465,956 research outputs found
-dimensional Continued Fraction Algorithms Cheat Sheets
Multidimensional Continued Fraction Algorithms are generalizations of the
Euclid algorithm and find iteratively the gcd of two or more numbers. They are
defined as linear applications on some subcone of . We consider
multidimensional continued fraction algorithms that acts symmetrically on the
positive cone for . We include well-known and old ones
(Poincar\'e, Brun, Selmer, Fully Subtractive) and new ones
(Arnoux-Rauzy-Poincar\'e, Reverse, Cassaigne).
For each algorithm, one page (called cheat sheet) gathers a handful of
informations most of them generated with the open source software Sage with the
optional Sage package \texttt{slabbe-0.2.spkg}. The information includes the
-cylinders, density function of an absolutely continuous invariant measure,
domain of the natural extension, lyapunov exponents as well as data regarding
combinatorics on words, symbolic dynamics and digital geometry, that is,
associated substitutions, generated -adic systems, factor complexity,
discrepancy, dual substitutions and generation of digital planes.
The document ends with a table of comparison of Lyapunov exponents and gives
the code allowing to reproduce any of the results or figures appearing in these
cheat sheets.Comment: 9 pages, 66 figures, landscape orientatio
A Multi-wavelength Survey of AGN in Massive Clusters: AGN Detection and Cluster AGN Fraction
We aim to study the effect of environment on the presence and fuelling of
Active Galactic Nuclei (AGN) in massive galaxy clusters. We explore the use of
different AGN detection techniques with the goal of selecting AGN across a
broad range of luminosities, AGN/host galaxy flux ratios, and obscuration
levels. From a sample of 12 galaxy clusters at redshifts 0.5 < z < 0.9, we
identify AGN candidates using optical variability from multi-epoch HST imaging,
X-ray point sources in Chandra images, and mid-IR SED power-law fits through
the Spitzer IRAC channels. We find 178 optical variables, 74 X-ray point
sources, and 64 IR power law sources, resulting in an average of ~25 AGN per
cluster. We find no significant difference between the fraction of AGN among
galaxies in clusters and the percentage of similarly-detected AGN in field
galaxy studies (~2.5%). This result provides evidence that galaxies are still
able to fuel accretion onto their supermassive black holes, even in dense
environments. We also investigate correlations between the percentage of AGN
and cluster physical properties such as mass, X-ray luminosity, size,
morphology class and redshift. We find no significant correlations among
cluster properties and the percentage of AGN detected.Comment: 68 pages, 22 figures, 15 table
Binary Properties from Cepheid Radial Velocities (CRaV)
We have examined high accuracy radial velocities of Cepheids to determine the
binary frequency. The data are largely from the CORAVEL spectrophotometer and
the Moscow version, with a typical uncertainty of ~km~s, and a
time span from 1 to 20 years. A systemic velocity was obtained by removing the
pulsation component using a high order Fourier series. From this data we have
developed a list of stars showing no orbital velocity larger than
~km~s. The binary fraction was analyzed as a function of
magnitude, and yields an apparent decrease in this fraction for fainter stars.
We interpret this as incompleteness at fainter magnitudes, and derive the
preferred binary fraction of \% ( \% per decade of orbital
period) from the brightest 40 stars. Comparison of this fraction in this period
range (1-20 years) implies a large fraction for the full period range. This is
reasonable in that the high accuracy velocities are sensitive to the longer
periods and smaller orbital velocity amplitudes in the period range sampled
here. Thus the Cepheid velocity sample provides a sensitive detection in the
period range between short period spectroscopic binaries and resolved
companions. The recent identification of Cep as a binary with very low
amplitude and high eccentricity underscores the fact that the binary fractions
we derive are lower limits, to which other low amplitude systems will probably
be added. The mass ratio (q) distribution derived from ultraviolet observations
of the secondary is consistent with a flat distribution for the applicable
period range (1 to 20 years).Comment: accepted for publication in A
Transport, shot noise, and topology in AC-driven dimer arrays
We analyze an AC-driven dimer chain connected to a strongly biased electron
source and drain. It turns out that the resulting transport exhibits
fingerprints of topology. They are particularly visible in the driving-induced
current suppression and the Fano factor. Thus, shot noise measurements provide
a topological phase diagram as a function of the driving parameters. The
observed phenomena can be explained physically by a mapping to an effective
time-independent Hamiltonian and the emergence of edge states. Moreover, by
considering quantum dissipation, we determine the requirements for the
coherence properties in a possible experimental realization. For the
computation of the zero-frequency noise, we develop an efficient method based
on matrix-continued fractions.Comment: 8 pages, 6 figure
Interventions for the treatment of oral cavity and oropharyngeal cancer:chemotherapy
<b>Background:</b> Oral cavity and oropharyngeal cancers are frequently described as part of a group of oral cancers or head and neck cancer. Treatment of oral cavity cancer is generally surgery followed by radiotherapy, whereas oropharyngeal cancers, which are more likely to be advanced at the time of diagnosis, are managed with radiotherapy or chemoradiation. Surgery for oral cancers can be disfiguring and both surgery and radiotherapy have significant functional side effects, notably impaired ability to eat, drink and talk. The development of new chemotherapy agents, new combinations of agents and changes in the relative timing of surgery, radiotherapy, and chemotherapy treatments may potentially bring about increases in both survival and quality of life for this group of patients.<p></p>
<b>Objectives:</b> To determine whether chemotherapy, in addition to radiotherapy and/or surgery for oral cavity and oropharyngeal cancer results in improved survival, disease free survival, progression free survival, locoregional control and reduced recurrence of disease. To determine which regimen and time of administration (induction, concomitant or adjuvant) is associated with better outcomes.<p></p>
