924 research outputs found
Constraining Radio Emission from Magnetars
We report on radio observations of five magnetars and two magnetar candidates
carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data
from these observations were searched for periodic emission and bright single
pulses. Also, monitoring observations of magnetar 4U0142+61 following its 2006
X-ray bursts were obtained. No radio emission was detected was detected for any
of our targets. The non-detections allow us to place luminosity upper limits
(at 1950 MHz) of approximately L < 1.60 mJy kpc^2 for periodic emission and L <
7.6 Jy kpc^2 for single pulse emission. These are the most stringent limits yet
for the magnetars observed. The resulting luminosity upper limits together with
previous results are discussed, as is the importance of further radio
observations of radio-loud and radio-quiet magnetars.Comment: 11 pages, 4 figure
On the Extended Emission Around the Anomalous X-ray Pulsar 1E 1547.0-5408
We present an analysis of the extended emission around the anomalous X-ray
pulsar 1E 1547.0-5408 using four XMM-Newton observations taken with the source
in varying states of outburst as well as in quiescence. We find that the
extended emission flux is highly variable and strongly correlated with the flux
of the magnetar. Based on this result, as well as on spectral and energetic
considerations, we conclude that the extended emission is dominated by a
dust-scattering halo and not a pulsar wind nebula (PWN), as has been previously
argued. We obtain an upper limit on the 2-10 keV flux of a possible PWN of
4.7e-14 erg/s/cm^2, three times less than the previously claimed value,
implying an efficiency for conversion of spin-down energy into nebular
luminosity of <9e-4 (assuming a distance of 4 kpc). We do, however, find strong
evidence for X-ray emission from the supernova remnant shell surrounding the
pulsar, as previously reported.Comment: 16 pages, 3 tables, 4 figures, published in the Astrophysical Journa
Detailed high-energy characteristics of AXP 4U 0142+61: Multi-year observations with INTEGRAL, RXTE, XMM-Newton, and ASCA
A study of 315 glitches in the rotation of 102 pulsars
The rotation of more than 700 pulsars has been monitored using the 76-m
Lovell Telescope at Jodrell Bank. Here we report on a new search for glitches
in the observations, revealing 128 new glitches in the rotation of 63 pulsars.
Combining these new data with those already published we present a database
containing 315 glitches in 102 pulsars. The database was used to study the
glitch activity among the pulsar population, finding that it peaks for pulsars
with a characteristic age tau_c ~ 10kyr and decreases for longer values of
tau_c, disappearing for objects with tau_c > 20Myr. The glitch activity is also
smaller in the very young pulsars (tau_c <~ 1kyr). The cumulative effect of
glitches, a collection of instantaneous spin up events, acts to reduce the
regular long term spindown rate |nudot| of the star. The percentage of |nudot|
reversed by glitch activity was found to vary between 0.5% and 1.6% for pulsars
with spindown rates |nudot| between 10^(-14) and 3.2*10^(-11) Hz/s, decreasing
to less than 0.01% at both higher and lower spindown rates. These ratios are
interpreted in terms of the amount of superfluid involved in the generation of
glitches. In this context the activity of the youngest pulsar studied, the Crab
pulsar, may be explained by quake-like activity within the crust. Pulsars with
low spindown rates seem to exhibit mostly small glitches, matching well the
decrease of their crustal superfluid.
Through the analysis of glitch sizes it was found that the particular
glitching behaviour of PSR J0537-6910 and the Vela pulsar may be shared by most
Vela-like pulsars. These objects present most of their glitches with
characteristic frequency and frequency derivative jumps, occurring at regular
intervals of time. Their behaviour is different from other glitching pulsars of
similar characteristic age.Comment: 26 pages, 17 figures, 6 tables. Accepted for publication in MNRA
A comparative study between shielded and open coplanar waveguide discontinuities
A comparative study between open and shielded coplanar waveguide (CPW) discontinuities is presented. The space domain integral equation method is used to characterize several discontinuities such as the open-end CPW and CPW series stubs. Two different geometries of CPW series stubs (straight and bent stubs) are compared with respect to resonant frequency and radiation loss. In addition, the encountered radiation loss due to different CPW shunt stubs is evaluated experimentally. The notion of forced radiation simulation is presented, and the results of such a simulation are compared to the actual radiation loss obtained rigorously. It is shown that such a simulation cannot give reliable results concerning radiation loss from printed circuits
Cell Therapy for Cardiovascular Disease: A Comparison of Methods of Delivery
The field of myocardial regeneration utilizing novel cell-based therapies, gene transfer, and growth factors may prove to play an important role in the future management of ischemic heart disease and cardiomyopathy. Phases I and II clinical trials have been published for a variety of biologics utilizing four methods of delivery: systemic infusion, intracoronary infusion, transvenous coronary sinus, and intramyocardial. This review discusses the advantages and disadvantages of the delivery approaches above
The Fine-Scale Structure of the neutral Interstellar Medium in nearby Galaxies
We present an analysis of the properties of HI holes detected in 20 galaxies
that are part of "The HI Nearby Galaxy Survey" (THINGS). We detected more than
1000 holes in total in the sampled galaxies. Where they can be measured, their
sizes range from about 100 pc (our resolution limit) to about 2 kpc, their
expansion velocities range from 4 to 36 km/s, and their ages are estimated to
range between 3 and 150 Myr. The holes are found throughout the disks of the
galaxies, out to the edge of the HI; 23% of the holes fall outside R25. We find
that shear limits the age of holes in spirals (shear is less important in dwarf
galaxies) which explains why HI holes in dwarfs are rounder, on average than in
spirals. Shear, which is particularly strong in the inner part of spiral
galaxies, also explains why we find that holes outside R25 are larger and
older. We derive the scale height of the HI disk as a function of
galactocentric radius and find that the disk flares up in all galaxies. We
proceed to derive the surface and volume porosity (Q2D and Q3D) and find that
this correlates with the type of the host galaxy: later Hubble types tend to be
more porous. The size distribution of the holes in our sample follows a power
law with a slope of a ~ -2.9. Assuming that the holes are the result of massive
star formation, we derive values for the supernova rate (SNR) and star
formation rate (SFR) which scales with the SFR derived based on other tracers.
