5,759 research outputs found
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The chronology of the 2002-2003 SARS mini pandemic.
Severe acute respiratory syndrome (SARS) was a new human disease in the autumn of 2002. It first occurred in Southern China in November 2002 and was transported to Hong Kong on February 21, 2003 by an infected and ill patient. Ten secondary cases spread the infection to two hospitals in Hong Kong and to Singapore, Toronto and Hanoi. In March 2003 a novel coronavirus (SARS-CoV) was found to be the causative agent. Within 11 weeks from the first SARS case in Hong Kong it had spread to an additional 27 countries or special administrative regions. The mini pandemic peaked during the last week of May 2003 and the last new probable case was on July 13, 2003. There were a total of 8096 probable cases and 774 deaths. Sixty-six per cent of the cases occurred in China, 22% in Hong Kong, 4% in Taiwan and 3% in both Singapore and Canada. Twenty-one per cent of all cases occurred in healthcare workers
Highly loaded multi-stage fan drive turbine: Performance of final three configurations
Results for a three-stage highly loaded fan drive turbine follow-on test program are presented. The effects of combinations of tandem and leaned bladerows on three-stage turbine performance were tested. The three-stage turbine with a tandem stator in stage two exhibited a total-to-total efficiency of approximately 0.887 as compared to 0.886 for the plain blade turbine base case
Energy efficient engine. Low pressure turbine test hardware detailed design report
The low pressure turbine for the energy efficient engine is a five-stage configuration with moderate aerodynamic loading incorporating advanced features of decambered airfoils and extended blade overlaps at platforms and shrouds. Mechanical integrity of 18,000 hours on flowpath components and 36,000 hours on all other components is achieved along with no aeromechanical instabilities within the steady-state operating range. Selection of a large number (156) of stage 4 blades, together with an increased stage 4 vane-to-blade gap, assists in achieving FAR 36 acoustic goals. Active clearance control (ACC) of gaps at blade tips and interstage seals is achieved by fan air cooling judiciously applied at responsive locations on the casing. This ACC system is a major improvement in preventing deterioration of the 0.0381 cm (0.015 in.) clearances required to meet the integrated-core/low-spool turbine efficiency goal of 91.1% and the light propulsion system efficiency goal of 91.7%
NASA/GE Energy Efficient Engine low pressure turbine scaled test vehicle performance report
The low pressure turbine for the NASA/General Electric Energy Efficient Engine is a highly loaded five-stage design featuring high outer wall slope, controlled vortex aerodynamics, low stage flow coefficient, and reduced clearances. An assessment of the performance of the LPT has been made based on a series of scaled air-turbine tests divided into two phases: Block 1 and Block 2. The transition duct and the first two stages of the turbine were evaluated during the Block 1 phase from March through August 1979. The full five-stage scale model, representing the final integrated core/low spool (ICLS) design and incorporating redesigns of stages 1 and 2 based on Block 1 data analysis, was tested as Block 2 in June through September 1981. Results from the scaled air-turbine tests, reviewed herein, indicate that the five-stage turbine designed for the ICLS application will attain an efficiency level of 91.5 percent at the Mach 0.8/10.67-km (35,000-ft), max-climb design point. This is relative to program goals of 91.1 percent for the ICLS and 91.7 percent for the flight propulsion system (FPS)
The role of M cells and the long QT syndrome in cardiac arrhythmias: simulation studies of reentrant excitations using a detailed electrophysiological model
In this numerical study, we investigate the role of intrinsic heterogeneities
of cardiac tissue due to M cells in the generation and maintenance of reentrant
excitations using the detailed Luo-Rudy dynamic model. This model has been
extended to include a description of the long QT 3 syndrome, and is studied in
both one dimension, corresponding to a cable traversing the ventricular wall,
and two dimensions, representing a transmural slice. We focus on two possible
mechanisms for the generation of reentrant events. We first investigate if
early-after-depolarizations occurring in M cells can initiate reentry. We find
that, even for large values of the long QT strength, the electrotonic coupling
between neighboring cells prevents early-after-depolarizations from creating a
reentry. We then study whether M cell domains, with their slow repolarization,
can function as wave blocks for premature stimuli. We find that the inclusion
of an M cell domain can result in some cases in reentrant excitations and we
determine the lifetime of the reentry as a function of the size and geometry of
the domain and of the strength of the long QT syndrome
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Subsecond total-body imaging using ultrasensitive positron emission tomography.
A 194-cm-long total-body positron emission tomography/computed tomography (PET/CT) scanner (uEXPLORER), has been constructed to offer a transformative platform for human radiotracer imaging in clinical research and healthcare. Its total-body coverage and exceptional sensitivity provide opportunities for innovative studies of physiology, biochemistry, and pharmacology. The objective of this study is to develop a method to perform ultrahigh (100 ms) temporal resolution dynamic PET imaging by combining advanced dynamic image reconstruction paradigms with the uEXPLORER scanner. We aim to capture the fast dynamics of initial radiotracer distribution, as well as cardiac motion, in the human body. The results show that we can visualize radiotracer transport in the body on timescales of 100 ms and obtain motion-frozen images with superior image quality compared to conventional methods. The proposed method has applications in studying fast tracer dynamics, such as blood flow and the dynamic response to neural modulation, as well as performing real-time motion tracking (e.g., cardiac and respiratory motion, and gross body motion) without any external monitoring device (e.g., electrocardiogram, breathing belt, or optical trackers)
A review of the design and assessment model of the Skills Challenge Certificate, and its place within the Welsh Baccalaureate
In January 2017, Wavehill, in collaboration with the University College London (UCL) Institute of Education (IOE), was commissioned by Qualifications Wales to undertake a review of the Skills Challenge Certificate (SCC) qualification and its place within the Welsh Baccalaureate (Welsh Bacc). Dr Caroline Daly (Reader in Education, IOE and Honorary Visiting Professor Cardiff University) undertook a detailed analysis of the SCC design by reviewing programme specifications, delivery handbooks, design principles, the administration handbook, the code of practice and Qualifications Wales’ (2016) Review of the implementation of the new Welsh Baccalaureate from September 2015. Dr Caroline Daly is the lead author on the desk-based review of the SCC. The review of documents was supplemented by interviews with key stakeholders, including the authors of the Qualifications Wales’ initial review (2016) of the Welsh Bacc and senior managers at the awarding body, WJEC. These interviews were used for reference to seek clarification about the SCC design and assessment model to inform the ongoing review of the documentation and refine questions for the focus groups. To enrich the evidence base, a programme of fieldwork was developed to sample a number of schools and Further Education (FE) colleges across Wales. The fieldwork engaged with learners and teachers through focus groups (learners) and interviews (teachers). The sample was constructed in discussion with Qualifications Wales and was designed to include the voices of learners and teachers from a variety of centres across Wales that deliver the Welsh Bacc (the methodology is discussed in section 3). The findings from the desk-based review, the learner focus groups and the teacher interviews are brought together in the Conclusions and Recommendations at the end of the report
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