309 research outputs found
Review and test of the Naperville, Illinois, electrical light plant
Thesis (BS)--University of Illinois, 1906TypescriptIncludes bibliographical reference
Phase imaging systems for measurement of plasma density contours
During recent years, there has been considerable interest in obtaining spatially localized time resolved density measurements in fusion plasmas. However, the study of such phenomena requires many channels of information on a scale much finer than available with current discrete chordal view multichannel interferometers. These problems can be overcome by imaging an expanded probe beam occupying the entire plasma port crosssection onto a linear detector array [1], thereby significantly reducing the number of optical components and hence the cost and complexity of the system compared with a comparable discrete chord multichannel interferometer. Other more fundamental advantages of the imaging technique include compensation for phase errors due to plasma refraction, whilst the diffraction limited system resolution (typically ≃ 1cm for FIR probe wavelengths) allows the use of many detector channels for high spatial sampling rates. and hence accurate reconstruction of the density profiles
The role of DNA damage response pathways in chromosome fragility in Fragile X syndrome
FRAXA is one of a number of fragile sites in human chromosomes that are induced by agents like fluorodeoxyuridine (FdU) that affect intracellular thymidylate levels. FRAXA coincides with a >200 CGG•CCG repeat tract in the 5′ UTR of the FMR1 gene, and alleles prone to fragility are associated with Fragile X (FX) syndrome, one of the leading genetic causes of intellectual disability. Using siRNA depletion, we show that ATR is involved in protecting the genome against FdU-induced chromosome fragility. We also show that FdU increases the number of γ-H2AX foci seen in both normal and patient cells and increases the frequency with which the FMR1 gene colocalizes with these foci in patient cells. In the presence of FdU and KU55933, an ATM inhibitor, the incidence of chromosome fragility is reduced, suggesting that ATM contributes to FdU-induced chromosome fragility. Since both ATR and ATM are involved in preventing aphidicolin-sensitive fragile sites, our data suggest that the lesions responsible for aphidicolin-induced and FdU-induced fragile sites differ. FRAXA also displays a second form of chromosome fragility in absence of FdU, which our data suggest is normally prevented by an ATM-dependent process
Detection of a Distinct Pseudobulge Hidden Inside the "Box-Shaped Bulge" of NGC 4565
N-body simulations show that "box-shaped bulges" of edge-on galaxies are not
bulges at all: they are bars seen side-on. The two components that we readily
see in edge-on Sb galaxies like NGC 4565 are a disk and a bar, but face-on SBb
galaxies always show a disk, a bar, and a (pseudo)bulge. Where is the
(pseudo)bulge in NGC 4565? We use archival Hubble Space Telescope K-band and
Spitzer Space Telescope 3.6 um images to penetrate the dust in NGC 4565. We
find a high surface brightness, central stellar component, distinct from the
boxy bar and from the galaxy's disk. Its minor-axis profile has a Sersic index
of 1.33+/-0.12, so it is a pseudobulge. The pseudobulge has the smallest scale
height (~90 pc) of any component in the galaxy, in contrast to ~740 pc for the
boxy bar plus thin disk. The disky pseudobulge is also much less luminous than
the boxy bar, so the true (pseudo)bulge-to-total luminosity ratio of the galaxy
is much less than previously thought. We infer that the pseudobulge-to-total
luminosity ratios of edge-on galaxies with box-shaped bulges have generally
been overestimated. Therefore more galaxies than we have recognized contain
little or no evidence of a merger-built classical bulge. This challenges our
picture of galaxy formation by hierarchical clustering, because it is difficult
to grow big galaxies without also making a big classical bulge. Solving the
puzzle of the "missing pseudobulge" in NGC 4565 further increases our
confidence that we understand box-shaped bulges correctly as edge-on bars. This
supports our developing picture of the formation of pseudobulges -- both
edge-on bars and disky central components -- by secular evolution in isolated
galaxies.Comment: 5 pages, 3 figures, requires asp2006.sty, to be published in Galaxy
Evolution: Emerging Insights and Future Challenges, ed. S. Jogee et al.,
Astron. Soc. Pacific, 200
Optical BVI Imaging and HI Synthesis Observations of the Dwarf Irregular Galaxy ESO 364-G 029
As part of an effort to enlarge the number of well-studied Magellanic-type
galaxies, we obtained broadband optical imaging and neutral hydrogen radio
synthesis observations of the dwarf irregular galaxy ESO 364-G 029. The optical
morphology characteristically shows a bar-like main body with a one-sided
spiral arm, an approximately exponential light distribution, and offset
photometric and kinematic centers. The HI distribution is mildly asymmetric
and, although slightly offset from the photometric center, roughly follows the
optical brightness distribution, extending to over 1.2 Holmberg radii (where
mu_B = 26.5 mag/arcsec^2). In particular, the highest HI column densities
closely follow the bar, one-arm spiral, and a third optical extension. The
rotation is solid-body in the inner parts but flattens outside of the optical
extent. The total HI flux F_HI = 23.1 pm 1.2 Jy km/s, yielding a total HI mass
M_HI= (6.4 pm 1.7) x 10^8 Msun (for a distance D = 10.8 pm 1.4 Mpc) and a total
HI mass-to-blue-luminosity ratio M_HI/L_B = (0.96 pm 0.14) Msun / Lsun,B
(distance independent). The HI data suggest a very complex small-scale HI
structure, with evidence of large shells and/or holes, but deeper observations
are required for a detailed study. Follow-up observations are also desirable
for a proper comparison with the Large Magellanic Cloud, where despite an
optical morphology very similar to ESO 364-G 029 the HI bears little
resemblance to the optical.Comment: 10 pages, 11 figures, accepted by A&
Bostonia: The Boston University Alumni Magazine. Volume 9
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
HI in very metal-poor galaxies: the SBS 0335-052 system
We present Giant Metrewave Radio Telescope (GMRT), HI 21cm observations of
SBS 0335-052E and SBS 0335-052W, a close pair of dwarf galaxies, which are
further unusual in being the most metal-poor star-forming galaxies known. We
present images at several angular resolutions, ranging from ~40 to 4 arcsec.
