2,143 research outputs found
Graded Lie algebras of maximal class IV
We describe the isomorphism classes of certain infinite-dimensional graded
Lie algebras of maximal class, generated by an element of weight one and an
element of weight two, over fields of odd characteristic.Comment: 38 pages. See also http://www-math.science.unitn.it/~caranti/ and
http://users.ox.ac.uk/~vlee
Presentations for the groups of order for prime
We list those presentations for the groups of order for prime
which are distributed as part of the {\sc SmallGroups} library
Particle-in-cell simulations of rf breakdown
Breakdown voltages of a capacitively coupled radio frequency argon discharge
at 27 MHz are studied. We use a one-dimensional electrostatic PIC code to
investigate the effect of changing the secondary emission properties of the
electrodes on the breakdown voltage, particularly at low pd values. Simulation
results are compared with the available experimental results and a satisfactory
agreement is found.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
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Local lung hypoxia determines epithelial fate decisions during alveolar regeneration.
After influenza infection, lineage-negative epithelial progenitors (LNEPs) exhibit a binary response to reconstitute epithelial barriers: activating a Notch-dependent ÎNp63/cytokeratin 5 (Krt5) remodelling program or differentiating into alveolar type II cells (AEC2s). Here we show that local lung hypoxia, through hypoxia-inducible factor (HIF1α), drives Notch signalling and Krt5pos basal-like cell expansion. Single-cell transcriptional profiling of human AEC2s from fibrotic lungs revealed a hypoxic subpopulation with activated Notch, suppressed surfactant protein C (SPC), and transdifferentiation toward a Krt5pos basal-like state. Activated murine Krt5pos LNEPs and diseased human AEC2s upregulate strikingly similar core pathways underlying migration and squamous metaplasia. While robust, HIF1α-driven metaplasia is ultimately inferior to AEC2 reconstitution in restoring normal lung function. HIF1α deletion or enhanced Wnt/ÎČ-catenin activity in Sox2pos LNEPs blocks Notch and Krt5 activation, instead promoting rapid AEC2 differentiation and migration and improving the quality of alveolar repair
What factors determine the severity of hepatitis Aârelated acute liver failure?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87020/1/j.1365-2893.2010.01410.x.pd
The Similarity of Broad Iron Lines in X-ray Binaries and Active Galactic Nuclei
We have compared the 2001 XMM-Newton spectra of the stellar mass black hole
binary XTE J1650-500 and the active galaxy MGC-6-30-15, focusing on the broad,
excess emission features at ~4--7 keV displayed by both sources. Such features
are frequently observed in both low mass X-ray binaries and active galactic
nuclei. For the former case it is generally accepted that the excess arises due
to iron emission, but there is some controversy over whether their width is
partially enhanced by instrumental processes, and hence also over the intrinsic
broadening mechanism. Meanwhile, in the latter case, the origin of this feature
is still subject to debate; physically motivated reflection and absorption
interpretations are both able to reproduce the observed spectra. In this work
we make use of the contemporaneous BeppoSAX data to demonstrate that the
breadth of the excess observed in XTE J1650-500 is astrophysical rather than
instrumental, and proceed to highlight the similarity of the excesses present
in this source and MGC-6-30-15. Both optically thick accretion discs and
optically thin coronae, which in combination naturally give rise to
relativistically-broadened iron lines when the disc extends close to the black
hole, are commonly observed in both class of object. The simplest solution is
that the broad emission features present arise from a common process, which we
argue must be reflection from the inner regions of an accretion disc around a
rapidly rotating black hole; for XTE J1650-500 we find spin constraints of 0.84
< a* < 0.98 at the 90 per cent confidence level. Other interpretations proposed
for AGN add potentially unnecessary complexities to the theoretical framework
of accretion in strong gravity.Comment: Accepted for publication in MNRAS; 22 pages, 17 figure
On the Finiteness Problem for Automaton (Semi)groups
This paper addresses a decision problem highlighted by Grigorchuk,
Nekrashevich, and Sushchanskii, namely the finiteness problem for automaton
(semi)groups.
