284 research outputs found
Shock reflection and surface effects in the shock tube
A thin-film resistance thermometer, mounted on
the end-wall of a shock tube, is used to record
surface temperatures and heat transfer rates following
reflection of the primary shock wave.
This information is combined with the results of
theoretical investigations to produce simultaneous
information about surface accommodation effects and
gas thermal conductivities at high pressures and
moderate temperatures
Diagnostic accuracy of chest radiograph interpretation by graduate radiographers in Uganda
Background. Radiographers are increasingly being called on to take on new roles, such as X-ray film interpretation in imaging departments. In Uganda, where this study was conducted, there are just >40 radiologists in a population of ~40 million. In many hospitals, especially in rural areas, clinicians often rely on radiographers to obtain an opinion to assist with proper patient management. Therefore, Ugandan radiographers are being trained in basic radiographic interpretation to address the shortage of radiologists.
Objective. To determine the diagnostic accuracy of graduate radiographers in interpreting chest radiographs.
Methods. This was a cross-sectional retrospective study involving 57 graduate radiographers who were provided with 53 randomly selected chest radiographs to interpret. The validation of a radiographer’s interpretation of a radiograph was aided by the opinion of two senior radiologists. SPSS version 25 software (IBM Corp, USA) was used to analyse the findings and the radiographer’s performance was assessed using the receiver operating characteristic (ROC). The mean abnormality location sensitivity, overall radiographer sensitivity, specificity and false-positive rates were calculated.
Results. The radiographers’ diagnostic accuracy was high. The abnormality location sensitivity was 88.7%, overall sensitivity 76.6%, specificity 79.7% and false-positive rate 20.1%.
Conclusion. The study demonstrated that radiographers, if trained, can accurately report on chest radiographs to an acceptable standard
Visualising the structure of document search results: A comparison of graph theoretic approaches
This is the post-print of the article - Copyright @ 2010 Sage PublicationsPrevious work has shown that distance-similarity visualisation or ‘spatialisation’ can provide a potentially useful context in which to browse the results of a query search, enabling the user to adopt a simple local foraging or ‘cluster growing’ strategy to navigate through the retrieved document set. However, faithfully mapping feature-space models to visual space can be problematic owing to their inherent high dimensionality and non-linearity. Conventional linear approaches to dimension reduction tend to fail at this kind of task, sacrificing local structural in order to preserve a globally optimal mapping. In this paper the clustering performance of a recently proposed algorithm called isometric feature mapping (Isomap), which deals with non-linearity by transforming dissimilarities into geodesic distances, is compared to that of non-metric multidimensional scaling (MDS). Various graph pruning methods, for geodesic distance estimation, are also compared. Results show that Isomap is significantly better at preserving local structural detail than MDS, suggesting it is better suited to cluster growing and other semantic navigation tasks. Moreover, it is shown that applying a minimum-cost graph pruning criterion can provide a parameter-free alternative to the traditional K-neighbour method, resulting in spatial clustering that is equivalent to or better than that achieved using an optimal-K criterion
The effect of relationship status on communicating emotions through touch
Research into emotional communication to date has largely focused on facial and vocal expressions. In contrast, recent studies by Hertenstein, Keltner, App, Bulleit, and Jaskolka (2006) and Hertenstein, Holmes, McCullough, and Keltner (2009) exploring nonverbal communication of emotion discovered that people could identify anger, disgust, fear, gratitude, happiness, love, sadness and sympathy from the experience of being touched on either the arm or body by a stranger, without seeing the touch. The study showed that strangers were unable to communicate the self-focused emotions embarrassment, envy and pride, or the universal emotion surprise. Literature relating to touch indicates that the interpretation of a tactile experience is significantly influenced by the relationship between the touchers (Coan, Schaefer, & Davidson, 2006). The present study compared the ability of romantic couples and strangers to communicate emotions solely via touch. Results showed that both strangers and romantic couples were able to communicate universal and prosocial emotions, whereas only romantic couples were able to communicate the self-focused emotions envy and pride
Molecular dynamics simulation of the fragile glass former ortho-terphenyl: a flexible molecule model
We present a realistic model of the fragile glass former orthoterphenyl and
the results of extensive molecular dynamics simulations in which we
investigated its basic static and dynamic properties. In this model the
internal molecular interactions between the three rigid phenyl rings are
described by a set of force constants, including harmonic and anharmonic terms;
the interactions among different molecules are described by Lennard-Jones
site-site potentials. Self-diffusion properties are discussed in detail
together with the temperature and momentum dependencies of the
self-intermediate scattering function. The simulation data are compared with
existing experimental results and with the main predictions of the Mode
Coupling Theory.Comment: 20 pages and 28 postscript figure
Towards an effective potential for the monomer, dimer, hexamer, solid and liquid forms of hydrogen fluoride
We present an attempt to build up a new two-body effective potential for
hydrogen fluoride, fitted to theoretical and experimental data relevant not
