158 research outputs found
Leveraging Mathematical Subject Information to Enhance Bibliometric Data
The field of mathematics is known to be especially challenging from a bibliometric point of view. Its bibliographic metrics are especially sensitive to distortions and are heavily influenced by the subject and its popularity. Therefore, quantitative methods are prone to misrepresentations, and need to take subject information into account. In this paper we investigate how the mathematical bibliography of the abstracting and reviewing service Zentralblatt MATH (zbMATH) could further benefit from the inclusion of mathematical subject information MSC2010. Furthermore, the mappings of MSC2010 to Linked Open Data resources have been upgraded and extended to also benefit from semantic information provided by DBpedia
Pigmentary and Other Dermatologic Manifestations of Minocycline: a reminder of adverse effects
The applications of the tetracycline class of antibiotics extends beyond their antimicrobial activity to anti-inflammatory, immunosuppressive and neuroprotective applications making it a commonly used class of medication. Minocycline, a second generation tetracycline, has inherent characteristics that improve absorption and distribution. These benefits promote even more wide spread use. This familiarity of usage breeds prescriptive complacency toward the dermatologic complications including hyperpigmentation. The following case explores these adverse manifestations of Minocycline use
Mechanical and microstructural features of plasma cut edges in a 15 mm thick S460M steel plate
In general, the thermal cutting processes of steel plates are considered to have an influence
on microstructures and residual stress distribution, which determines the mechanical properties
and performance of cut edges. They also affect the quality of the surface cut edges, which further
complicates the problem, because in most cases the surface is subjected to the largest stresses.
This paper studies the influence of plasma cutting processes on the mechanical behavior of the cut
edges of steel and presents the characterization results of straight plasma arc cut edges of steel plate
grade S460M, 15 mm thick. The cutting conditions used are the standard ones for industrial plasma
cutting. The metallography of CHAZ (Cut Heat Affected Zones) and hardness profiles versus distance
from plasma cut edge surface are tested; the mechanical behavior of different CHAZ layers under
the cut edge surface were obtained by testing of instrumented mini-tensile 300 µm thick specimens.
Also, the residual stress distribution in the CHAZ was measured by X-ray diffraction. The results for
the mechanical properties, microstructure, hardness, and residual stresses are finally compared and
discussed. This work concludes that the CHAZ resulting from the plasma cutting process is narrow
(about 700 µm) and homogeneous in plate thickness
Col-OSSOS: Colors of the Interstellar Planetesimal 1I/`Oumuamua
The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound
and hyperbolic orbit, offers a rare opportunity to explore the planetary
formation processes of other stars, and the effect of the interstellar
environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the
inner Solar System in 2017 October was a unique chance to make observations
matching those used to characterize the small-body populations of our own Solar
System. We present near-simultaneous g, r, and J photometry
and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North
Telescope, and photometry from the 4.2 m William Herschel Telescope. Our
grJ observations are directly comparable to those from the
high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS),
which offer unique diagnostic information for distinguishing between outer
Solar System surfaces. The J-band data also provide the highest signal-to-noise
measurements made of 1I/`Oumuamua in the near-infrared. Substantial, correlated
near-infrared and optical variability is present, with the same trend in both
near-infrared and optical. Our observations are consistent with 1I/`Oumuamua
rotating with a double-peaked period of hours and being a
highly elongated body with an axial ratio of at least 5.3:1, implying that it
has significant internal cohesion. The color of the first interstellar
planetesimal is at the neutral end of the range of Solar System and
solar-reflectance colors: it is like that of some dynamically excited objects
in the Kuiper belt and the less-red Jupiter Trojans.Comment: Accepted to ApJ
Adult Pulmonary Langerhans Cell Histiocytosis with Osseous Involvement: understanding this rare mimic of malignancy
Langerhans cells are dendritic cells that form the antigenic barrier of the human body. They occur in nearly any tissue but are most prevalent in the skin, submucosa of the bronchial tree, and other mucosae. Langerhans Cell Histiocytosis (LCH) develops when these cells damage the tissues in which they reside through a combination of inflammatory and monoclonal stimulation. The pulmonary variant of LCH involves the lung parenchyma and creates a wide variety of disturbances: pulmonary hypertension and both obstructive and restrictive lung disease. Osseous involvement, in addition to the pulmonary variant, presents with pulmonary masses and lytic bone lesions, which sparks suspicion for malignancy. Early recognition of this rare pathology is important as early treatment is clinically beneficial. The following explores a case of adult Pulmonary Langerhans Cell Histiocytosis with osseous involvement
Detection of fast radio transients with multiple stations: a case study using the Very Long Baseline Array
Recent investigations reveal an important new class of transient radio
phenomena that occur on sub-millisecond timescales. Often transient surveys'
data volumes are too large to archive exhaustively. Instead, an on-line
automatic system must excise impulsive interference and detect candidate events
in real-time. This work presents a case study using data from multiple
geographically distributed stations to perform simultaneous interference
excision and transient detection. We present several algorithms that
incorporate dedispersed data from multiple sites, and report experiments with a
commensal real-time transient detection system on the Very Long Baseline Array
(VLBA). We test the system using observations of pulsar B0329+54. The
multiple-station algorithms enhanced sensitivity for detection of individual
pulses. These strategies could improve detection performance for a future
generation of geographically distributed arrays such as the Australian Square
Kilometre Array Pathfinder and the Square Kilometre Array.Comment: 12 pages, 14 figures. Accepted for Ap
A pilot ASKAP survey for radio transients towards the Galactic Centre
We present the results of a radio transient and polarisation survey towards
the Galactic Centre, conducted as part of the Australian Square Kilometre Array
Pathfinder Variables and Slow Transients pilot survey. The survey region
consisted of five fields covering (, ). Each field was observed
for 12\,minutes, with between 7 and 9 repeats on cadences of between one day
and four months. We detected eight highly variable sources and seven highly
circularly-polarised sources (14 unique sources in total). Seven of these
sources are known pulsars including the rotating radio transient
PSR~J1739--2521 and the eclipsing pulsar PSR~J1723--2837. One of them is a low
mass X-ray binary, 4U 1758--25. Three of them are coincident with optical or
infrared sources and are likely to be stars. The remaining three may be related
to the class of Galactic Centre Radio Transients (including a highly likely
one, VAST~J173608.2--321634, that has been reported previously), although this
class is not yet understood. In the coming years, we expect to detect 40
bursts from this kind of source with the proposed four-year VAST survey if the
distribution of the source is isotropic over the Galactic fields.Comment: 17 pages, 13 figures, Accepted for publication in MNRA
A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages
Using a large sample of optical spectra of late-type dwarfs, we identify a
subset of late-M through L field dwarfs that, because of the presence of
low-gravity features in their spectra, are believed to be unusually young. From
a combined sample of 303 field L dwarfs, we find observationally that
7.6+/-1.6% are younger than 100 Myr. This percentage is in agreement with
theoretical predictions once observing biases are taken into account. We find
that these young L dwarfs tend to fall in the southern hemisphere (Dec < 0 deg)
and may be previously unrecognized, low-mass members of nearby, young
associations like Tucana-Horologium, TW Hydrae, beta Pictoris, and AB Doradus.
