96,604 research outputs found
Study of cosmogenic activation above ground for the DarkSide-20k experiment
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating γ role= presentation style= box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; \u3e�/β role= presentation style= box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; \u3e� background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods
The Filament Sensor for Near Real-Time Detection of Cytoskeletal Fiber Structures
A reliable extraction of filament data from microscopic images is of high
interest in the analysis of acto-myosin structures as early morphological
markers in mechanically guided differentiation of human mesenchymal stem cells
and the understanding of the underlying fiber arrangement processes. In this
paper, we propose the filament sensor (FS), a fast and robust processing
sequence which detects and records location, orientation, length and width for
each single filament of an image, and thus allows for the above described
analysis. The extraction of these features has previously not been possible
with existing methods. We evaluate the performance of the proposed FS in terms
of accuracy and speed in comparison to three existing methods with respect to
their limited output. Further, we provide a benchmark dataset of real cell
images along with filaments manually marked by a human expert as well as
simulated benchmark images. The FS clearly outperforms existing methods in
terms of computational runtime and filament extraction accuracy. The
implementation of the FS and the benchmark database are available as open
source.Comment: 32 pages, 21 figure
Use of colour for hand-filled form analysis and recognition
Colour information in form analysis is currently under utilised. As technology has advanced and computing costs have reduced, the processing of forms in colour has now become practicable. This paper describes a novel colour-based approach to the extraction of filled data from colour form images. Images are first quantised to reduce the colour complexity and data is extracted by examining the colour characteristics of the images. The improved performance of the proposed method has been verified by comparing the processing time, recognition rate, extraction precision and recall rate to that of an equivalent black and white system
The Arecibo Legacy Fast ALFA Survey: X. The HI Mass Function and Omega_HI From the 40% ALFALFA Survey
The Arecibo Legacy Fast ALFA (ALFALFA) survey has completed source extraction
for 40% of its total sky area, resulting in the largest sample of HI-selected
galaxies to date. We measure the HI mass function from a sample of 10,119
galaxies with 6.2 < log (M_HI/M_Sun) < 11.0 and with well-described mass errors
that accurately reflect our knowledge of low-mass systems. We characterize the
survey sensitivity and its dependence on profile velocity width, the effect of
large-scale structure, and the impact of radio frequency interference in order
to calculate the HIMF with both the 1/Vmax and 2DSWML methods. We also assess a
flux-limited sample to test the robustness of the methods applied to the full
sample. These measurements are in excellent agreement with one another; the
derived Schechter function parameters are phi* = 4.8 (+/- 0.3) * 10^-3, log
(M*/M_Sun) + 2 log(h_70) = 9.96 (+/- 0.2), and alpha = -1.33 (+/- 0.02). We
find Omega_HI = 4.3 (+/- 0.3) * 10^-4, 16% larger than the 2005 HIPASS result,
and our Schechter function fit extrapolated to log (M_HI/M_Sun) = 11.0 predicts
an order of magnitude more galaxies than HIPASS. The larger values of Omega_HI
and of M* imply an upward adjustment for estimates of the detection rate of
future large-scale HI line surveys with, e.g., the Square Kilometer Array. A
comparison with simulated galaxies from the Millennium Run and a treatment of
photoheating as a method of baryon removal from HI-selected halos indicates
that the disagreement between dark matter mass functions and baryonic mass
functions may soon be resolved.Comment: 21 pages, 13 figures, submitted to Ap
Deep rest-frame far-UV spectroscopy of the giant Lyman-alpha emitter 'Himiko'
We present deep 10h VLT/XSHOOTER spectroscopy for an extraordinarily luminous
and extended Lya emitter at z=6.595 referred to as Himiko and first discussed
by Ouchi et al. (2009), with the purpose of constraining the mechanisms
powering its strong emission. Complementary to the spectrum, we discuss NIR
imaging data from the CANDELS survey. We find neither for HeII nor any metal
line a significant excess, with 3 sigma upper limits of 6.8, 3.1, and
5.8x10^{-18} erg/s/cm^2 for CIV 1549, HeII 1640, CIII]
1909, respectively, assuming apertures with 200 km/s widths and offset
by -250 km/s w.r.t to the peak Lya redshift. These limits provide strong
evidence that an AGN is not a major contribution to Himiko's Lya flux. Strong
conclusions about the presence of PopIII star-formation or gravitational
cooling radiation are not possible based on the obtained HeII upper limit. Our
Lya spectrum confirms both spatial extent and flux (8.8+/-0.5x10^{-17}
erg/s/cm^2) of previous measurements. In addition, we can unambiguously exclude
any remaining chance of it being a lower redshift interloper by significantly
detecting a continuum redwards of Lya, while being undetected bluewards
The MUSE-Wide Survey: A first catalogue of 831 emission line galaxies
We present a first instalment of the MUSE-Wide survey, covering an area of
22.2 arcmin (corresponding to 20% of the final survey) in the
CANDELS/Deep area of the Chandra Deep Field South. We use the MUSE integral
field spectrograph at the ESO VLT to conduct a full-area spectroscopic mapping
at a depth of 1h exposure time per 1 arcmin pointing. We searched for
compact emission line objects using our newly developed LSDCat software based
on a 3-D matched filtering approach, followed by interactive classification and
redshift measurement of the sources. Our catalogue contains 831 distinct
emission line galaxies with redshifts ranging from 0.04 to 6. Roughly one third
(237) of the emission line sources are Lyman emitting galaxies with , only four of which had previously measured spectroscopic redshifts.
At lower redshifts 351 galaxies are detected primarily by their [OII] emission
line (), 189 by their [OIII] line (), and 46 by their H line (). Comparing our spectroscopic redshifts to photometric redshift estimates
from the literature, we find excellent agreement for with a median
of only and an outlier rate of 6%, however a
significant systematic offset of and an outlier rate of 23%
for Ly emitters at . Together with the catalogue we also release
1D PSF-weighted extracted spectra and small 3D datacubes centred on each of the
831 sources.Comment: 24 pages, 14 figures, accepted for publication in A&A, data products
are available for download from http://muse-vlt.eu/science/muse-wide-survey/
and later via the CD
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