1,745 research outputs found
Science Icebreaker Activities: An Example from Gravitational Wave Astronomy
At the beginning of a class or meeting an icebreaker activity is often used
to help loosen the group and get everyone talking. Our motivation is to develop
activities that serve the purpose of an icebreaker, but are designed to enhance
and supplement a science-oriented agenda. The subject of this article is an
icebreaker activity related to gravitational wave astronomy. We first describe
the unique gravitational wave signals from three distinct sources:
monochromatic binaries, merging compact objects, and extreme mass ratio
encounters. These signals form the basis of the activity where participants
work to match an ideal gravitational wave signal with noisy detector output for
each type of source.Comment: Accepted to The Physics Teacher. Original manuscript divided into two
papers at the request of the referee. For a related paper on gravitational
wave observatories see physics/050920
Hands-on Gravitational Wave Astronomy: Extracting astrophysical information from simulated signals
In this paper we introduce a hands-on activity in which introductory
astronomy students act as gravitational wave astronomers by extracting
information from simulated gravitational wave signals. The process mimics the
way true gravitational wave analysis will be handled by using plots of a pure
gravitational wave signal. The students directly measure the properties of the
simulated signal, and use these measurements to evaluate standard formulae for
astrophysical source parameters. An exercise based on the discussion in this
paper has been written and made publicly available online for use in
introductory laboratory courses.Comment: 5 pages, 4 figures; submitted to Am. J. Phy
A FABP4-PPARγ signaling axis regulates human monocyte responses to electrophilic fatty acid nitroalkenes
Nitro-fatty acids (NO2-FA) are electrophilic lipid mediators derived from unsaturated fatty acid nitration. These
species are produced endogenously by metabolic and inflammatory reactions and mediate anti-oxidative and
anti-inflammatory responses. NO2-FA have been postulated as partial agonists of the Peroxisome Proliferator-
Activated Receptor gamma (PPARγ), which is predominantly expressed in adipocytes and myeloid cells. Herein,
we explored molecular and cellular events associated with PPARγ activation by NO2-FA in monocytes and
macrophages. NO2-FA induced the expression of two PPARγ reporter genes, Fatty Acid Binding Protein 4
(FABP4) and the scavenger receptor CD36, at early stages of monocyte differentiation into macrophages. These
responses were inhibited by the specific PPARγ inhibitor GW9662. Attenuated NO2-FA effects on PPARγ sig-
naling were observed once cells were differentiated into macrophages, with a significant but lower FABP4 up-
regulation, and no induction of CD36. Using in vitro and in silico approaches, we demonstrated that NO2-FA bind
to FABP4. Furthermore, the inhibition of monocyte FA binding by FABP4 diminished NO2-FA-induced upre-
gulation of reporter genes that are transcriptionally regulated by PPARγ, Keap1/Nrf2 and HSF1, indicating that
FABP4 inhibition mitigates NO2-FA signaling actions. Overall, our results affirm that NO2-FA activate PPARγ in
monocytes and upregulate FABP4 expression, thus promoting a positive amplification loop for the downstream
signaling actions of this mediator
Extreme mass ratio inspiral rates: dependence on the massive black hole mass
We study the rate at which stars spiral into a massive black hole (MBH) due
to the emission of gravitational waves (GWs), as a function of the mass M of
the MBH. In the context of our model, it is shown analytically that the rate
approximately depends on the MBH mass as M^{-1/4}. Numerical simulations
confirm this result, and show that for all MBH masses, the event rate is
highest for stellar black holes, followed by white dwarfs, and lowest for
neutron stars. The Laser Interferometer Space Antenna (LISA) is expected to see
hundreds of these extreme mass ratio inspirals per year. Since the event rate
derived here formally diverges as M->0, the model presented here cannot hold
for MBHs of masses that are too low, and we discuss what the limitations of the
model are.Comment: Accepted to CQG, special LISA issu
Clinical features and management of children with primary ciliary dyskinesia in England
Objective In England, the National Health Service commissioned a National Management Service for children with primary ciliary dyskinesia (PCD). The aims of this study were to describe the health of children seen in this Service and compare lung function to children with cystic fibrosis (CF).
Design Multi-centre service evaluation of the English National Management PCD Service.
Setting Four nationally commissioned PCD centres in England.
Patients 333 children with PCD reviewed in the Service in 2015; lung function data were also compared to 2970 children with CF.
Results Median age at diagnosis for PCD was 2.6 years, significantly lower in children with situs inversus (1.0 vs 6.0 years, p<0.0001). Compared with national data from the CF Registry, mean (SD) %predicted FEV1 76.8% in PCD (n=240) and 85.0% in CF, and FEV1 was lower in children with PCD up to the age of 15 years. Approximately half of children had some hearing impairment, with 26% requiring hearing aids. Children with a lower BMI had lower FEV1 (p<0.001). One third of children had positive respiratory cultures at review, 54% of these grew Haemophilus influenzae.