We use a homogeneously observed sample of roughly one hundred and fifty
6300-10000 Angstrom spectra of L and T dwarfs taken with the Low-Resolution
Imaging Spectrometer at the W. M. Keck Observatory to examine the strength of
the 6708-A Li I line as a function of spectral type and further corroborate the
trends noted by Kirkpatrick et al. (2000). We use our low-gravity spectra to
investigate the strength of the Li I line as a function of age. The data weakly
suggest that for early- to mid-L dwarfs the line strength reaches a maximum for
a few 100 Myr, whereas for much older (few Gyr) and much younger (<100 Myr) L
dwarfs the line is weaker or undetectable. We show that a weakening of lithium
at lower gravities is predicted by model atmosphere calculations, an effect
partially corroborated by existing observational data. Larger samples
containing L dwarfs of well determined ages are needed to further test this
empirically. If verified, this result would reinforce the caveat first cited in
Kirkpatrick et al. (2006) that the lithium test should be used with caution
when attempting to confirm the substellar nature of the youngest brown dwarfs.Comment: 73 pages with 22 figures; to appear in ApJ (Dec 20, 2008, v689n2
issue
A search for supernova-like optical counterparts to ASKAP-localised Fast Radio Bursts
Fast radio bursts (FRBs) are millisecond-scale radio pulses, which originate
in distant galaxies and are produced by unknown sources. The mystery remains
partially because of the typical difficulty in localising FRBs to host
galaxies. Accurate localisations delivered by the Commensal Real-time ASKAP
Fast Transients (CRAFT) survey now provide an opportunity to study the host
galaxies and potential transient counterparts of FRBs at a large range of
wavelengths. In this work, we investigate whether the first three FRBs
accurately localised by CRAFT have supernova-like transient counterparts. We
obtained two sets of imaging epochs with the Very Large Telescope for three
host galaxies, one soon after the burst detection and one several months later.
After subtracting these images no optical counterparts were identified in the
associated FRB host galaxies, so we instead place limits on the brightness of
any potential optical transients. A Monte Carlo approach, in which supernova
light curves were modelled and their base properties randomised, was used to
estimate the probability of a supernova associated with each FRB going
undetected. We conclude that Type Ia and IIn supernovae are unlikely to
accompany every apparently non-repeating FRB.Comment: 7 pages, 3 figures. Accepted to Astronomy & Astrophysics on 03 June
202
Disentangling the Cosmic Web Towards FRB 190608
FRB 190608 was detected by ASKAP and localized to a spiral galaxy at
in the SDSS footprint. The burst has a large dispersion
measure ( ) compared to the expected cosmic average at
its redshift. It also has a large rotation measure ( )
and scattering timescale ( at ). Chittidi et al
(2020) perform a detailed analysis of the ultraviolet and optical emission of
the host galaxy and estimate the host DM contribution to be
. This work complements theirs and reports the analysis of the optical
data of galaxies in the foreground of FRB 190608 to explore their contributions
to the FRB signal. Together, the two manuscripts delineate an observationally
driven, end-to-end study of matter distribution along an FRB sightline; the
first study of its kind. Combining KCWI observations and public SDSS data, we
estimate the expected cosmic dispersion measure along the
sightline to FRB 190608. We first estimate the contribution of hot, ionized gas
in intervening virialized halos ( ). Then,
using the Monte Carlo Physarum Machine (MCPM) methodology, we produce a 3D map
of ionized gas in cosmic web filaments and compute the DM contribution from
matter outside halos ( ). This implies a
greater fraction of ionized gas along this sightline is extant outside
virialized halos. We also investigate whether the intervening halos can account
for the large FRB rotation measure and pulse width and conclude that it is
implausible. Both the pulse broadening and the large Faraday rotation likely
arise from the progenitor environment or the host galaxy.Comment: 14 pages, 9 figures, 3 tables. The full version of Table 1 is
available as a LaTeX file. Only the first 10 entries are present in the print
version. Submitted to Ap
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