659 research outputs found
The Effect of Severe Intraventricular Hemorrhage on the Biorhythms of Feeding in Premature Infants
Background: Suck-swallow rhythmicity and the integration of breathing into infant feeding are developmentally regulated. Neurological injury and breathing abnormalities can both impact feeding in preterm infants.
Objective: To determine the effects of neurologic injury independent of effects of disordered breathing on feeding biorhythms in premature infants.
Methods: Low-risk preterm infants (LRP), infants with Grade 3–4 Intraventricular Hemorrhage (IVH), those with bronchopulmonary dysplasia (BPD), and those with both BPD and IVH (BPD+IVH) were identified. Forty-seven infants, 32–42 weeks Postmenstrual Age (PMA) were evaluated on one or more occasions (131 studies). Of these, 39 infants (81 studies) were performed at \u3e35 weeks PMA. Coefficient of variation (COV) (=standard deviation of the inter-event (e.g., suck-suck, swallow-breath, etc.) interval divided by the mean of the interval) was used to quantify rhythmic stability.
Results: To adjust for PMA, only those infants \u3e35–42 weeks were compared. Suck-suck COV was significantly lower (more rhythmically stable) in the LRP group [COV = 0.274 ± 0.051 (S.D.)] compared to all other groups (BPD = 0.325 ± 0.066; IVH = 0.342 ± 0.072; BPD + IVH = 0.314 ± 0.069; all p \u3c 0.05). Similarly, suck-swallow COV was significantly lower in LRP babies (0.360 ± 0.066) compared to the BPD group (0.475 ± 0.113) and the IVH cohort (0.428 ± 0.075) (p \u3c 0.05). The BPD+IVH group (0.424 ± 0.109), while higher, was not quite statistically significant.
Conclusions: Severe IVH negatively impacts suck-suck and suck-swallow rhythms. The independent effect of neurological injury in the form of IVH on feeding rhythms suggests that quantitative analysis of feeding may reflect and predict neurological sequelae
NuSTAR study of Hard X-Ray Morphology and Spectroscopy of PWN G21.5-0.9
We present NuSTAR high energy X-ray observations of the pulsar wind nebula
(PWN)/supernova remnant G21.5-0.9. We detect integrated emission from the
nebula up to ~40 keV, and resolve individual spatial features over a broad
X-ray band for the first time. The morphology seen by NuSTAR agrees well with
that seen by XMM-Newton and Chandra below 10 keV. At high energies NuSTAR
clearly detects non-thermal emission up to ~20 keV that extends along the
eastern and northern rim of the supernova shell. The broadband images clearly
demonstrate that X-ray emission from the North Spur and Eastern Limb results
predominantly from non-thermal processes. We detect a break in the spatially
integrated X-ray spectrum at ~9 keV that cannot be reproduced by current SED
models, implying either a more complex electron injection spectrum or an
additional process such as diffusion compared to what has been considered in
previous work. We use spatially resolved maps to derive an energy-dependent
cooling length scale, with . We find
this to be inconsistent with the model for the morphological evolution with
energy described by Kennel & Coroniti (1984). This value, along with the
observed steepening in power-law index between radio and X-ray, can be
quantitatively explained as an energy-loss spectral break in the simple scaling
model of Reynolds (2009), assuming particle advection dominates over diffusion.
This interpretation requires a substantial departure from spherical
magnetohydrodynamic (MHD), magnetic-flux-conserving outflow, most plausibly in
the form of turbulent magnetic-field amplification.Comment: 13 pages, 8 figures, 1 table, Accepted for publication in the
Astrophysical Journa
An X-Ray View of the Jet-Cycle in the Radio Loud AGN 3C120
We present a study of the central engine in the broad-line radio galaxy 3C120
using a multi-epoch analysis of a deep XMM-Newton observation and two deep
Suzaku pointings (in 2012). In order to place our spectral data into the
context of the disk-disruption/jet-ejection cycles displayed by this object, we
monitor the source in the UV/X-ray bands, and in the radio band. We find three
statistically acceptable spectral models, a disk-reflection model, a jet-model
and a jet+disk model. Despite being good descriptions of the data, the
disk-reflection model violates the radio constraints on the inclination, and
the jet-model has a fine-tuning problem, requiring a jet contribution exceeding
that expected. Thus, we argue for a composite jet+disk model. Within the
context of this model, we verify the basic predictions of the jet-cycle
paradigm, finding a truncated/refilling disk during the Suzaku observations and
a complete disk extending down to the innermost stable circular orbit (ISCO)
during the XMM-Newton observation. The idea of a refilling disk is further
supported by the detection of the ejection of a new jet knot approximately one
month after the Suzaku pointings. We also discover a step-like event in one of
the Suzaku pointings in which the soft band lags the hard band. We suggest that
we are witnessing the propagation of a disturbance from the disk into the jet
on a timescale set by the magnetic field.Comment: 14 pages, 10 figures, accepted for publication in Ap
Comparative transcriptomic analysis of Porphyromonas gingivalis biofilm and planktonic cells