only to the gas and liquid phases, but also to the crystal. The model is simple
enough to be used in Molecular Dynamics and Monte Carlo simulations. The
potential consists of: a) an intra-molecular contribution, allowing for
variations of the molecular length, plus b) an inter-molecular part, with three
charged sites on each monomer and a Buckingham "exp-6" interaction between
fluorines. The model is able to reproduce a significant number of observables
on the monomer, dimer, hexamer, solid and liquid forms of HF. The shortcomings
of the model are pointed out and possible improvements are finally discussed.Comment: LaTeX, 24 pages, 2 figures. For related papers see also
http://www.chim.unifi.it:8080/~valle
Calculation of The Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals
The band gap energy as well as the possibility of cross luminescence
processes in alkaline-earth dihalide crystals have been calculated using the ab
initio Perturbed-Ion (PI) model. The gap is calculated in several ways: as a
difference between one-electron energy eigenvalues and as a difference between
total energies of appropriate electronic states of the crystal, both at the HF
level and with inclusion of Coulomb correlation effects. In order to study the
possibility of ocurrence of cross luminescence in these materials, the energy
difference between the valence band and the upmost core band for some
representative crystals has been calculated. Both calculated band gap energies
and cross luminescence predictions compare very well with the available
experimental results.Comment: LaTeX file containing 8 pages plus 1 postscript figure. Final version
accepted for publication in The Journal of the Physical Society of Japan. It
contains a more complete list of references, as well as a more detailed
comparison with previous theoretical investigations on the subjec
Silent cerebral infarct after cardiac catheterization as detected by diffusion weighted Magnetic Resonance Imaging: a randomized comparison of radial and femoral arterial approaches
Background and objective: Cerebral microembolism detected by transcranial Doppler (TCD) occurs systematically
during cardiac catheterization, but its clinical relevance, remains unknown. Studies suggest that asymptomatic embolic
cerebral infarction detectable by diffusion-weighted (DW) MRI might exist after percutaneous cardiac interventions with
a frequency as high as 15 to 22% of cases. We have set up, for the first time, a prospective multicenter trial to assess the
rate of silent cerebral infarction after cardiac catheterization and to compare the impact of the arterial access site,
comparing radial and femoral access, on this phenomenon.
Study design: This prospective study will be performed in patients with severe aortic valve stenosis. To assess the
occurrence of cerebral infarction, all patients will undergo cerebral DW-MRI and neurological assessment within 24
hours before, and 48 hours after cardiac catheterization and retrograde catheterization of the aortic valve.
Randomization for the access site will be performed before coronary angiography. A subgroup will be monitored by
transcranial power M-mode Doppler during cardiac catheterization to observe cerebral blood flow and track emboli.
Neuropsychological tests will also be recorded in a subgroup of patients before and after the interventional procedures
to assess the impact of silent brain injury on potential cognitive decline. The primary end-point of the study is a direct
comparison of ischemic cerebral lesions as detected by serial cerebral DW-MRI between patients explored by radial
access and patients explored by femoral access. Secondary end-points include comparison of neuropsychological test
performance and number of microembolism signals observed in the two groups.
Implications: Using serial DW-MRI, silent cerebral infarction rate will be defined and the potential influence of vascular
access site will be evaluated. Silent cerebral infarction might be a major concern during cardiac catheterization and its
potential relationship to cognitive decline needs to be assessed.
Study registration: The SCIPION study is registered through National Institutes of Health-sponsored clinical trials
registry and has been assigned the Identifier: NCT 00329979
Reconstructing Roma History from Genome-Wide Data
The Roma people, living throughout Europe and West Asia, are a diverse population linked by the Romani language and culture. Previous linguistic and genetic studies have suggested that the Roma migrated into Europe from South Asia about 1,000–1,500 years ago. Genetic inferences about Roma history have mostly focused on the Y chromosome and mitochondrial DNA. To explore what additional information can be learned from genome-wide data, we analyzed data from six Roma groups that we genotyped at hundreds of thousands of single nucleotide polymorphisms (SNPs). We estimate that the Roma harbor about 80% West Eurasian ancestry–derived from a combination of European and South Asian sources–and that the date of admixture of South Asian and European ancestry was about 850 years before present. We provide evidence for Eastern Europe being a major source of European ancestry, and North-west India being a major source of the South Asian ancestry in the Roma. By computing allele sharing as a measure of linkage disequilibrium, we estimate that the migration of Roma out of the Indian subcontinent was accompanied by a severe founder event, which appears to have been followed by a major demographic expansion after the arrival in Europe.Országos Tudományos Kutatási Alapprogramok (OTKA K 103983)Országos Tudományos Kutatási Alapprogramok (OTKA 73430)National Science Foundation (U.S.) (HOMINID grant 1032255)National Institutes of Health (U.S.) (grant GM100233
Seed Regeneration Potential of Canopy Gaps at Early Formation Stage in Temperate Secondary Forests, Northeast China
Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m2). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation
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