance Service, from the aftermath of October 1992 through the birth of the Golden Circle to the achievement of National Health Service (NHS) trust status. LASCAD was the beginning of the story, this is the middle, an end lies in the future, when the remaining elements of the change programme are enacted beyond the Golden Circle
Polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) in urban soils of Greater London, UK
Surface soils from a 19 km2 area in east London, UK were analysed for polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) (n = 76). â16 PAH ranged from 4 to 67 mg/kg (mean, 18 mg/kg) and â50 PAH ranged from 6 to 88 mg/kg (mean, 25 mg/kg). â7 PCB ranged from 1 to 750 ÎŒg/kg (mean, 22 ÎŒg/kg) and âtri-hepta PCB ranged 9 to 2600 ÎŒg/kg (mean, 120 ÎŒg/kg). Compared to other international cities concentrations were similar for PAH but higher for PCB. Normal background concentrations (NBC) were calculated and compared to risk-based human health generic assessment criteria (GAC). Benzo[a]pyrene NBC for urban (6.9 mg/kg), semi-urban (4.4 mg/kg) and urban + semi urban (6 mg/kg) domains exceed residential (1 mg/kg) and allotment (2.2 mg/kg) LQM/CIEH GAC (at 6% SOM) and the Indeno[1,2,3-cd]pyrene NBC for urban (6.8 mg/kg) and urban + semi-urban (5.2 mg/kg) domains exceed the residential (4.2 mg/kg) LQM/CIEH GAC (at 6% SOM).
Capsule Abstract: Normal background concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls are elevated in east London soils and in some cases exceed regulatory assessment criteria
Fast Neutron Spectroscopy with a High-pressure Nitrogen-filled Large Volume Spherical Proportional Counter
We present a fast neutron spectroscopy system based on a nitrogen-filled,
large volume gaseous detector, the Spherical Proportional Counter. The system
has been successfully operated up to gas pressure of 1.5 bar. Neutron energy is
estimated through measurement of the 14N(n,a)11B and 14N(n,p)14C reaction
products. These reactions have comparable cross sections and Q-values with the
3He(n,p)3H reaction making nitrogen a good alternative to 3He use for fast
neutron detection. Two detectors were built at the University of Birmingham and
are currently used for the measurement of fast and thermal neutrons in the
University of Birmingham and the Boulby underground laboratory, respectively.Comment: 3 pages, 6 Figure
Host Species and Captivity Distinguish the Microbiome Compositions of a Diverse Zoo-Resident Non-Human Primate Population
Vast numbers of microorganisms inhabit the mammalian gastrointestinal tract in a complex community referred to as the gut microbiome. An individualâs microbiome may be impacted by genetics, diet, and various environmental factors, and has been associated with many health states and diseases, though specific explanations are lacking. While these communities are well-studied in human populations, non-human primates (NHPs), in particular zoo-resident or captive NHPs, offer distinct advantages to increasing our understanding of factors that influence gut microbiome composition. Here, we characterize the gut microbiome composition of a phylogenetically diverse cohort of NHPs residing in the same urban zoo. We show that despite overlapping and controlled environmental contexts, gut microbiomes are still distinguished between NHP host species. However, when comparing the zoo cohort to wild NHPs, we show that captivity status strongly distinguishes zoo-resident NHPs from their wild counterparts, regardless of host phylogeny. Microbial orders unique to captive NHPs include taxa commonly present in human gut microbiomes. Together, these results demonstrate that differences between NHP species are strongly associated with gut microbiome composition and diversity, suggesting that species-specific approaches should be considered when investigating environmental factorsâ influence on gut microbiome composition
The abolition of the General Teaching Council for England and the future of teacher discipline
With the abolition of the General Teaching Council for England in the 2011 Education Act, this article considers the future of teacher discipline in England. It provides a critique of the changes to the regulation of teacher misconduct and incompetence that draws on a Foucauldian framework, especially concerning the issue of public displays of discipline and the concomitant movement to more hidden forms. In addition, the external context of accountability that accompanies the reforms to teacher discipline are considered including the perfection of the panoptic metaphor presented by the changes to Ofsted practices such as the introduction of zero-notice inspections. The article concludes that the reforms will further move teachers from being occupational professionals to being organisational professionals marking them apart from comparable professions in medicine and law
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