133 research outputs found
Direct comparison of the performance of CZT detectors contacted with various metals
Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good
energy resolution over the broad energy range from several keV into the MeV
energy range. In this paper we present the results of a systematic study of the
performance of CZT detectors manufacturered by Orbotech (before IMARAD)
depending on surface preparation, contact materials and contact deposition. The
standard Orbotech detectors have the dimension of 2.0 x 2.0 x 0.5 cm. They have
a pixellated In anode with 8 x 8 pixels and a monolithic In cathode. Using the
same CZT substrates several times, we have made a direct comparison of the
performance of different contact materials by replacing the cathode and/or the
anode contacts with several high-workfunction metals. We present the
performance of the detectors and conclude with an overview over our ongoing
detector optimization.Comment: 8 pages, 5 figures, to appear in the proceedings of the conference
5922, "Hard X-Ray and Gamma-Ray Detector Physics VII" on the "Optics &
Photonics 2005" SPIE Symposium, July 31- August 4, 2005, San Diego, C
Thick CZT Detectors for Space-Borne X-ray Astronomy
Cadmium Zinc Telluride (CZT) detectors are having a major impact on the field
of hard X-ray astronomy. Without the need for cryogenic cooling they achieve
good spatial and energy resolutions over the broad energy range from 10 keV to
600 keV. In this paper, we briefly review the historical development of
detectors used in X-ray astronomy. Subsequently, we present an evaluation of
CZT detectors from the company Imarad. The standard 2x2x0.5 cm detectors,
contacted with 8x8 In pixels and an In cathode, exhibit FWHM energy resolutions
of 7 keV at 59 keV, and 10 keV at 662 keV. A direct measurement of the 662 keV
photopeak efficiency gives 67%. We have started a detailed study of the
performance of Imarad detectors depending on surface preparation, contact
materials, contact deposition, post-deposition detector annealing, and detector
passivation techniques. We present first results from contacting detectors with
Cr, Ag, Au, and Pt.Comment: Invited Contribution to the 49th International Symposium on Optical
Science and Technology (SPIE), August 2004, Denver, CO, SPIE, 49, 5540,
13.01. (2004
Detailed Studies of Pixelated CZT Detectors Grown with the Modified Horizontal Bridgman Method
The detector material Cadmium Zinc Telluride (CZT), known for its high
resolution over a broad energy range, is produced mainly by two methods: the
Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB)
process. This study is based on MHB CZT substrates from the company Orbotech
Medical Solutions Ltd. with a detector size of 2.0x2.0x0.5 cm^3, 8x8 pixels and
a pitch of 2.46 mm. Former studies have emphasized only on the cathode material
showing that high-work-function improve the energy resolution at lower
energies. Therfore, we studied the influence of the anode material while
keeping the cathode material constant. We used four different materials:
Indium, Titanium, Chromium and Gold with work-functions between 4.1 eV and 5.1
eV. The low work-function materials Indium and Titanium achieved the best
performance with energy resolutions: 2.0 keV (at 59 keV) and 1.9 keV (at 122
keV) for Titanium; 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium.
These detectors are very competitive compared with the more expensive ones
based on HPB material if one takes the large pixel pitch of 2.46 mm into
account. We present a detailed comparison of our detector response with 3-D
simulations, from which we determined the mobility-lifetime-products for
electrons and holes. Finally, we evaluated the temperature dependency of the
detector performance and mobility-lifetime-products, which is important for
many applications. With decreasing temperature down to -30C the breakdown
voltage increases and the electron mobility-lifetime-product decreases by about
30% over a range from 20C to -30C. This causes the energy resolution to
deteriorate, but the concomitantly increasing breakdown voltage makes it
possible to increase the applied bias voltage and restore the full performance.Comment: Accepted for publication in Astroparticle Physics, 25 pages, 13
figure
Структурная биология липоксигеназ: настоящее и перспективы развития
Lipoxygenases (LOX) form a heterogeneous family of lipid peroxidizing enzymes, which have been implicated in the synthesis of inflammatory mediators. The involvement of LOX isoenzymes in regulation of physiological homeostasis and pathogenesis of various diseases with major health and political relevance made them potential targets for pharmacological intervention. Although the first plant lipoxygenase (soybean LOX1) was discovered more than 60 years ago, the structural aspects of these enzymes were not studied until the mid 1990s. For the time being the crystal structures of various lipoxygenase-isoforms have been reported, and X-ray coordinates for numerous enzyme-ligand complexes are also available. This review focuses on recent developments in molecular enzymology of LOX and summarizes our current knowledge on the structural basis of LOX catalysis. Hypotheses explaining the reaction specificity of different isoforms as well as evolutionary aspects are reviewed and discussed. As the review is mainly intended to cover thematic priorities, which have not been reviewed in the past, a detailed discussion of the biological function of LOX goes beyond the scope of this review.Липоксигеназы (LOX) - ферменты перекисного окисления липидов - вовлечены в патогенез воспалительных и гиперпролиферативных реакций организма. Несмотря на то, что первая липоксигеназа растительного происхождения (LOX1 сои) была обнаружена более 60 лет назад, структурная биология этой группы ферментов не изучалась вплоть до середины 1990-ых годов. Данный обзор посвящен новейшим аспектам в области изучения молекулярной энзимологии липоксигеназ и обобщает существующие в настоящее время представления о структурных основах катализа с их участием. В обзоре рассмотрены различные гипотезы, объясняющие реакционную специфичность LOX, а также подведен промежуточный итог в области знания об эволюционном развитии этого класса ферментов в различных организмах. Несмотря на то, что биологическая роль LOX в низших организмах далеко не ясна, наличие в их ДНК последовательности LOX позволяет предположить, что семейство этих ферментов могло возникнуть сразу после появления атмосферного кислорода на Земле
CogStack - experiences of deploying integrated information retrieval and extraction services in a large National Health Service Foundation Trust hospital.
