11,677 research outputs found
Improving Pulsar Distances by Modelling Interstellar Scattering
We present here a method to study the distribution of electron density
fluctuations in pulsar directions as well as to estimate pulsar distances. The
method, based on a simple two-component model of the scattering medium
discussed by Gwinn et al. (1993), uses scintillation & proper motion data in
addition to the measurements of angular broadening & temporal broadening to
solve for the model parameters, namely, the fractional distance to a discrete
scatterer and the ascociated relative scattering strength. We show how this
method can be used to estimate pulsar distances reliably, when the location of
a discrete scatterer (e.g. an HII region), if any, is known. Considering the
specific example of PSR B0736-40, we illustrate how a simple characterization
of the Gum nebula region (using the data on the Vela pulsar) is possible and
can be used along with the temporal broadening measurements to estimate pulsar
distances.Comment: To be published in MNRAS, 7 pages, 3 figure
Upper Limits on the Pulsed Radio Emission from the Geminga Pulsar at 35 & 327 MHz
We report here our observations at 35 MHz and 327 MHz made in the direction
of the Gamma Ray pulsar Geminga. Based on the observed absence of any
significant pulsed emission from this source above our detection thresholds at
the two frequencies, we obtain useful upper-limits for the average flux to be
75-100 mJy at 35 MHz, and 0.2-0.3 mJy at 327 MHz. We discuss a few possible
reasons for the ``radio-quiet'' nature of this pulsar at frequencies other than
around 100 MHz.Comment: Accepted for publication in Astronomy & Astrophysic
The observational evidence pertinent to possible kick mechanisms in neutron stars
We examine available observations on pulsars for evidence pertaining to
mechanisms proposed to explain the origin of their velocities. We find that
mechanisms predicting a correlation between the rotation axis and the pulsar
velocity are ruled out. Also, that there is no significant correlation between
pulsar magnetic field strengths and velocities. With respect to recent
suggestions postulating asymmetric impulses at birth being solely responsible
for both the spins and velocities of pulsars, single impulses of any duration
and multiple extended duration impulses appear ruled out.Comment: 7 pages. Accepted for publication in Astronomy & Astrophysic
Healthcare Data Analytics on the Cloud
Meaningful analysis of voluminous health information has always been a challenge in most healthcare organizations. Accurate and timely information required by the management to lead a healthcare organization through the challenges found in the industry can be obtained using business intelligence (BI) or business analytics tools. However, these require large capital investments to implement and support the large volumes of data that needs to be analyzed to identify trends. They also require enormous processing power which places pressure on the business resources in addition to the dynamic changes in the digital technology. This paper evaluates the various nuances of business analytics of healthcare hosted on the cloud computing environment. The paper explores BI being offered as Software as a Service (SaaS) solution towards offering meaningful use of information for improving functions in healthcare enterprise. It also attempts to identify the challenges that healthcare enterprises face when making use of a BI SaaS solution
Search for Discrete Refractive Scattering Events
We have searched for discrete refractive scattering events (including effects
due to possible non-multiple diffractive scattering) at meter wavelengths in
the direction of two close by pulsars B0950+08 and B1929+10, where we looked
for spectral signatures associated with the multiple imaging of pulsars due to
scattering in the interstellar medium. We do not find any signatures of such
events in the direction of either source over a spectral periodicity range of
50 KHz to 5 MHz. Our analysis puts strong upper limits on the column density
contrast associated with a range of spatial scales of the interstellar electron
density irregularities along these lines of sight.Comment: Accepted for publication in Astronomy & Astrophysic
Evolution of Privacy Loss in Wikipedia
The cumulative effect of collective online participation has an important and
adverse impact on individual privacy. As an online system evolves over time,
new digital traces of individual behavior may uncover previously hidden
statistical links between an individual's past actions and her private traits.
To quantify this effect, we analyze the evolution of individual privacy loss by
studying the edit history of Wikipedia over 13 years, including more than
117,523 different users performing 188,805,088 edits. We trace each Wikipedia's
contributor using apparently harmless features, such as the number of edits
performed on predefined broad categories in a given time period (e.g.
Mathematics, Culture or Nature). We show that even at this unspecific level of
behavior description, it is possible to use off-the-shelf machine learning
algorithms to uncover usually undisclosed personal traits, such as gender,
religion or education. We provide empirical evidence that the prediction
accuracy for almost all private traits consistently improves over time.
Surprisingly, the prediction performance for users who stopped editing after a
given time still improves. The activities performed by new users seem to have
contributed more to this effect than additional activities from existing (but
still active) users. Insights from this work should help users, system
designers, and policy makers understand and make long-term design choices in
online content creation systems
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Case report: targeted whole exome sequencing enables the first prenatal diagnosis of the lethal skeletal dysplasia Osteocraniostenosis.
BACKGROUND: Osteocraniostenosis (OCS) is a rare genetic disorder characterised by premature closure of cranial sutures, gracile bones and perinatal lethality. Previously, diagnosis has only been possible postnatally on clinical and radiological features. This study describes the first prenatal diagnosis of OCS. CASE PRESENTATION: In this case prenatal ultrasound images were suggestive of a serious but non-lethal skeletal dysplasia. Due to the uncertain prognosis the parents were offered Whole Exome Sequencing (WES), which identified a specific gene mutation in the FAMIIIa gene. This mutation had previously been detected in two cases and was lethal in both perinatally. This established the diagnosis, a clear prognosis and allowed informed parental choice regarding ongoing pregnancy management. CONCLUSIONS: This case report supports the use of targeted WES prenatally to confirm the underlying cause and prognosis of sonographically suspected abnormalities
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