4,226 research outputs found
Completeness of case ascertainment and survival time error in English cancer registries: impact on 1-year survival estimates.
BACKGROUND: It has been suggested that cancer registries in England are too dependent on processing of information from death certificates, and consequently that cancer survival statistics reported for England are systematically biased and too low. METHODS: We have linked routine cancer registration records for colorectal, lung, and breast cancer patients with information from the Hospital Episode Statistics (HES) database for the period 2001-2007. Based on record linkage with the HES database, records missing in the cancer register were identified, and dates of diagnosis were revised. The effects of those revisions on the estimated survival time and proportion of patients surviving for 1 year or more were studied. Cases that were absent in the cancer register and present in the HES data with a relevant diagnosis code and a relevant surgery code were used to estimate (a) the completeness of the cancer register. Differences in survival times calculated from the two data sources were used to estimate (b) the possible extent of error in the recorded survival time in the cancer register. Finally, we combined (a) and (b) to estimate (c) the resulting differences in 1-year cumulative survival estimates. RESULTS: Completeness of case ascertainment in English cancer registries is high, around 98-99%. Using HES data added 1.9%, 0.4% and 2.0% to the number of colorectal, lung, and breast cancer registrations, respectively. Around 5-6% of rapidly fatal cancer registrations had survival time extended by more than a month, and almost 3% of rapidly fatal breast cancer records were extended by more than a year. The resulting impact on estimates of 1-year survival was small, amounting to 1.0, 0.8, and 0.4 percentage points for colorectal, lung, and breast cancer, respectively. INTERPRETATION: English cancer registration data cannot be dismissed as unfit for the purpose of cancer survival analysis. However, investigators should retain a critical attitude to data quality and sources of error in international cancer survival studies
Anisotropic Distribution of SDSS Satellite Galaxies: Planar (not Polar) Alignment
The distribution of satellite galaxies relative to isolated host galaxies in
the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are
selected using three different methods, yielding samples of ~3300, ~1600, and
\~950 satellites. In the plane of the sky, the distributions of all three
samples show highly significant deviations from circular symmetry (> 99.99%, >
99.99%, and 99.79% confidence levels, respectively), and the degree of
anisotropy is a strong function of the projected radius, r_p, at which the
satellites are found. For r_p < 100 kpc, the SDSS satellites are aligned
preferentially with the major axes of the hosts. This is in stark contrast to
the Holmberg effect, in which satellites are aligned with the minor axes of
host galaxies. The degree of anisotropy in the distribution of the SDSS
satellites decreases with r_p and is consistent with an isotropic distribution
at of order the 1-sigma level for 250 kpc < r_p < 500 kpc.Comment: ApJ Letters (in press); Discussion section substantially revised,
SDSS DR3 included in the analysis, no significant changes to the result
Study of Foaming Properties and Effect of the Isomeric Distribution of Some Anionic Surfactants
Using different reaction conditions of photosulfochlorination of n-dodecane, two samples of anionic surfactants of sulfonate type are obtained. Their micellar behavior has been already reported and the relationship between their isomeric distribution and their chemical structures and micellar behaviors have been more thoroughly explored. In this investigation, we screened the foaming properties (foaming power and foam stability) by a standardized method very similar to the RossâMiles foaming tests to identify which surfactants are suitable for applications requiring high foaming, or, alternatively, low foaming. The results obtained for the synthesized surfactants are compared to those obtained for an industrial sample of secondary alkanesulfonate (Hostapur 60) and to those of a commercial sample of sodium dodecylsulfate used as reference for anionic surfactants. The foam formation and foam stability of aqueous solutions of the two samples of dodecanesulfonate are compared as a function of their isomeric distribution. These compounds show good foaming power characterized in most cases by metastable or dry foams. The highest foaming power is obtained for the sample rich in primary isomers which also produces foam with a relatively high stability. For the sample rich in secondary isomers we observe under fixed conditions a comparable initial foam height but the foam stability turns out to be low. This property is interesting for applications requiring low foaming properties such as dishwashing liquid for machines. The best results are observed near and above the critical micellar concentrations and at 25 C for both the samples
On the Relation Between Peak Luminosity and Parent Population of Type Ia Supernovae: A New Tool for Probing the Ages of Distant Galaxies
We study the properties of Type Ia Supernovae (SNe Ia) as functions of the
radial distance from their host galaxy centers. Using a sample of 62 SNe Ia
with reliable luminosity, reddening, and decline rate determinations, we find
no significant radial gradients of SNe Ia peak absolute magnitudes or decline
rates in elliptical+S0 galaxies, suggesting that the diversity of SN properties
is not related to the metallicity of their progenitors. We do find that the
range in brightness and light curve width of supernovae in spiral galaxies
extends to brighter, broader values. These results are interpreted as support
for an age, but not metallicity, related origin of the diversity in SNe Ia. If
confirmed with a larger and more accurate sample of data, the age-luminosity
relation would offer a new and powerful tool to probe the ages and age
gradients of stellar populations in galaxies at redshift as high as .