<p>Abstract</p> <p>Background</p> <p><it>Porphyromonas gingivalis </it>in subgingival dental plaque, as part of a mature biofilm, has been strongly implicated in the onset and progression of chronic periodontitis. In this study using DNA microarray we compared the global gene expression of a <it>P. gingivalis </it>biofilm with that of its planktonic counterpart grown in the same continuous culture.</p> <p>Results</p> <p>Approximately 18% (377 genes, at 1.5 fold or more, <it>P</it>-value < 0.01) of the <it>P. gingivalis </it>genome was differentially expressed when the bacterium was grown as a biofilm. Genes that were down-regulated in biofilm cells, relative to planktonic cells, included those involved in cell envelope biogenesis, DNA replication, energy production and biosynthesis of cofactors, prosthetic groups and carriers. A number of genes encoding transport and binding proteins were up-regulated in <it>P. gingivalis </it>biofilm cells. Several genes predicted to encode proteins involved in signal transduction and transcriptional regulation were differentially regulated and may be important in the regulation of biofilm growth.</p> <p>Conclusion</p> <p>This study analyzing global gene expression provides insight into the adaptive response of <it>P. gingivalis </it>to biofilm growth, in particular showing a down regulation of genes involved in growth and metabolic activity.</p
Autonomic Nervous System Function Following Prenatal Opiate Exposure
In utero exposure to opiates may affect autonomic functioning of the fetus and newborn. We investigated heart rate variability (HRV) as a measure of autonomic stability in prenatal opiate-exposed neonates (n = 14) and in control term infants (n = 10). Electrocardiographic data during both non-nutritive and nutritive sucking were evaluated for RR intervals, heart rate (HR), standard deviation of the consecutive RR intervals (SDRR), standard deviation of the differences of consecutive RR intervals (SDDRR), and the power spectral densities in low and high frequency bands. In controls, mean HR increased significantly, 143-161 per min (p = 0.002), with a trend toward a decrease in RR intervals from non-nutritive to nutritive sucking; these measures did not change significantly among exposed infants. Compared to controls, exposed infants demonstrated significantly greater HRV or greater mean SDRR and SDDRR during non-nutritive period (p \u3c 0.01), greater mean SDDRR during nutritive sucking (p = 0.02), and higher powers in the low and high frequency bands during nutritive feedings. Our findings suggest that prenatal opiate exposure may be associated with changes in autonomic nervous system (ANS) functioning involving both sympathetic and parasympathetic branches. Future studies are needed to examine the effects of prenatal opiate exposure on ANS function
The high-speed X-ray camera on AXIS
AXIS is a Probe-class mission concept that will provide high-throughput,
high-spatial-resolution X-ray spectral imaging, enabling transformative studies
of high-energy astrophysical phenomena. To take advantage of the advanced
optics and avoid photon pile-up, the AXIS focal plane requires detectors with
readout rates at least 20 times faster than previous soft X-ray imaging
spectrometers flying aboard missions such as Chandra and Suzaku, while
retaining the low noise, excellent spectral performance, and low power
requirements of those instruments. We present the design of the AXIS high-speed
X-ray camera, which baselines large-format MIT Lincoln Laboratory CCDs
employing low-noise pJFET output amplifiers and a single-layer polysilicon gate
structure that allows fast, low-power clocking. These detectors are combined
with an integrated high-speed, low-noise ASIC readout chip from Stanford
University that provides better performance than conventional discrete
solutions at a fraction of their power consumption and footprint. Our
complementary front-end electronics concept employs state of the art digital
video waveform capture and advanced signal processing to deliver low noise at
high speed. We review the current performance of this technology, highlighting
recent improvements on prototype devices that achieve excellent noise
characteristics at the required readout rate. We present measurements of the
CCD spectral response across the AXIS energy band, augmenting lab measurements
with detector simulations that help us understand sources of charge loss and
evaluate the quality of the CCD backside passivation technique. We show that
our technology is on a path that will meet our requirements and enable AXIS to
achieve world-class science.Comment: 17 pages, 11 figures, submitted to Proceedings of SPIE Optics +
Photonics 202
A Search for Molecular Gas in the Nucleus of M87 and Implications for the Fueling of Supermassive Black Holes
Supermassive black holes in giant elliptical galaxies are remarkably faint
given their expected accretion rates. This motivates models of radiatively
inefficient accretion, due to either ion-electron thermal decoupling,
generation of outflows that inhibit accretion, or settling of gas to a
gravitationally unstable disk that forms stars in preference to feeding the
black hole. The latter model predicts the presence of cold molecular gas in a
thin disk around the black hole. Here we report Submillimeter Array
observations of the nucleus of the giant elliptical galaxy M87 that probe 230
GHz continuum and CO(J=2--1) line emission. Continuum emission is detected from
the nucleus and several knots in the jet, including one that has been
undergoing flaring behavior. We estimate a conservative upper limit on the mass
of molecular gas within ~100pc and +-400km/s line of sight velocity of the
central black hole of ~8x10^6Msun, which includes an allowance for possible
systematic errors associated with subtraction of the continuum. Ignoring such
errors, we have a 3 sigma sensitivity to about 3x10^6Msun. In fact, the
continuum-subtracted spectrum shows weak emission features extending up to 4
sigma above the RMS dispersion of the line-free channels. These may be
artifacts of the continuum subtraction process. Alternatively, if they are
interpreted as CO emission, then the implied molecular gas mass is ~5x10^6Msun
spread out over a velocity range of 700km/s. These constraints on molecular gas
mass are close to the predictions of the model of self-gravitating,
star-forming accretion disks fed by Bondi accretion (Tan & Blackman 2005).Comment: 10 pages, accepted to ApJ Main Journa
Vision 2020: A View of Our Energy Future
The Morning Address was given by The Honorable George Allen.