<b>Search strategy:</b> Electronic searches of the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE, EMBASE, AMED were undertaken on 28th July 2010. Reference lists of recent reviews and included studies were also searched to identify further trials.<p></p>
<b>Selection criteria:</b> Randomised controlled trials where more than 50% of participants had primary tumours in the oral cavity or oropharynx, and which compared the addition of chemotherapy to other treatments such as radiotherapy and/or surgery, or compared two or more chemotherapy regimens or modes of administration, were included.<p></p>
<b>Data collection and analysis:</b> Trials which met the inclusion criteria were assessed for risk of bias using six domains: sequence generation, allocation concealment, blinding, completeness of outcome data, selective reporting and other possible sources of bias. Data were extracted using a specially designed form and entered into the characteristics of included studies table and the analysis sections of the review. The proportion of participants in each trial with oral cavity and oropharyngeal cancers are recorded in Additional Table 1.<p></p>
<b>Main results:</b> There was no statistically significant improvement in overall survival associated with induction chemotherapy compared to locoregional treatment alone in 25 trials (hazard ratio (HR) of mortality 0.92, 95% confidence interval (CI) 0.84 to 1.00). Post-surgery adjuvant chemotherapy was associated with improved overall survival compared to surgery +/- radiotherapy alone in 10 trials (HR of mortality 0.88, 95% CI 0.79 to 0.99), and there was an additional benefit of adjuvant concomitant chemoradiotherapy compared to radiotherapy in 4 of these trials (HR of mortality 0.84, 95% CI 0.72 to 0.98). Concomitant chemoradiotherapy resulted in improved survival compared to radiotherapy alone in patients whose tumours were considered unresectable in 25 trials (HR of mortality 0.79, 95% CI 0.74 to 0.84). However, the additional toxicity attributable to chemotherapy in the combined regimens remains unquantified.<p></p>
<b>Authors' conclusions:</b> Chemotherapy, in addition to radiotherapy and surgery, is associated with improved overall survival in patients with oral cavity and oropharyngeal cancers. Induction chemotherapy is associated with a 9% increase in survival and adjuvant concomitant chemoradiotherapy is associated with a 16% increase in overall survival following surgery. In patients with unresectable tumours, concomitant chemoradiotherapy showed a 22% benefit in overall survival compared with radiotherapy alone.<p></p>
Star formation in Perseus: III. Outflows
We present a search for outflows towards 51 submillimetre cores in Perseus.
With consistently derived outflow properties from a large homogeneous dataset
within one molecular cloud we can investigate further the mass dependence and
time evolution of protostellar mass loss. Of the 51 cores, 37 show broad
linewings indicative of molecular outflows. In 13 cases, the linewings could be
due to confusion with neighbouring flows but 9 of those sources also have
near-infrared detections confirming their protostellar nature. The total
fraction of protostars in our sample is 65%. All but four outflow detections
are confirmed as protostellar by Spitzer IR detections and only one Spitzer
source has no outflow, showing that outflow maps at this sensitivity are
equally good at identifying protostars as Spitzer. Outflow momentum flux
correlates both with source luminosity and with core mass but there is
considerable scatter even within this one cloud despite the homogeneous
dataset. We fail to confirm the result of Bontemps et al. (1996) that Class I
sources show lower momentum fluxes on average than Class 0 sources, with a KS
test showing a significant probability that the momentum fluxes for both Class
0s and Class Is are drawn from the same distribution. We find that outflow
power may not show a simple decline between the Class 0 to Class I stages. Our
sample includes low momentum flux, low-luminosity Class 0 sources, possibly at
a very early evolutionary stage. If the only mass loss from the core were due
to outflows, cores would last for 10^5-10^8 years, longer than current
estimates of 1.5-4 x 10^5 years for the mean lifetime for the embedded phase.
Additional mechanisms for removing mass from protostellar cores may be
necessary.Comment: 26 pages, 21 figures. Version with full colour figures from
http://www.astro.ex.ac.uk/people/hatchell/RecentPapers/hatchell07_outflows.pd
Abell 2111: An Optical and Radio Study of the Richest Butcher-Oemler Cluster
We present an in-depth analysis of the Butcher-Oemler cluster A2111,
including new optical spectroscopy plus a deep Very Large Array (VLA) radio
continuum observation. These are combined with optical imaging from the Sloan
Digital Sky Survey (SDSS) to assess the activity and properties of member
galaxies. Prior X-ray studies have suggested A2111 is a head-on cluster merger,
a dynamical state which might be connected to the high level of activity
inferred from its blue fraction. We are able to directly assess this claim,
using our spectroscopic data to identify 95 cluster members among 196 total
galaxy spectra. These galaxy velocities do not themselves provide significant
evidence for the merger interpretation, however they are consistent with it
provided the system is viewed near the time of core passage and at a viewing
angle >~30 degrees different from the merger axis. The SDSS data allow us to
confirm the high blue fraction for A2111, f_b = 0.15 +/- 0.03 based on
photometry alone and f_b = 0.23 +/- 0.03 using spectroscopic data to remove
background galaxies. We are able to detect 175 optical sources from the SDSS in
our VLA radio data, of which 35 have redshift information. We use the SDSS
photometry to determine photometric redshifts for the remaining 140
radio-optical sources. In total we identify up to 26 cluster radio galaxies, 14
of which have spectroscopic redshifts. The optical spectroscopy and radio data
reveal a substantial population of dusty starbursts within the cluster. The
high blue fraction and prevalence of star formation is consistent with the
hypothesis that dynamically-active clusters are associated with more active
member galaxies than relaxed clusters.Comment: To appear in AJ; 53 pages including 10 figures and several long
table
- …