2,634 research outputs found
Diagnosing Cysts With Correlation Coefficient Images From 2āDimensional Freehand Elastography
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135592/1/jum20072691201.pd
The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
Quasar emission lines are often shifted from the systemic velocity due to
various dynamical and radiative processes in the line-emitting region. The
level of these velocity shifts depends both on the line species and on quasar
properties. We study velocity shifts for the line peaks of various narrow and
broad quasar emission lines relative to systemic using a sample of 849 quasars
from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The
coadded (from 32 epochs) spectra of individual quasars have sufficient
signal-to-noise ratio (SNR) to measure stellar absorption lines to provide
reliable systemic velocity estimates, as well as weak narrow emission lines.
The sample also covers a large dynamic range in quasar luminosity (~2 dex),
allowing us to explore potential luminosity dependence of the velocity shifts.
We derive average line peak velocity shifts as a function of quasar luminosity
for different lines, and quantify their intrinsic scatter. We further quantify
how well the peak velocity can be measured for various lines as a function of
continuum SNR, and demonstrate there is no systematic bias in the line peak
measurements when the spectral quality is degraded to as low as SNR~3 per SDSS
pixel. Based on the observed line shifts, we provide empirical guidelines on
redshift estimation from [OII]3728, [OIII]5008, [NeV]3426, MgII, CIII],
HeII1640, broad Hbeta, CIV, and SiIV, which are calibrated to provide unbiased
systemic redshifts in the mean, but with increasing intrinsic uncertainties of
46, 56, 119, 205, 233, 242, 400, 415, and 477 km/s, in addition to the
measurement uncertainties. These more realistic redshift uncertainties are
generally much larger than the formal uncertainties reported by the redshift
pipelines for spectroscopic quasar surveys, and demonstrate the infeasibility
of measuring quasar redshifts to better than ~200 km/s with only broad lines.Comment: matched to the published version; minor changes and conclusions
unchange
The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
We explore the variability of quasars in the MgII and Hbeta broad emission
lines and UV/optical continuum emission using the Sloan Digital Sky Survey
Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic
study of quasar variability to date: our study includes 29 spectroscopic epochs
from SDSS-RM over months, containing 357 quasars with MgII and 41 quasars
with Hbeta . On longer timescales, the study is also supplemented with
two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional
quasars with MgII and 572 quasars with Hbeta. The MgII emission line is
significantly variable ( 10% on 100-day timescales), a necessary
prerequisite for its use for reverberation mapping studies. The data also
confirm that continuum variability increases with timescale and decreases with
luminosity, and the continuum light curves are consistent with a damped
random-walk model on rest-frame timescales of days. We compare the
emission-line and continuum variability to investigate the structure of the
broad-line region. Broad-line variability shows a shallower increase with
timescale compared to the continuum emission, demonstrating that the broad-line
transfer function is not a -function. Hbeta is more variable than MgII
(roughly by a factor of ), suggesting different excitation mechanisms,
optical depths and/or geometrical configuration for each emission line. The
ensemble spectroscopic variability measurements enabled by the SDSS-RM project
have important consequences for future studies of reverberation mapping and
black hole mass estimation of quasars.Comment: 20 pages, 25 figures. ApJ accepted: minor revisions following referee
repor
ThreeāDimensional Sonographic Measurement of Blood Volume Flow in the Umbilical Cord
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135361/1/jum201231121927.pd
The convergent roles of the nuclear factor I transcription factors in development and cancer
The nuclear factor I (NFI) transcription factors play important roles during normal development and have been associated with developmental abnormalities in humans. All four family members, NFIA, NFIB, NFIC and NFIX, have a homologous DNA binding domain and function by regulating cell proliferation and differentiation via the transcriptional control of their target genes. More recently, NFI genes have also been implicated in cancer based on genomic analyses and studies of animal models in a variety of tumours across multiple organ systems. However, the association between their functions in development and in cancer is not well described. In this review, we summarise the evidence suggesting a converging role for the NFI genes in development and cancer. Our review includes all cancer types in which the NFI genes are implicated, focusing predominantly on studies demonstrating their oncogenic or tumour suppressive potential. We conclude by presenting the challenges impeding our understanding of NFI function in cancer biology, and demonstrate how a developmental perspective may contribute towards overcoming such hurdles. (C) 2017 Elsevier B.V. All rights reserved
