27,858 research outputs found
The Northern Anchovy reduction fishery for the 1978-79 through 1981-82 seasons
Nearly 49,000 metric tons (MT) of anchovies were taken during the 1978-79 season, followed by 32,390 MT in 1979-80, 60,678 MT in 1980-81 and 45,150 MT in 1981-82. A total of 14,076 fish was sampled during the four seasons for age,
length and sex. The fishery during the four seasons consisted mainly of young-of-the-year and age groups I and II fish. The 1978 and 1979 yr classes comprised the major
share of the catch. Seasonal mean lengths varied from 112 mm standard length (SL) in the 1979-80 season to 122 mm SL for the 1981-82 season. Female to male sex ratios ranged from 1.17:l (1978-79 season) to 1.59:l (1979-80 season). (28pp.
Fano-Kondo effect in a two-level system with triple quantum dots: shot noise characteristics
We theoretically compare transport properties of Fano-Kondo effect with those
of Fano effect. We focus on shot noise characteristics of a triple quantum dot
(QD) system in the Fano-Kondo region at zero temperature, and discuss the
effect of strong electric correlation in QDs. We found that the modulation of
the Fano dip is strongly affected by the on-site Coulomb interaction in QDs.Comment: 4 pages, 6figure
A pilot inference study for a beta-Bernoulli spatial scan statistic
The Bernoulli spatial scan statistic is used to detect localised clusters in binary labelled point data, such as that used in spatial or spatio-temporal case/control studies. We test the inferential capability of a recently developed beta-Bernoulli spatial scan statistic, which adds a beta prior to the original statistic. This pilot study, which includes two test scenarios with 6,000 data sets each,
suggests a marked increase in power for a given false alert rate. We suggest a more extensive study would be worthwhile to corroborate the findings. We also speculate on an explanation for the observed improvement
A Power-Enhanced Algorithm for Spatial Anomaly Detection in Binary Labelled Point Data Using the Spatial Scan Statistic [postprint]
This paper presents a novel modification to an existing algorithm for spatial anomaly detection in binary labeled point data sets, using the Bernoulli version of the Spatial Scan Statistic. We identify a potential ambiguity in p-values produced by Monte Carlo testing, which (by the selection of the most conservative p-value) can lead to sub-optimal power. When such ambiguity occurs, the modification uses a very inexpensive secondary test to suggest a less conservative p-value. Using benchmark tests, we show that this appears to restore power to the expected level, whilst having similarly retest variance to the original. The modification also appears to produce a small but significant improvement in overall detection performance when multiple anomalies are present
A spatial accuracy assessment of an alternative circular scan method for Kulldorff's spatial scan statistic
This paper concerns the Bernoulli version of Kulldorff’s spatial scan statistic, and how accurately it identifies the exact centre of approximately circular regions of increased spatial density in point data. We present an alternative method of selecting circular regions that appears to give greater accuracy. Performance is tested in an epidemiological context using manifold synthetic case-control datasets. A small, but statistically significant, improvement is reported. The power of the alternative method is yet to be assessed
The XMM-Newton slew survey in the 2-10 keV band
The XMM-Newton Slew Survey (XSS) covers a significant fraction of the sky in
a broad X-ray bandpass. Although shallow by contemporary standards, in the
`classical' 2-10 keV band of X-ray astronomy, the XSS provides significantly
better sensitivity than any currently available all-sky survey. We investigate
the source content of the XSS, focussing on detections in the 2-10 keV band
down to a very low threshold (> 4 counts net of background). At the faint end,
the survey reaches a flux sensitivity of roughly 3e-12 erg/cm2/s (2-10 keV).
Our starting point was a sample of 487 sources detected in the XMMSL1d2 XSS at
high galactic latitude in the hard band. Through cross-correlation with
published source catalogues from surveys spanning the electromagnetic spectrum
from radio to gamma-rays, we find that 45% of the sources have likely
identifications with normal/active galaxies, 18% are associated with other
classes of X-ray object (nearby coronally active stars, accreting binaries,
clusters of galaxies), leaving 37% of the XSS sources with no current
identification. We go on to define an XSS extragalactic hard band sample
comprised of 219 galaxies and active galaxies. We investigate the properties of
this extragalactic sample including its X-ray logN-logS distribution. We find
that in the low-count limit, the XSS is strongly affected by Eddington bias.
There is also a very strong bias in the XSS against the detection of extended
sources, most notably clusters of galaxies. A significant fraction of the
detections at and around the low-count limit may be spurious. Nevertheless, it
is possible to use the XSS to extract a reasonably robust sample of
extragalactic sources, excluding galaxy clusters. The differential logN-logS
relation of these extragalactic sources matches very well to the HEAO-1 A2
all-sky survey measurements at bright fluxes and to the 2XMM source counts at
the faint end.Comment: 16 pages, 13 figures, FITS table of XSS extragalactic sample
available from http://www.star.le.ac.uk/~amr30/Slew
- …