Conclusions We provide evidence that children with PCD in England have worse lung function than those with CF. Nutritional status should be considered in PCD management, as those with a lower BMI have significantly lower FEV1. Hearing impairment is common but seems to improve with age. Well designed and powered randomised controlled trials on management of PCD are needed to inform best clinical practice
Gravitomagnetic corrections on gravitational waves
Gravitational waveforms and production could be considerably affected by
gravitomagnetic corrections considered in relativistic theory of orbits. Beside
the standard periastron effect of General Relativity, new nutation effects come
out when c^{-3} corrections are taken into account. Such corrections emerge as
soon as matter-current densities and vector gravitational potentials cannot be
discarded into dynamics. We study the gravitational waves emitted through the
capture, in the gravitational field of massive binary systems (e.g. a very
massive black hole on which a stellar object is inspiralling) via the
quadrupole approximation, considering precession and nutation effects. We
present a numerical study to obtain the gravitational wave luminosity, the
total energy output and the gravitational radiation amplitude. From a crude
estimate of the expected number of events towards peculiar targets (e.g.
globular clusters) and in particular, the rate of events per year for dense
stellar clusters at the Galactic Center (SgrA*), we conclude that this type of
capture could give signatures to be revealed by interferometric GW antennas, in
particular by the forthcoming laser interferometer space antenna LISA.Comment: 14 pages, 7 figure
Topological data analysis reveals genotype-phenotype relationships in primary ciliary dyskinesia
Background: Primary ciliary dyskinesia (PCD) is a heterogeneous inherited disorder caused by mutations in approximately 50 cilia-related genes. PCD genotype-phenotype relationships have mostly arisen from small case series because existing statistical approaches to investigate relationships have been unsuitable for rare diseases. /
Methods: We applied a topological data analysis (TDA) approach to investigate genotype-phenotype relationships in PCD. Data from separate training and validation cohorts included 396 genetically defined individuals carrying pathogenic variants in PCD genes. To develop the TDA models, twelve clinical and diagnostic variables were included. TDA-driven hypotheses were subsequently tested using traditional statistics. /
Results: Disease severity at diagnosis measured by FEV1 z-score was (i) significantly worse in individuals with CCDC39 mutations compared to other gene mutations and (ii) better in those with DNAH11 mutations; the latter also reported less neonatal respiratory distress. Patients without neonatal respiratory distress had better preserved FEV1 at diagnosis. Individuals with DNAH5 mutations were phenotypically diverse. Cilia ultrastructure and beat pattern defects correlated closely to specific causative gene groups, confirming these tests can be used to support a genetic diagnosis. /
Conclusions: This large scale multi-national study presents PCD as a syndrome with overlapping symptoms and variation in phenotype, according to genotype. TDA modelling confirmed genotype-phenotype relationships reported by smaller studies (e.g. FEV1 worse with CCDC39 mutations), and identified new relationships, including FEV1 preservation with DNAH11 mutations and diversity of severity with DNAH5 mutations
Proceedings of the 4th BEAT-PCD Conference and 5th PCD Training School
Primary ciliary dyskinesia (PCD) is an inherited ciliopathy leading to chronic suppurative lung disease, chronic rhinosinusitis, middle ear disease, sub-fertility and situs abnormalities. As PCD is rare, it is important that scientists and clinicians foster international collaborations to share expertise in order to provide the best possible diagnostic and management strategies. ‘Better Experimental Approaches to Treat Primary Ciliary Dyskinesia’ (BEAT-PCD) is a multidisciplinary network funded by EU COST Action (BM1407) to coordinate innovative basic science and clinical research from across the world to drive advances in the field. The fourth and final BEAT-PCD Conference and fifth PCD Training School were held jointly in March 2019 in Poznan, Poland. The varied program of plenaries, workshops, break-out sessions, oral and poster presentations were aimed to enhance the knowledge and skills of delegates, whilst also providing a collaborative platform to exchange ideas. In this final BEAT-PCD conference we were able to build upon programmes developed throughout the lifetime of the COST Action. These proceedings report on the conference, highlighting some of the successes of the BEAT-PCD programme
A search for resonant production of pairs in $4.8\ \rm{fb}^{-1}p\bar{p}\sqrt{s}=1.96\ \rm{TeV}$
We search for resonant production of tt pairs in 4.8 fb^{-1} integrated
luminosity of ppbar collision data at sqrt{s}=1.96 TeV in the lepton+jets decay
channel, where one top quark decays leptonically and the other hadronically. A
matrix element reconstruction technique is used; for each event a probability
density function (pdf) of the ttbar candidate invariant mass is sampled. These
pdfs are used to construct a likelihood function, whereby the cross section for
resonant ttbar production is estimated, given a hypothetical resonance mass and
width. The data indicate no evidence of resonant production of ttbar pairs. A
benchmark model of leptophobic Z \rightarrow ttbar is excluded with m_{Z'} <
900 GeV at 95% confidence level.Comment: accepted for publication in Physical Review D Sep 21, 201
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