BACKGROUND: Traditional health information systems are generally devised to support clinical data collection at the point of care. However, as the significance of the modern information economy expands in scope and permeates the healthcare domain, there is an increasing urgency for healthcare organisations to offer information systems that address the expectations of clinicians, researchers and the business intelligence community alike. Amongst other emergent requirements, the principal unmet need might be defined as the 3R principle (right data, right place, right time) to address deficiencies in organisational data flow while retaining the strict information governance policies that apply within the UK National Health Service (NHS). Here, we describe our work on creating and deploying a low cost structured and unstructured information retrieval and extraction architecture within King's College Hospital, the management of governance concerns and the associated use cases and cost saving opportunities that such components present. RESULTS: To date, our CogStack architecture has processed over 300 million lines of clinical data, making it available for internal service improvement projects at King's College London. On generated data designed to simulate real world clinical text, our de-identification algorithm achieved up to 94% precision and up to 96% recall. CONCLUSION: We describe a toolkit which we feel is of huge value to the UK (and beyond) healthcare community. It is the only open source, easily deployable solution designed for the UK healthcare environment, in a landscape populated by expensive proprietary systems. Solutions such as these provide a crucial foundation for the genomic revolution in medicine
Electrical Sintering of Silver Nanoparticle Ink Studied by In-Situ TEM Probing
Metallic nanoparticle inks are used for printed electronics, but to reach acceptable conductivity the structures need to be sintered, usually using a furnace. Recently, sintering by direct resistive heating has been demonstrated. For a microscopic understanding of this Joule heating sintering method, we studied the entire process in real time inside a transmission electron microscope equipped with a movable electrical probe. We found an onset of Joule heating induced sintering and coalescence of nanoparticles at power levels of 0.1–10 mW/m3. In addition, a carbonization of the organic shells that stabilize the nanoparticles were found, with a conductivity of 4 105 Sm−1
Exploring the role of values and norms towards consumers’ intentions to patronize retail apparel brands engaged in corporate social responsibility (CSR)
The Monarch Initiative in 2019: an integrative data and analytic platform connecting phenotypes to genotypes across species.
In biology and biomedicine, relating phenotypic outcomes with genetic variation and environmental factors remains a challenge: patient phenotypes may not match known diseases, candidate variants may be in genes that haven’t been characterized, research organisms may not recapitulate human or veterinary diseases, environmental factors affecting disease outcomes are unknown or undocumented, and many resources must be queried to find potentially significant phenotypic associations. The Monarch Initiative (https://monarchinitiative.org) integrates information on genes, variants, genotypes, phenotypes and diseases in a variety of species, and allows powerful ontology-based search. We develop many widely adopted ontologies that together enable sophisticated computational analysis, mechanistic discovery and diagnostics of Mendelian diseases. Our algorithms and tools are widely used to identify animal models of human disease through phenotypic similarity, for differential diagnostics and to facilitate translational research. Launched in 2015, Monarch has grown with regards to data (new organisms, more sources, better modeling); new API and standards; ontologies (new Mondo unified disease ontology, improvements to ontologies such as HPO and uPheno); user interface (a redesigned website); and community development. Monarch data, algorithms and tools are being used and extended by resources such as GA4GH and NCATS Translator, among others, to aid mechanistic discovery and diagnostics
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