The absence of significant radial gradients in the peak and colors of SNe Ia supports the redding correction method of Phillips et
al (1999). We find no radial gradient in residuals from the SN Ia
luminosity-width relation, suggesting that the relation is not affected by
properties of the progenitor populations and supporting the reliability of
cosmological results based upon the use of SNe Ia as distance indicators.Comment: 19 pages, incl. 3 tables & 3 figures; to appear in Nov 2000 issue of
Ap
Spatial and kinematic alignments between central and satellite halos
Based on a cosmological N-body simulation we analyze spatial and kinematic
alignments of satellite halos within six times the virial radius of group size
host halos (Rvir). We measure three different types of spatial alignment: halo
alignment between the orientation of the group central substructure (GCS) and
the distribution of its satellites, radial alignment between the orientation of
a satellite and the direction towards its GCS, and direct alignment between the
orientation of the GCS and that of its satellites. In analogy we use the
directions of satellite velocities and probe three further types of alignment:
the radial velocity alignment between the satellite velocity and connecting
line between satellite and GCS, the halo velocity alignment between the
orientation of the GCS and satellite velocities and the auto velocity alignment
between the satellites orientations and their velocities. We find that
satellites are preferentially located along the major axis of the GCS within at
least 6 Rvir (the range probed here). Furthermore, satellites preferentially
point towards the GCS. The most pronounced signal is detected on small scales
but a detectable signal extends out to 6 Rvir. The direct alignment signal is
weaker, however a systematic trend is visible at distances < 2 Rvir. All
velocity alignments are highly significant on small scales. Our results suggest
that the halo alignment reflects the filamentary large scale structure which
extends far beyond the virial radii of the groups. In contrast, the main
contribution to the radial alignment arises from the adjustment of the
satellite orientations in the group tidal field. The projected data reveal good
agreement with recent results derived from large galaxy surveys. (abridged)Comment: accepted for publication in Ap
A method for the reconstruction of unknown non-monotonic growth functions in the chemostat
We propose an adaptive control law that allows one to identify unstable
steady states of the open-loop system in the single-species chemostat model
without the knowledge of the growth function. We then show how one can use this
control law to trace out (reconstruct) the whole graph of the growth function.
The process of tracing out the graph can be performed either continuously or
step-wise. We present and compare both approaches. Even in the case of two
species in competition, which is not directly accessible with our approach due
to lack of controllability, feedback control improves identifiability of the
non-dominant growth rate.Comment: expansion of ideas from proceedings paper (17 pages, 8 figures),
proceedings paper is version v
A generic map has no absolutely continuous invariant probability measure
Let be a smooth compact manifold (maybe with boundary, maybe
disconnected) of any dimension . We consider the set of maps
which have no absolutely continuous (with respect to Lebesgue)
invariant probability measure. We show that this is a residual (dense
C^1$ topology.