“The Regulatory Framework: Where Are We Headed?” session by Eric Finkbeiner, Senior Adviser for Policy, Office of Governor Robert McDonnell; David Christian, Chief Executive Officer, Dominion Generation; and Professor Joel Eisen, University of Richmond School of Law. Professor Noah Sachs, University of Richmond School of Law, served as moderator.
“The Future of Coal” session by John Lain, Partner at McGuireWoods LLP; Cale Jaffe, Senior Attorney with the Southern Environmental Law Center; and W. Thomas Hudson, President of W. Thomas Hudson and Associates, Inc. and of the Virginia Coal Association. Stephen E. Taylor, Allen Chair Editor for the University of Richmond Law Review, served as moderator.
“Nuclear Power: Is There a ‘Renaissance’?” session by Donald Irwin, Hunton & Williams; Christopher Paine, Director of Nuclear Program, Natural Resources Defense Council (invited); and Michael H. Montgomery, Vice President of Fuel Development, Lightbridge Corporation. Tricia Dunlap, Robert R. Merhige, Jr. Fellow at the University of Richmond School of Law, served as moderator.
“Emerging Issues in Energy Policy” session by Mark Rosen, Deputy General Counsel, CNA Corporation; Jefferson Reynolds, Water Policy Director with the Virginia Department of Environmental Quality; Kruskaia Sierra-Escalante, Senior Counsel for the International Finance Corporation; and Edward Lowe, General Manager for Renewable Energy Market Development, GE Energy. Andrea W. Wortzel, Counsel with Hunton & Williams and Vice Chair of the Environmental Law Section of the Virginia State Bar, served as moderator.
The Closing Address was given by The Honorable Carol M. Browner, Assistant to the President for Energy and Climate Change and Former Administrator of the Environmental Protection Agency (invited)
The Far-Infrared Spectral Energy Distributions of X-ray-selected Active Galaxies
[Abridged] We present ISO far-infrared (IR) observations of 21 hard X-ray
selected AGN from the HEAO-1 A2 sample. We compare the far-IR to X-ray spectral
energy distributions (SEDs) of this sample with various radio and optically
selected AGN samples. The hard-X-ray selected sample shows a wider range of
optical/UV shapes extending to redder near-IR colors. The bluer objects are
Seyfert 1s, while the redder AGN are mostly intermediate or type 2 Seyferts.
This is consistent with a modified unification model in which the amount of
obscuring material increases with viewing angle and may be clumpy. Such a
scenario, already suggested by differing optical/near-IR spectroscopic and
X-ray AGN classifications, allows for different amounts of obscuration of the
continuum emission in different wavebands and of the broad emission line region
which results in a mixture of behaviors for AGN with similar optical emission
line classifications. The resulting limits on the column density of obscuring
material through which we are viewing the redder AGN are 100 times lower than
for the standard optically thick torus models. The resulting decrease in
optical depth of the obscuring material allows the AGN to heat more dust at
larger radial distances. We show that an AGN-heated, flared, dusty disk with
mass 10^9 solar and size of few hundred pc is able to generate optical-far-IR
SEDs which reproduce the wide range of SEDs present in our sample with no need
for an additional starburst component to generate the long-wavelength, cooler
part of the IR continuum.Comment: 40 pages, 14 figures, accepted for publication in Astrophysical
Journal, V. 590, June 10, 200
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Adaptive migratory orientation of an invasive pest on a new continent
Many species of insects undertake long-range, seasonally reversed migrations, displaying sophisticated orientation behaviors to optimize their migratory trajectories. However, when invasive insects arrive in new biogeographical regions, it is unclear if migrants retain (or how quickly they regain) ancestral migratory traits, such as seasonally preferred flight headings. Here we present behavioral evidence that an invasive migratory pest, the fall armyworm moth (Spodoptera frugiperda), a native of the Americas, exhibited locally adaptive migratory orientation less than three years after arriving on a new continent. Specimens collected from China showed flight orientations directed north-northwest in spring and southwest in autumn, and this would promote seasonal forward and return migrations in East Asia. We also show that the driver of the seasonal switch in orientation direction is photoperiod. Our results thus provide a clear example of an invasive insect that has rapidly exhibited adaptive migratory behaviors, either inherited or newly evolved, in a completely alien environment
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