398 research outputs found
Speeds and arrival times of solar transients approximated by self-similar expanding circular fronts
The NASA STEREO mission opened up the possibility to forecast the arrival
times, speeds and directions of solar transients from outside the Sun-Earth
line. In particular, we are interested in predicting potentially geo-effective
Interplanetary Coronal Mass Ejections (ICMEs) from observations of density
structures at large observation angles from the Sun (with the STEREO
Heliospheric Imager instrument). We contribute to this endeavor by deriving
analytical formulas concerning a geometric correction for the ICME speed and
arrival time for the technique introduced by Davies et al. (2012, ApJ, in
press) called Self-Similar Expansion Fitting (SSEF). This model assumes that a
circle propagates outward, along a plane specified by a position angle (e.g.
the ecliptic), with constant angular half width (lambda). This is an extension
to earlier, more simple models: Fixed-Phi-Fitting (lambda = 0 degree) and
Harmonic Mean Fitting (lambda = 90 degree). This approach has the advantage
that it is possible to assess clearly, in contrast to previous models, if a
particular location in the heliosphere, such as a planet or spacecraft, might
be expected to be hit by the ICME front. Our correction formulas are especially
significant for glancing hits, where small differences in the direction greatly
influence the expected speeds (up to 100-200 km/s) and arrival times (up to two
days later than the apex). For very wide ICMEs (2 lambda > 120 degree), the
geometric correction becomes very similar to the one derived by M\"ostl et al.
(2011, ApJ, 741, id. 34) for the Harmonic Mean model. These analytic
expressions can also be used for empirical or analytical models to predict the
1 AU arrival time of an ICME by correcting for effects of hits by the flank
rather than the apex, if the width and direction of the ICME in a plane are
known and a circular geometry of the ICME front is assumed.Comment: 15 pages, 5 figures, accepted for publication in "Solar Physics
Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth
We investigate a CME propagating towards Earth on 29 March 2011. This event
is specifically chosen for its predominately northward directed magnetic field,
so that the influence from the momentum flux onto Earth can be isolated. We
focus our study on understanding how a small Earth-directed segment propagates.
Mass images are created from the white-light cameras onboard STEREO which are
also converted into mass height-time maps (mass J-maps). The mass tracks on
these J-maps correspond to the sheath region between the CME and its associated
shock front as detected by in situ measurements at L1. A time-series of mass
measurements from the STEREO COR-2A instrument are made along the Earth
propagation direction. Qualitatively, this mass time-series shows a remarkable
resemblance to the L1 in situ density series. The in situ measurements are used
as inputs into a 3D magnetospheric space weather simulation from CCMC. These
simulations display a sudden compression of the magnetosphere from the large
momentum flux at the leading edge of the CME and predictions are made for the
time-derivative of the magnetic field (dB/dt) on the ground. The predicted
dB/dt were then compared with observations from specific equatorially-located
ground stations and show notable similarity. This study of the momentum of a
CME from the Sun down to its influence on magnetic ground stations on Earth is
presented as preliminary proof of concept, such that future attempts may try to
use remote sensing to create density and velocity time-series as inputs to
magnetospheric simulations.Comment: Accepted for publication 8th March 2013. Submitted 18th Dec 2012. 19
Pages, 10 figures, 2 Appendice
LiftUpp: Support to Develop Learner Performance
Various motivations exist to move away from the simple assessment of
knowledge towards the more complex assessment and development of competence.
However, to accommodate such a change, high demands are put on the supporting
e-infrastructure in terms of intelligently collecting and analysing data. In
this paper, we discuss these challenges and how they are being addressed by
LiftUpp, a system that is now used in 70% of UK dental schools, and is finding
wider applications in physiotherapy, medicine and veterinary science. We
describe how data is collected for workplace-based development in dentistry
using a dedicated iPad app, which enables an integrated approach to linking and
assessing work flows, skills and learning outcomes. Furthermore, we detail how
the various forms of collected data can be fused, visualized and integrated
with conventional forms of assessment. This enables curriculum integration,
improved real-time student feedback, support for administration, and informed
instructional planning. Together these facets contribute to better support for
the development of learners' competence in situated learning setting, as well
as an improved experience. Finally, we discuss several directions for future
research on intelligent teaching systems that are afforded by using the design
present within LiftUpp.Comment: Short 4-page version to appear at AIED 201
The Automated Inspection of Opaque Liquid Vaccines
In the pharmaceutical industry the screening of opaque vaccines containing
suspensions is currently a manual task carried out by trained human visual
inspectors. We show that deep learning can be used to effectively automate this
process. A moving contrast is required to distinguish anomalies from other
particles, reflections and dust resting on a vial's surface. We train
3D-ConvNets to predict the likelihood of 20-frame video samples containing
anomalies. Our unaugmented dataset consists of hand-labelled samples, recorded
using vials provided by the HAL Allergy Group, a pharmaceutical company. We
trained ten randomly initialized 3D-ConvNets to provide a benchmark, observing
mean AUROC scores of 0.94 and 0.93 for positive samples (containing anomalies)
and negative (anomaly-free) samples, respectively. Using Frame-Completion
Generative Adversarial Networks we: (i) introduce an algorithm for computing
saliency maps, which we use to verify that the 3D-ConvNets are indeed
identifying anomalies; (ii) propose a novel self-training approach using the
saliency maps to determine if multiple networks agree on the location of
anomalies. Our self-training approach allows us to augment our data set by
labelling 217,888 additional samples. 3D-ConvNets trained with our augmented
dataset improve on the results we get when we train only on the unaugmented
dataset.Comment: 8 pages, 5 Figures, 3 Tables, ECAI 2020 Conference Proceeding
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Pre-existing invasive fungal infection is not a contraindication for allogeneic HSCT for patients with hematologic malignancies: a CIBMTR study.