In the course of the proof, we need a generalization of the usual Rokhlin
tower lemma to non-invariant measures. That result may be of independent
interest.Comment: 12 page
Three Different Types of Galaxy Alignment within Dark Matter Halos
Using a large galaxy group catalogue based on the Sloan Digital Sky Survey
Data Release 4 we measure three different types of intrinsic galaxy alignment
within groups: halo alignment between the orientation of the brightest group
galaxies (BGG) and the distribution of its satellite galaxies, radial alignment
between the orientation of a satellite galaxy and the direction towards its
BGG, and direct alignment between the orientation of the BGG and that of its
satellites. In agreement with previous studies we find that satellite galaxies
are preferentially located along the major axis. In addition, on scales r < 0.7
Rvir we find that red satellites are preferentially aligned radially with the
direction to the BGG. The orientations of blue satellites, however, are
perfectly consistent with being isotropic. Finally, on scales r < 0.1 \Rvir, we
find a weak but significant indication for direct alignment between satellites
and BGGs. We briefly discuss the implications for weak lensing measurements.Comment: 4 pages, 4 figures, ApJL accepte
The Relationship Between Stellar Light Distributions of Galaxies and their Formation Histories
A major problem in extragalactic astronomy is the inability to distinguish in
a robust, physical, and model independent way how galaxy populations are
related to each other and to their formation histories. A similar, but
distinct, and also long standing question is whether the structural appearances
of galaxies, as seen through their stellar light distributions, contain enough
physical information to offer this classification. We argue through the use of
240 images of nearby galaxies that three model independent parameters measured
on a single galaxy image reveal its major ongoing and past formation modes, and
can be used as a robust classification system. These parameters quantitatively
measure: the concentration (C), asymmetry (A) and clumpiness (S) of a galaxy's
stellar light distribution. When combined into a three dimensional `CAS' volume
all major classes of galaxies in various phases of evolution are cleanly
distinguished. We argue that these three parameters correlate with important
modes of galaxy evolution: star formation and major merging activity. This is
argued through the strong correlation of Halpha equivalent width and broad band
colors with the clumpiness parameter, the uniquely large asymmetries of 66
galaxies undergoing mergers, and the correlation of bulge to total light
ratios, and stellar masses, with the concentration index. As an obvious goal is
to use this system at high redshifts to trace evolution, we demonstrate that
these parameters can be measured, within a reasonable and quantifiable
uncertainty, with available data out to z ~ 3 using the Hubble Space Telescope
GOODS ACS and Hubble Deep Field images.Comment: ApJS, in press, 30 pages, Figures 15 and 16 are in color. For a full
resolution version, please go to http://www.astro.caltech.edu/~cc/cas.p
Penicillium verrucosum occurrence and Ochratoxin A contents in organically cultivated grain with special reference to ancient wheat types and drying practice
This study addresses the relationship between the ochratoxigenic strains of Penicillium verrucosum and ochratoxin A (OTA) contents in organically cultivated grain. It included 37 combined, non-dried grain samples from farmers with no drying facilities as well as 19 non-dried and 22 dried samples from six farms with on-farm drying facilities (Case studies 1-6). The study focused on the ancient wheat type spelt but also included samples of wheat, rye, barley, oats, triticale, emmer, and einkorn. All 78 samples were analysed for moisture content (MC) and occurrence of P. verrucosum. The latter was assessed by plating non-disinfected kernels on DYSG agar and counting those contaminated by the fungus. Fiftyfive samples were analysed for OTA. Most of the combine harvested samples (82%) were contaminated with P. verrucosum prior to drying. This was ascribed to difficult harvest conditions and many samples of spelt, which was significantly more contaminated by P. verrucosum than oats, wheat and barley. Though not statistically significant, the results also indicated that spelt was more contaminated than rye, which is usually regarded the most sensitive small grain cereal. No correlation was found between number of kernels contaminated by P. verrucosum and OTA content. Despite many non-dried samples being contaminated by P. verrucosum, only two exceeded the EU maximum limit for grain (5 ng OTA g-1), both being spring spelt with 18 and 92 ng g-1, respectively. The problems were most likely correlated to a late harvest and high MC of the grain. The case studies showed exceedings of the maximum limit in a batch of dried oats and spring wheat, respectively, probably to be explained by insufficient drying of late harvested grain with high MC. Furthermore, our results clearly indicate that OTA is not produced in significant amounts in samples with MCs below 17%. All dried samples with MCs above 18% exceeded the 5 ng OTA g-1 limit in grain. However, no correlation between MC and the amount of OTA produced was found
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