37 research outputs found
Gravitational Lensing
Gravitational lensing has developed into one of the most powerful tools for
the analysis of the dark universe. This review summarises the theory of
gravitational lensing, its main current applications and representative results
achieved so far. It has two parts. In the first, starting from the equation of
geodesic deviation, the equations of thin and extended gravitational lensing
are derived. In the second, gravitational lensing by stars and planets,
galaxies, galaxy clusters and large-scale structures is discussed and
summarised.Comment: Invited review article to appear in Classical and Quantum Gravity, 85
pages, 15 figure
Cluster Lenses
Clusters of galaxies are the most recently assembled, massive, bound
structures in the Universe. As predicted by General Relativity, given their
masses, clusters strongly deform space-time in their vicinity. Clusters act as
some of the most powerful gravitational lenses in the Universe. Light rays
traversing through clusters from distant sources are hence deflected, and the
resulting images of these distant objects therefore appear distorted and
magnified. Lensing by clusters occurs in two regimes, each with unique
observational signatures. The strong lensing regime is characterized by effects
readily seen by eye, namely, the production of giant arcs, multiple-images, and
arclets. The weak lensing regime is characterized by small deformations in the
shapes of background galaxies only detectable statistically. Cluster lenses
have been exploited successfully to address several important current questions
in cosmology: (i) the study of the lens(es) - understanding cluster mass
distributions and issues pertaining to cluster formation and evolution, as well
as constraining the nature of dark matter; (ii) the study of the lensed objects
- probing the properties of the background lensed galaxy population - which is
statistically at higher redshifts and of lower intrinsic luminosity thus
enabling the probing of galaxy formation at the earliest times right up to the
Dark Ages; and (iii) the study of the geometry of the Universe - as the
strength of lensing depends on the ratios of angular diameter distances between
the lens, source and observer, lens deflections are sensitive to the value of
cosmological parameters and offer a powerful geometric tool to probe Dark
Energy. In this review, we present the basics of cluster lensing and provide a
current status report of the field.Comment: About 120 pages - Published in Open Access at:
http://www.springerlink.com/content/j183018170485723/ . arXiv admin note:
text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author
Unbound Particles in Dark Matter Halos
We investigate unbound dark matter particles in halos by tracing particle
trajectories in a simulation run to the far future (a = 100). We find that the
traditional sum of kinetic and potential energies is a very poor predictor of
which dark matter particles will eventually become unbound from halos. We also
study the mass fraction of unbound particles, which increases strongly towards
the edges of halos, and decreases significantly at higher redshifts. We discuss
implications for dark matter detection experiments, precision calibrations of
the halo mass function, the use of baryon fractions to constrain dark energy,
and searches for intergalactic supernovae.Comment: Significant improvements following referee suggestion
Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk
BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7Ă10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4Ă10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4Ă10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat
Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic.
Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality.
Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States.
Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis.
Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection
Core or Cusps: The Central Dark Matter Profile of a Strong Lensing Cluster with a Bright Central Image at Redshift 1
Development and Evaluation of a Decision Aid for BRCA Carriers with Breast Cancer
An explorative study of an image retrieval interface with
respect to the support it offers the user to organise their search results is presented. The evaluation, involving design professionals performing practical and relevant tasks, shows that the proposed approach succeeds in encouraging the user to conceptualise their tasks better
The Power of Partnership: Extending Comprehensive Cancer Center Expertise in Clinical Cancer Genetics to Community Breast Care Centers
PS1-12sk is a Peculiar Supernova From a He-rich Progenitor System in a Brightest Cluster Galaxy Environment
We report on our discovery and observations of the Pan-STARRS1 supernova (SN)
PS1-12sk, a transient with properties that indicate atypical star formation in
its host galaxy cluster or pose a challenge to popular progenitor system models
for this class of explosion. The optical spectra of PS1-12sk classify it as a
Type Ibn SN (c.f. SN 2006jc), dominated by intermediate-width (3x10^3 km/s) and
time variable He I emission. Our multi-wavelength monitoring establishes the
rise time dt = 9-23 days and shows an NUV-NIR SED with temperature > 17x10^3 K
and a peak rise magnitude of Mz = -18.9 mag. SN Ibn spectroscopic properties
are commonly interpreted as the signature of a massive star (17 - 100 M_sun)
explosion within a He-enriched circumstellar medium. However, unlike previous
Type Ibn supernovae, PS1-12sk is associated with an elliptical brightest
cluster galaxy, CGCG 208-042 (z = 0.054) in cluster RXC J0844.9+4258. The
expected probability of an event like PS1-12sk in such environments is low
given the measured infrequency of core-collapse SNe in red sequence galaxies
compounded by the low volumetric rate of SN Ibn. Furthermore, we find no
evidence of star formation at the explosion site to sensitive limits (Sigma
Halpha < 2x10^-3 M_sun/yr/kpc^2). We therefore discuss white dwarf binary
systems as a possible progenitor channel for SNe Ibn. We conclude that PS1-12sk
represents either a fortuitous and statistically unlikely discovery, evidence
for a top-heavy IMF in galaxy cluster cooling flow filaments, or the first clue
suggesting an alternate progenitor channel for Type Ibn SNe.Comment: 16 pages, 9 figures, v2 as accepted by ApJ, more information at
http://www.cfa.harvard.edu/~nsanders/papers/12sk/summary.ht
The Burden of Breast Cancer Predisposition Variants Across The Age Spectrum Among 10 000 Patients.
BACKGROUND/OBJECTIVES: Women diagnosed with breast cancer (BC) at an older age are less likely to undergo genetic cancer risk assessment and genetic testing since the guidelines and referrals are biased toward earlier age at diagnosis. Thus, we determined the prevalence and type of pathogenic cancer predisposition variants among women with a history of BC diagnosed at the ageâof 65 years or older vs younger than 65âyears.
DESIGN: Prospective registration cohort.
SETTING: The Clinical Cancer Genomics Community Research Network, including 40 community-based clinics in the United States and 5 in Latin America.
PARTICIPANTS: Women with BC and genetic testing results.
MEASUREMENTS: Sociodemographic characteristics, clinical variables, and genetic profiles were compared between women aged 65 years and older andâthose younger than 65âyears at BC diagnosis.
RESULTS: Among 588 women diagnosed with BC and aged 65âyears and older and 9412 diagnosed at younger than 65âyears, BC-associated pathogenic variants (PVs) were detected in 5.6% of those aged 65 years and older (nâ=â33) and 14.2% of those younger than 65âyears (nâ=â1340) (Pâ\u3câ.01). PVs in high-risk genes (eg, BRCA1 and BRCA2) represented 81.1% of carriers among women aged 65âyears and older (nâ=â27) and 93.1% of those younger than 65âyears (nâ=â1248) (Pâ=â.01). BRCA2 PVs represented 42.4% of high-risk gene findings for those aged 65âyears and older, whereas BRCA1 PVs were most common among carriers younger than 65âyears (49.7%). PVs (nâ=â7) in moderate-risk genes represented 21.2% for carriers aged 65 years and older and 7.3% of those younger than 65 years (nâ=â98; Pâ\u3câ.01). CHEK2 PVs were the most common moderate-risk gene finding in both groups.
CONCLUSION: Clinically actionable BC susceptibility PVs, particularly in BRCA2 and CHEK2, were relatively prevalent among older women undergoing genetic testing. The significant burden of PVs for older women with BC provides a critical reminder to recognize the full spectrum of eligibility and provide genetic testing for older women, rather than exclusion based on chronological age alone. J Am Geriatr Soc 67:884-888, 2019