For semigroups, we give an effective sufficient but not necessary condition
for finiteness and, for groups, an effective necessary but not sufficient
condition. The efficiency of the new criteria is demonstrated by testing all
Mealy automata with small stateset and alphabet. Finally, for groups, we
provide a necessary and sufficient condition that does not directly lead to a
decision procedure
Search Engine Similarity Analysis: A Combined Content and Rankings Approach
How different are search engines? The search engine wars are a favorite topic
of on-line analysts, as two of the biggest companies in the world, Google and
Microsoft, battle for prevalence of the web search space. Differences in search
engine popularity can be explained by their effectiveness or other factors,
such as familiarity with the most popular first engine, peer imitation, or
force of habit. In this work we present a thorough analysis of the affinity of
the two major search engines, Google and Bing, along with DuckDuckGo, which
goes to great lengths to emphasize its privacy-friendly credentials. To do so,
we collected search results using a comprehensive set of 300 unique queries for
two time periods in 2016 and 2019, and developed a new similarity metric that
leverages both the content and the ranking of search responses. We evaluated
the characteristics of the metric against other metrics and approaches that
have been proposed in the literature, and used it to (1) investigate the
similarities of search engine results, (2) the evolution of their affinity over
time, (3) what aspects of the results influence similarity, and (4) how the
metric differs over different kinds of search services. We found that Google
stands apart, but Bing and DuckDuckGo are largely indistinguishable from each
other.Comment: Shorter version of this paper was accepted in the 21st International
Conference on Web Information Systems Engineering (WISE 2020). The final
authenticated version is available online at
https://doi.org/10.1007/978-3-030-62008-0_
The On-Orbit Performance of the Galaxy Evolution Explorer
We report the first year on-orbit performance results for the Galaxy
Evolution Explorer (GALEX), a NASA Small Explorer that is performing a survey
of the sky in two ultraviolet bands. The instrument comprises a 50 cm diameter
modified Ritchey-Chretien telescope with a 1.25 degree field of view,
selectable imaging and objective grism spectroscopic modes, and an innovative
optical system with a thin-film multilayer dichroic beam splitter that enables
simultaneous imaging by a pair of photon counting, microchannel plate, delay
line readout detectors. Initial measurements demonstrate that GALEX is
performing well, meeting its requirements for resolution, efficiency,
astrometry, bandpass definition and survey sensitivity.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issu
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Coordinated airborne studies in the tropics (CAST)
This is the final version of the article. It first appeared from the American Meteorological Society via http://dx.doi.org/10.1175/BAMS-D-14-00290.1Abstract
The main field activities of the Coordinated Airborne Studies in the Tropics (CAST) campaign took place in the west Pacific during JanuaryâFebruary 2014. The field campaign was based in Guam (13.5°N, 144.8°E), using the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 atmospheric research aircraft, and was coordinated with the Airborne Tropical Tropopause Experiment (ATTREX) project with an unmanned Global Hawk and the Convective Transport of Active Species in the Tropics (CONTRAST) campaign with a Gulfstream V aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km. These measurements are providing new information about the processes influencing halogen and ozone levels in the tropical west Pacific, as well as the importance of trace-gas transport in convection for the upper troposphere and stratosphere. The FAAM aircraft made a total of 25 flights in the region between 1°S and 14°N and 130° and 155°E. It was used to sample at altitudes below 8 km, with much of the time spent in the marine boundary layer. It measured a range of chemical species and sampled extensively within the region of main inflow into the strong west Pacific convection. The CAST team also made ground-based measurements of a number of species (including daily ozonesondes) at the Atmospheric Radiation Measurement Program site on Manus Island, Papua New Guinea (2.1°S, 147.4°E). This article presents an overview of the CAST project, focusing on the design and operation of the west Pacific experiment. It additionally discusses some new developments in CAST, including flights of new instruments on board the Global Hawk in FebruaryâMarch 2015.CAST is funded by NERC and STFC, with grant NE/ I030054/1 (lead award), NE/J006262/1, NE/J006238/1, NE/J006181/1, NE/J006211/1, NE/J006061/1, NE/J006157/1, NE/J006203/1, NE/J00619X/1, and NE/J006173/1. N. R. P. Harris was supported by a NERC Advanced Research Fellowship (NE/G014655/1). P. I. Palmer acknowledges his Royal Society Wolfson Research Merit Award. The BAe-146-301 Atmospheric Research Aircraft is flown by Directflight Ltd and managed by the Facility for Airborne Atmospheric Measurements, which is a joint entity of the Natural Environment Research Council and the Met Office. The authors thank the staff at FAAM, Directflight and Avalon Aero who worked so hard toward the success of the aircraft deployment in Guam, especially for their untiring efforts when spending an unforeseen 9 days in Chuuk. We thank the local staff at Chuuk and Palau, as well as the authorities in the Federated States of Micronesia for their help in facilitating our research flights. Special thanks go to the personnel associated with the ARM facility at Manus, Papua New Guinea without whose help the ground-based measurements would not have been possible. Thanks to the British Atmospheric Data Centre (BADC) for hosting our data and the NCAS Atmospheric Measurement Facility for providing the radiosonde and ground-based ozone equipment. Chlorophyll-a data used in Figure 1 were extracted using the Giovanni online data system, maintained by the NASA GES DISC. We acknowledge the MODIS mission scientists and associated NASA personnel for the production of this data set. Finally we thank many individuals associated with the ATTREX and CONTRAST campaigns for their help in the logistical planning, and we would like to single out Jim Bresch for his excellent and freely provided meteorological advice
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