These images show that SBS 0335-052 is a strongly interacting system, with a
faint diffuse HI bridge seen at low resolution, and elongated tails seen at the
higher resolutions. The overall morphology suggests that the pair represents a
major merger of extremely gas-rich galaxies. The low-resolution velocity field
is dominated by the velocity difference between the two galaxies and the
velocity gradient along the tidal features. However, for SBS 0335-052W at
least, at high angular resolution, one sees a central velocity field that could
be associated with the spin of the original undisturbed disc. The highest
angular resolution HI images show that the ionized superbubble, identified by
Thuan, Izotov & Lipovetsky (1997), in the Hubble Space Telescope (HST) images
of SBS 0335-052E, is extended along one of the diffuse tidal features, and that
there is a high-density HI clump at the other end of the superbubble. The star
formation in SBS 0335-052E occurs mainly in a group of superstar clusters
(SSCs) with a clear age gradient; the age decreases as one approaches the dense
HI clump. We suggest that this propagating star formation is driven by the
superbubble expanding into a medium with a tidally-produced density gradient.
The high pressures associated with the compressed material would also naturally
explain why current star formation is mainly concentrated in superstar
clusters.Comment: Accepted for publication in MNRA
inv(8)(p11.2q13) found in a patient with chronic myelomonocytic leukemia that progressed to acute myeloid leukemia
Stochastic Gravity: Theory and Applications
Whereas semiclassical gravity is based on the semiclassical Einstein equation
with sources given by the expectation value of the stress-energy tensor of
quantum fields, stochastic semiclassical gravity is based on the
Einstein-Langevin equation, which has in addition sources due to the noise
kernel. In the first part, we describe the fundamentals of this new theory via
two approaches: the axiomatic and the functional. In the second part, we
describe three applications of stochastic gravity theory. First, we consider
metric perturbations in a Minkowski spacetime, compute the two-point
correlation functions of these perturbations and prove that Minkowski spacetime
is a stable solution of semiclassical gravity. Second, we discuss structure
formation from the stochastic gravity viewpoint. Third, we discuss the
backreaction of Hawking radiation in the gravitational background of a black
hole and describe the metric fluctuations near the event horizon of an
evaporating black holeComment: 100 pages, no figures; an update of the 2003 review in Living Reviews
in Relativity gr-qc/0307032 ; it includes new sections on the Validity of
Semiclassical Gravity, the Stability of Minkowski Spacetime, and the Metric
Fluctuations of an Evaporating Black Hol
The DESiGN trial (DEtection of Small for Gestational age Neonate), evaluating the effect of the Growth Assessment Protocol (GAP): study protocol for a randomised controlled trial.
BACKGROUND: Stillbirth rates in the United Kingdom (UK) are amongst the highest of all developed nations. The association between small-for-gestational-age (SGA) foetuses and stillbirth is well established, and observational studies suggest that improved antenatal detection of SGA babies may halve the stillbirth rate. The Growth Assessment Protocol (GAP) describes a complex intervention that includes risk assessment for SGA and screening using customised fundal-height growth charts. Increased detection of SGA from the use of GAP has been implicated in the reduction of stillbirth rates by 22%, in observational studies of UK regions where GAP uptake was high. This study will be the first randomised controlled trial examining the clinical efficacy, health economics and implementation of the GAP programme in the antenatal detection of SGA. METHODS/DESIGN: In this randomised controlled trial, clusters comprising a maternity unit (or National Health Service Trust) were randomised to either implementation of the GAP programme, or standard care. The primary outcome is the rate of antenatal ultrasound detection of SGA in infants found to be SGA at birth by both population and customised standards, as this is recognised as being the group with highest risk for perinatal morbidity and mortality. Secondary outcomes include antenatal detection of SGA by population centiles, antenatal detection of SGA by customised centiles, short-term maternal and neonatal outcomes, resource use and economic consequences, and a process evaluation of GAP implementation. Qualitative interviews will be performed to assess facilitators and barriers to implementation of GAP. DISCUSSION: This study will be the first to provide data and outcomes from a randomised controlled trial investigating the potential difference between the GAP programme compared to standard care for antenatal ultrasound detection of SGA infants. Accurate information on the performance and service provision requirements of the GAP protocol has the potential to inform national policy decisions on methods to reduce the rate of stillbirth. TRIAL REGISTRATION: Primary registry and trial identifying number: ISRCTN 67698474 . Registered on 2 November 2016
- …