643 research outputs found
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
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
First operation of an ACHINOS-equipped Spherical Proportional Counter with individual anode read-out
The multi-anode sensor ACHINOS revolutionised the spherical proportional
counter's capabilities by enabling large size, high pressure operation, and TPC
like capabilities through individual anode read-out. First measurements with an
individually read out ACHINOS are performed, which enables improved calibration
and response homogenisation. Experimental results demonstrating the improvement
in energy resolution brought by the individual anode calibration are presented.
These are complemented by detailed simulation studies on the effect of sensor
design and manufacturing imperfections, and how they may be corrected both in
hardware and analysis.Comment: 15 pages, 14 figure
Triplet exciton diffusion and phosphorescence quenching in Iridium(III)-Centered dendrimers
A study of triplet-triplet exciton annihilation and nonradiative decay in films of iridium(III)-centered phosphorescent dendrimers is reported. The average separation of the chromophore was tuned by the molecular structure and also by blending with a host material. It was found that triplet exciton hopping is controlled by electron exchange interactions and can be over 600 times faster than phosphorescence quenching. Nonradiative decay occurs by weak dipole-dipole interactions and is independent of exciton diffusion, except in very thin films
Experimental determination of proton hardness factors at several irradiation facilities
The effort to characterise detector sensors and components for the High Luminosity upgrade of the CERN Large Hadron Collider requires collaboration between irradiation facilities around the world. By convention, the radiation damage following irradiation with particle beams is reported as the 1 MeV neutron equivalent fluence, obtained using the corresponding hardness factor. Measurements of proton hardness factors at three different kinetic energies are presented, by characterisation of commercially available diodes before and after irradiation, using irradiations at the University of Birmingham, the Karlsruhe Institute of Technology, and CERN. Possible future improvements to these measurements are also discussed
Moving pictures of the human microbiome
BackgroundUnderstanding the normal temporal variation in the human microbiome is critical to developing treatments for putative microbiome-related afflictions such as obesity, Crohn’s disease, inflammatory bowel disease and malnutrition. Sequencing and computational technologies, however, have been a limiting factor in performing dense time series analysis of the human microbiome. Here, we present the largest human microbiota time series analysis to date, covering two individuals at four body sites over 396 timepoints.ResultsWe find that despite stable differences between body sites and individuals, there is pronounced variability in an individual’s microbiota across months, weeks and even days. Additionally, only a small fraction of the total taxa found within a single body site appear to be present across all time points, suggesting that no core temporal microbiome exists at high abundance (although some microbes may be present but drop below the detection threshold). Many more taxa appear to be persistent but non-permanent community members.ConclusionsDNA sequencing and computational advances described here provide the ability to go beyond infrequent snapshots of our human-associated microbial ecology to high-resolution assessments of temporal variations over protracted periods, within and between body habitats and individuals. This capacity will allow us to define normal variation and pathologic states, and assess responses to therapeutic interventions
Direct sequencing of the human microbiome readily reveals community differences
Future sequencing of the human microbiota will require greater breadth rather than depth
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
On the making and taking of professionalism in the further education workplace
This paper examines the changing nature of professional practice in English further education. At a time when neo-liberal reform has significantly impacted on this under-researched and over-market-tested sector, little is known about who its practitioners are and how they construct meaning in their work. Sociological interest in the field has tended to focus on further education practitioners as either the subjects of market and managerial reform or as creative agents operating within the contradictions of audit and inspection cultures. In challenging such dualism, which is reflective of wider sociological thinking, the paper examines the ways in which agency and structure combine to produce a more transformative conception of the further education professional. The approach contrasts with a prevailing policy discourse that seeks to re-professionalise and modernise further education practice without interrogating either the terms of its professionalism or the neo-liberal practices in which it resides
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