290 research outputs found
Investigation of flame stretch in turbulent lifted jet flame
DNS data of a laboratory-scale turbulent lifted hydrogen jet flame has been analysed
to show that this flame has mixed mode combustion not only at the flame base but also
in downstream locations. The mixed mode combustion is observed in instantaneous
structures as in earlier studies and in averaged structure, in which the predominant
mode is found to be premixed combustion with varying equivalence ratio. The nonpremixed
combustion in the averaged structure is observed only in a narrow region
at the edge of the jet shear layer. The analyses of flame stretch show large probability
for negative flame stretch leading to negative surface averaged flame stretch. The
displacement speed-curvature correlation is observed to be negative contributing to
the negative flame stretch and partial premixing resulting from jet entrainment acts to
reduce the negative correlation. The contribution of turbulent straining to the flame
stretch is observed to be negative when the scalar gradient aligns with the most extensive
principal strain rate. The physics behind the negative flame stretch resulting from
turbulent straining is discussed and elucidated through a simple analysis of the flame
surface density transport equation.The authors are grateful for the inspiring discussion with Prof. K.N.C. Bray, and
financial support from Mitsubishi Heavy Industries (MHI) is gratefully acknowledged.
A part of this work is performed under the collaborative research between Cambridge
University and JAXA.This is an Accepted Manuscript of an article published by Taylor & Francis in Combustion Science and Technology on 24 February 2014, available online: http://wwww.tandfonline.com/10.1080/00102202.2013.877335
The MAGIC Telescope and the Observation of Gamma Ray Bursts
The MAGIC Telescope, now taking data with an energy threshold well below 100
GeV, will soon be able to take full advantage of the fast slewing capability of
its altazimuthal mount. Exploiting the link with the GCN network, the MAGIC
Telescope could be one of the first ground-based experiments able to see the
prompt emission of Gamma Ray Bursts in the few tens of GeV region.Comment: 4 pages, 1 figure (-> 3 subfigures), class file (cimento.cls)
included. To appear in: "Gamma-Ray Bursts in the Afterglow Era: 4rd
Workshop", Rome 200
GRB 050713A: High Energy Observations of the GRB Prompt and Afterglow Emission
Swift discovered GRB 050713A and slewed promptly to begin observing with its
narrow field instruments 72.6 seconds after the burst onset, while the prompt
gamma-ray emission was still detectable in the BAT. Simultaneous emission from
two flares is detected in the BAT and XRT. This burst marks just the second
time that the BAT and XRT have simultaneously detected emission from a burst
and the first time that both instruments have produced a well sampled,
simultaneous dataset covering multiple X-ray flares. The temporal rise and
decay parameters of the flares are consistent with the internal shock
mechanism. In addition to the Swift coverage of GRB 050713A, we report on the
Konus-Wind (K-W) detection of the prompt emission in the energy range 18-1150
keV, an upper limiting GeV measurement of the prompt emission made by the MAGIC
imaging atmospheric Cherenkov telescope and XMM-Newton observations of the
afterglow. Simultaneous observation between Swift XRT and XMM-Newton produce
consistent results, showing a break in the lightcurve at T+~15ks. Together,
these four observatories provide unusually broad spectral coverage of the
prompt emission and detailed X-ray follow-up of the afterglow for two weeks
after the burst trigger. Simultaneous spectral fits of K-W with BAT and BAT
with XRT data indicate that an absorbed broken powerlaw is often a better fit
to GRB flares than a simple absorbed powerlaw. These spectral results together
with the rapid temporal rise and decay of the flares suggest that flares are
produced in internal shocks due to late time central engine activity.Comment: 22 pages, 6 tables, 10 figures; Submitted to the Astrophysical
Journa
Virulence Potential of Staphylococcus aureus Strains Isolated From Diabetic Foot Ulcers: A new paradigm
OBJECTIVE—The purpose of this study was to assess the virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers and to discriminate noninfected from infected ulcers
Clinical and genetic characteristics of 10 Japanese patients with PROM1-associated retinal disorder: A report of the phenotype spectrum and a literature review in the Japanese population
Variants in the PROM1 gene are associated with cone (-rod) dystrophy, macular dystrophy, and other phenotypes. We describe the clinical and genetic characteristics of 10 patients from eight Japanese families with PROM1-associated retinal disorder (PROM1-RD) in a nationwide cohort. A literature review of PROM1-RD in the Japanese population was also performed. The median age at onset/examination of 10 patients was 31.0 (range, 10-45)/44.5 (22-73) years. All 10 patients showed atrophic macular changes. Seven patients (70.0%) had spared fovea to various degrees, approximately half of whom had maintained visual acuity. Generalized cone (-rod) dysfunction was demonstrated in all nine subjects with available electrophysiological data. Three PROM1 variants were identified in this study: one recurrent disease-causing variant (p.Arg373Cys), one novel putative disease-causing variant (p.Cys112Arg), and one novel variant of uncertain significance (VUS; p.Gly53Asp). Characteristic features of macular atrophy with generalized cone-dominated retinal dysfunction were shared among all 10 subjects with PROM1-RD, and the presence of foveal sparing was crucial in maintaining visual acuity. Together with the three previously reported variants [p.R373C, c.1551+1G>A (pathogenic), p.Asn580His (likely benign)] in the literature of Japanese patients, one prevalent missense variant (p.Arg373Cys, 6/9 families, 66.7%) detected in multiple studies was determined in the Japanese population, which was also frequently detected in the European population
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