Patients with prior invasive fungal infection (IFI) increasingly proceed to allogeneic hematopoietic cell transplantation (HSCT). However, little is known about the impact of prior IFI on survival. Patients with pre-transplant IFI (cases; n=825) were compared with controls (n=10247). A subset analysis assessed outcomes in leukemia patients pre- and post 2001. Cases were older with lower performance status (KPS), more advanced disease, higher likelihood of AML and having received cord blood, reduced intensity conditioning, mold-active fungal prophylaxis and more recently transplanted. Aspergillus spp. and Candida spp. were the most commonly identified pathogens. 68% of patients had primarily pulmonary involvement. Univariate and multivariable analysis demonstrated inferior PFS and overall survival (OS) for cases. At 2 years, cases had higher mortality and shorter PFS with significant increases in non-relapse mortality (NRM) but no difference in relapse. One year probability of post-HSCT IFI was 24% (cases) and 17% (control, P<0.001). The predominant cause of death was underlying malignancy; infectious death was higher in cases (13% vs 9%). In the subset analysis, patients transplanted before 2001 had increased NRM with inferior OS and PFS compared with later cases. Pre-transplant IFI is associated with lower PFS and OS after allogeneic HSCT but significant survivorship was observed. Consequently, pre-transplant IFI should not be a contraindication to allogeneic HSCT in otherwise suitable candidates. Documented pre-transplant IFI is associated with lower PFS and OS after allogeneic HSCT. However, mortality post transplant is more influenced by advanced disease status than previous IFI. Pre-transplant IFI does not appear to be a contraindication to allogeneic HSCT
The angiogenic factor midkine is regulated by dexamethasone and retinoic acid during alveolarization and in alveolar epithelial cells
<p>Abstract</p> <p>Background</p> <p>A precise balance exists between the actions of endogenous glucocorticoids (GC) and retinoids to promote normal lung development, in particular during alveolarization. The mechanisms controlling this balance are largely unknown, but recent evidence suggests that midkine (MK), a retinoic acid-regulated, pro-angiogenic growth factor, may function as a critical regulator. The purpose of this study was to examine regulation of MK by GC and RA during postnatal alveolar formation in rats.</p> <p>Methods</p> <p>Newborn rats were treated with dexamethasone (DEX) and/or all-trans-retinoic acid (RA) during the first two weeks of life. Lung morphology was assessed by light microscopy and radial alveolar counts. MK mRNA and protein expression in response to different treatment were determined by Northern and Western blots. In addition, MK protein expression in cultured human alveolar type 2-like cells treated with DEX and RA was also determined.</p> <p>Results</p> <p>Lung histology confirmed that DEX treatment inhibited and RA treatment stimulated alveolar formation, whereas concurrent administration of RA with DEX prevented the DEX effects. During normal development, MK expression was maximal during the period of alveolarization from postnatal day 5 (PN5) to PN15. DEX treatment of rat pups decreased, and RA treatment increased lung MK expression, whereas concurrent DEX+RA treatment prevented the DEX-induced decrease in MK expression. Using human alveolar type 2 (AT2)-like cells differentiated in culture, we confirmed that DEX and cAMP decreased, and RA increased MK expression.</p> <p>Conclusion</p> <p>We conclude that MK is expressed by AT2 cells, and is differentially regulated by corticosteroid and retinoid treatment in a manner consistent with hormonal effects on alveolarization during postnatal lung development.</p
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Overcoming Barriers to Vaccination By Empowering Citizens to Make Deliberate Choices
Copyright © The authors. Overcoming Barriers to Vaccination By Empowering Citizens to Make Deliberate Choices is one of ten in-depth transatlantic reports published by The British Academy exploring COVID-19 vaccine engagement in the UK and the US. For more details, see: https://www.thebritishacademy.ac.uk/news/the-british-academy-publishes-studies-examining-covid-vaccine-engagement-in-uk-and-usa/.British Academy (COVG7210005); Department for Business, Energy and Industrial Strategy.https://www.thebritishacademy.ac.uk/news/the-british-academy-publishes-studies-examining-covid-vaccine-engagement-in-uk-and-usa
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