If we extrapolate the observed number of holes to include those that fall below
our resolution limit, down to holes created by a single supernova, we find that
our results are compatible with the hypothesis that HI holes result from star
formation.Comment: 142 pages, 55 figures, accepted for publication in the Astronomical
Journa
Feeding Strategies of Optaflexx on Growth Performance and Carcass Characteristics of Feedlot Steers
Live BW and carcass traits of steer calves were evaluated after feeding Optaflexx (200mg/day) for 35 days on an intermittent basis or continuously. The negative control consisted of 63 days on the same diet without Optaflexx, whereas the positive control consisted of Optaflexx supplemented daily during the last 35 days prior to harvest. The four-day intermittent treatment consisted of feeding Optaflexx for seven days, followed by four days of no Optaflexx, while the seven-day intermittent treatment consisted of seven days on Optaflexx, followed by seven days off. In both the four-day and seven-day intermittent treatments, cattle received Optaflexx for a total of 35 days. Regardless of the delivery pattern, feeding Optaflexx increased ADG, DMI, and live BW. Feeding 200 mg per steer daily of Optaflexx for a total of 35 days in either four-day or seven-day intermittent patterns was as effective but no more so as continuous feeding for a 35-day period
Feeding Strategies of Optaflexx on Growth Performance and Carcass Characteristics of Feedlot Steers
Live BW and carcass traits of steer calves were evaluated after feeding Optaflexx (200mg/day) for 35 days on an intermittent basis or continuously. The negative control consisted of 63 days on the same diet without Optaflexx, whereas the positive control consisted of Optaflexx supplemented daily during the last 35 days prior to harvest. The four-day intermittent treatment consisted of feeding Optaflexx for seven days, followed by four days of no Optaflexx, while the seven-day intermittent treatment consisted of seven days on Optaflexx, followed by seven days off. In both the four-day and seven-day intermittent treatments, cattle received Optaflexx for a total of 35 days. Regardless of the delivery pattern, feeding Optaflexx increased ADG, DMI, and live BW. Feeding 200 mg per steer daily of Optaflexx for a total of 35 days in either four-day or seven-day intermittent patterns was as effective but no more so as continuous feeding for a 35-day period
Paradoxical expression of INK4c in proliferative multiple myeloma tumors: bi-allelic deletion vs increased expression
BACKGROUND: A high proliferative capacity of tumor cells usually is associated with shortened patient survival. Disruption of the RB pathway, which is critically involved in regulating the G1 to S cell cycle transition, is a frequent target of oncogenic events that are thought to contribute to increased proliferation during tumor progression. Previously, we determined that p18INK4c, an essential gene for normal plasma cell differentiation, was bi-allelically deleted in five of sixteen multiple myeloma (MM) cell lines. The present study was undertaken to investigate a possible role of p18INK4c in increased proliferation of myeloma tumors as they progress. RESULTS: Thirteen of 40 (33%) human myeloma cell lines do not express normal p18INK4c, with bi-allelic deletion of p18 in twelve, and expression of a mutated p18 fragment in one. Bi-allelic deletion of p18, which appears to be a late progression event, has a prevalence of about 2% in 261 multiple myeloma (MM) tumors, but the prevalence is 6 to10% in the 50 tumors with a high expression-based proliferation index. Paradoxically, 24 of 40 (60%) MM cell lines, and 30 of 50 (60%) MM tumors with a high proliferation index express an increased level of p18 RNA compared to normal bone marrow plasma cells, whereas this occurs in only five of the 151 (3%) MM tumors with a low proliferation index. Tumor progression is often accompanied by increased p18 expression and an increased proliferation index. Retroviral-mediated expression of exogenous p18 results in marked growth inhibition in three MM cell lines that express little or no endogenous p18, but has no effect in another MM cell line that already expresses a high level of p18. CONCLUSION: Paradoxically, although loss of p18 appears to contribute to increased proliferation of nearly 10% of MM tumors, most MM cell lines and proliferative MM tumors have increased expression of p18. Apart from a small fraction of cell lines and tumors that have inactivated the RB1 protein, it is not yet clear how other MM cell lines and tumors have become insensitive to the anti-proliferative effects of increased p18 expression
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