20,207 research outputs found
Stellar Motions in the Polar Ring Galaxy NGC 4650A
We present the first measurement of the stellar kinematics in the polar ring
of NGC 4650A. There is well defined rotation, with the stars and gas rotating
in the same direction, and with similar amplitude. The gaseous and stellar
kinematics suggest an approximately flat rotation curve, providing further
support for the hypothesis that the polar material resides in a disk rather
than in a ring. The kinematics of the emission line gas at and near the center
of the S0 suggests that the polar disk lacks a central hole. We have not
detected evidence for two, equal mass, counterrotating stellar polar streams,
as is predicted in the resonance levitation model proposed by Tremaine & Yu. A
merger seems the most likely explanation for the structure and kinematics of
NGC 4650A.Comment: 4 pages, accepted for publication in ApJ Letter
Shock-Wave Heating Model for Chondrule Formation: Prevention of Isotopic Fractionation
Chondrules are considered to have much information on dust particles and
processes in the solar nebula. It is naturally expected that protoplanetary
disks observed in present star forming regions have similar dust particles and
processes, so study of chondrule formation may provide us great information on
the formation of the planetary systems.
Evaporation during chondrule melting may have resulted in depletion of
volatile elements in chondrules. However, no evidence for a large degree of
heavy-isotope enrichment has been reported in chondrules. In order to meet this
observed constraint, the rapid heating rate at temperatures below the silicate
solidus is required to suppress the isotopic fractionation.
We have developed a new shock-wave heating model taking into account the
radiative transfer of the dust thermal continuum emission and the line emission
of gas molecules and calculated the thermal history of chondrules. We have
found that optically-thin shock waves for the thermal continuum emission from
dust particles can meet the rapid heating constraint, because the dust thermal
emission does not keep the dust particles high temperature for a long time in
the pre-shock region and dust particles are abruptly heated by the gas drag
heating in the post-shock region. We have also derived the upper limit of
optical depth of the pre-shock region using the radiative diffusion
approximation, above which the rapid heating constraint is not satisfied. It is
about 1 - 10.Comment: 58 pages, including 5 tables and 15 figures, accepted for publication
in The Astrophysical Journa
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The long-term outcome of treated high-risk nonmuscle-invasive bladder cancer
This article is available open access through the publisher’s website from the link below. Copyright © 2012 American Cancer Society.BACKGROUND: The treatment of high-risk nonmuscle-invasive bladder cancer (NMIBC) is difficult given its unpredictable natural history and patient comorbidities. Because current case series are mostly limited in size, the authors report the outcomes from a large, single-center series.
METHODS: The authors reviewed all patients with primary, high-risk NMIBC at their institution from 1994 to 2010. Outcomes were matched with clinicopathologic data. Patients who had muscle invasion within 6 months or had insufficient follow-up (<6 months) were excluded. Correlations were analyzed using multivariable Cox regression and log-rank analysis (2-sided; P < .05).
RESULTS: In total, 712 patients (median age, 73.7 years) were included. Progression to muscle invasion occurred in 110 patients (15.8%; 95% confidence interval [CI], 13%-18.3%) at a median of 17.2 months (interquartile range, 8.9-35.8 months), including 26.5% (95% CI, 22.2%-31.3%) of the 366 patients who had >5 years follow-up. Progression was associated with age (hazard ratio [HR], 1.04; P = .007), dysplastic urothelium (HR, 1.6; P = .003), urothelial cell carcinoma variants (HR, 3.2; P = .001), and recurrence (HR, 18.3; P .6).
CONCLUSIONS: Within a program of conservative treatment, progression of high-risk NMIBC was associated with a poor prognosis. Surveillance and bacillus Calmette-Guerin were ineffective in altering the natural history of this disease. The authors concluded that the time has come to rethink the paradigm of management of this disease.GlaxoSmithKline, Yorkshire Cancer Research, Sheffield Hospitals Charitable Trust, Astellas Educational Foundation, and the European Union
The Public Pays, the Corporation Profits: The Emasculation of the Public Purpose Doctrine and a Not-for-Profit Solution
Massive subsidies by state and local governments to private corporations for the purpose of inducing such corporations to retain or locate facilities in their respective locales are attracting greater public scrutiny. Commentators are beginning to question whether the public entity receives benefits anywhere near the value of the subsidy. In Virginia, where Governor George Allen proposed giving the Walt Disney Corporation $163 million in subsidies to establish a theme park, the public responded with bumper stickers that read Virginia Pays-Disney Profits
Gluon Fusion induced Zg and Zgg Productions in the Standard Model at the LHC
We report calculations of the gluon induced Zg and Zgg productions in the
Standard Model at the LHC operating at both 7 TeV and 14 TeV collision energy.
We present total cross sections and differential distributions of the processes
and compare them with the leading and next-to-leading order QCD pp -> Z+1 jet,
Z+2 jets results. Our results show that the gluon induced Zg and Zgg
productions contribute to pp -> Z+1 jet, Z+2 jets at 1% level.Comment: 8 pages, 5 figure
A really simple approximation of smallest grammar
In this paper we present a really simple linear-time algorithm constructing a
context-free grammar of size O(g log (N/g)) for the input string, where N is
the size of the input string and g the size of the optimal grammar generating
this string. The algorithm works for arbitrary size alphabets, but the running
time is linear assuming that the alphabet Sigma of the input string can be
identified with numbers from 1,ldots, N^c for some constant c. Algorithms with
such an approximation guarantee and running time are known, however all of them
were non-trivial and their analyses were involved. The here presented algorithm
computes the LZ77 factorisation and transforms it in phases to a grammar. In
each phase it maintains an LZ77-like factorisation of the word with at most l
factors as well as additional O(l) letters, where l was the size of the
original LZ77 factorisation. In one phase in a greedy way (by a left-to-right
sweep and a help of the factorisation) we choose a set of pairs of consecutive
letters to be replaced with new symbols, i.e. nonterminals of the constructed
grammar. We choose at least 2/3 of the letters in the word and there are O(l)
many different pairs among them. Hence there are O(log N) phases, each of them
introduces O(l) nonterminals to a grammar. A more precise analysis yields a
bound O(l log(N/l)). As l \leq g, this yields the desired bound O(g log(N/g)).Comment: Accepted for CPM 201
Scout motor performance analysis and prediction study /PAPS/
Scout motor performance analysis and predictio
The chemical connection between 67P/C-G and IRAS 16293-2422
The chemical evolution of a star- and planet-forming system begins in the
prestellar phase and proceeds across the subsequent evolutionary phases. The
chemical trail from cores to protoplanetary disks to planetary embryos can be
studied by comparing distant young protostars and comets in our Solar System.
One particularly chemically rich system that is thought to be analogous to our
own is the low-mass IRAS 16293-2422. ALMA-PILS observations have made the study
of chemistry on the disk scales (< 100 AU) of this system possible. Under the
assumption that comets are pristine tracers of the outer parts of the innate
protosolar disk, it is possible to compare the composition of our infant Solar
System to that of IRAS 16293-2422. The Rosetta mission has yielded a wealth of
unique in situ measurements on comet 67P/C-G, making it the best probe to date.
Herein, the initial comparisons in terms of the chemical composition and
isotopic ratios are summarized. Much work is still to be carried out in the
future as the analysis of both of these data sets is still ongoing.Comment: To appear in "Astrochemistry VII -- Through the Cosmos from Galaxies
to Planets", proceedings of the IAU Symposium No. 332, 2017, Puerto Varas,
Chile. M. Cunningham, T. Millar and Y. Aikawa, eds. (6 pages
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