The Spectral Energy Distributions of Red 2MASS AGN
We present infrared (IR) to X-ray spectral energy distributions (SEDs) for 44
red AGN selected from the 2MASS survey on the basis of their red J-K color
(>2 mag) and later observed by Chandra. In comparison with optically-, radio-,
and X-ray selected AGN, their median SEDs are red in the optical and near-IR
with little/no blue bump. It thus seems that near-IR color selection isolates
the reddest subset of AGN that can be classified optically. The shape of the
SEDs is generally consistent with modest absorption by gas (in the X-ray) and
dust (in the optical-IR). The levels of obscuration, estimated from X-rays,
far-IR and our detailed optical/near-IR color modeling are all consistent
implying N_H < few*10^{22} cm^{-2}. We present SED models that show how the AGN
optical/near-IR colors change due to differing amounts of reddening, AGN to
host galaxy ratio, redshift and scattered light emission and apply them to the
sources in the sample. We find that the 2MASS AGN optical color, B-R, and to a
lesser extent the near-IR color, J-K, are strongly affected by reddening,
host galaxy emission, redshift, and in few, highly polarized objects, also by
scattered AGN light. The obscuration/inclination of the AGN allows us to see
weaker emission components which are generally swamped by the AGN.Comment: 52 pages, 17 figures, accepted for publication in Ap
Microbial infections in eight genomic subtypes of chronic fatigue syndrome/myalgic encephalomyelitis
Nondispersive hole transport in a spin-coated dendrimer film measured by the charge-generation-layer time-of-flight method
Published versio
What empirical research has been undertaken on the ethics of clinical research in India?:A systematic scoping review and narrative synthesis
IntroductionThe post-2005 rise in clinical trials and clinical research conducted in India was accompanied by frequent reports of unethical practices, leading to a series of regulatory changes. We conducted a systematic scoping review to obtain an overview of empirical research pertaining to the ethics of clinical trials/research in India.MethodsOur search strategy combined terms related to ethics/bioethics, informed consent, clinical trials/research and India, across nine databases, up to November 2019. Peer-reviewed research exploring ethical aspects of clinical trials/research in India with any stakeholder groups was included. We developed an evidence map, undertook a narrative synthesis and identified research gaps. A consultation exercise with stakeholders in India helped contextualise the review and identify additional research priorities.ResultsTitles/Abstracts of 9699 articles were screened, full text of 282 obtained and 80 were included. Research on the ethics of clinical trials/research covered a wide range of topics, often conducted with little to no funding. Studies predominantly examined what lay (patients/public) and professional participants (eg, healthcare staff/students/faculty) know about topics such as research ethics or understand from the information given to obtain their consent for research participation. Easily accessible groups, namely ethics committee members and healthcare students were frequently researched. Research gaps included developing a better understanding of the recruitment-informed consent process, including the doctor-patient interaction, in multiple contexts and exploring issues of equity and justice in clinical trials/research.ConclusionThe review demonstrates that while a wide range of topics have been studied in India, the focus is largely on assessing knowledge levels across different population groups. This is a useful starting point, but fundamental questions remain unanswered about informed consent processes and broader issues of inequity that pervade the clinical trials/research landscape. A priority-setting exercise and appropriate funding mechanisms to support researchers in India would help improve the clinical trials/research ecosystem
A wildland fire model with data assimilation
A wildfire model is formulated based on balance equations for energy and
fuel, where the fuel loss due to combustion corresponds to the fuel reaction
rate. The resulting coupled partial differential equations have coefficients
that can be approximated from prior measurements of wildfires. An ensemble
Kalman filter technique with regularization is then used to assimilate
temperatures measured at selected points into running wildfire simulations. The
assimilation technique is able to modify the simulations to track the
measurements correctly even if the simulations were started with an erroneous
ignition location that is quite far away from the correct one.Comment: 35 pages, 12 figures; minor revision January 2008. Original version
available from http://www-math.cudenver.edu/ccm/report
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