356 research outputs found
A Quantitative Non-radial Oscillation Model for the Subpulses in PSR B0943+10
In this paper, we analyze time series measurements of PSR B0943+10 and fit
them with a non-radial oscillation model. The model we apply was first
developed for total intensity measurements in an earlier paper, and expanded to
encompass linear polarization in a companion paper to this one. We use PSR
B0943+10 for the initial tests of our model because it has a simple geometry,
it has been exhaustively studied in the literature, and its behavior is
well-documented. As prelude to quantitative fitting, we have reanalyzed
previously published archival data of PSR B0943+10 and uncovered subtle but
significant behavior that is difficult to explain in the framework of the
drifting spark model. Our fits of a non-radial oscillation model are able to
successfully reproduce the observed behavior in this pulsar.Comment: 45 pages, 16 figures, accepted Ap
A Commentary
17 USC 105 interim-entered record; under review.It is with great interest that we read the article on the twentyfirst-century hospital ship by the esteemed Rear Adm. (ret.) Michael Baker, Mr. Jacob Baker, and Capt. (ret.) Fred âSkipâ Burkle. Many of the concepts they outline are viable options worth consideration, but the future hospital ship is only one piece of the system-based, integrated approach for projecting medical power in support of Naval superiority.Identified in text as U.S. Government work
A Phase 3 Study of Evolocumab (AMG 145) in Statin-Treated Japanese Patients at High Cardiovascular Risk
Evolocumab (AMG 145), a fully human monoclonal antibody against PCSK9, significantly reduced low-density lipoprotein cholesterol (LDL-C) levels in phase 2 and 3 studies. This phase 3 study evaluated the efficacy and safety of evolocumab plus atorvastatin in Japanese patients with hyperlipidemia or mixed dyslipidemia and high cardiovascular risk. Patients were randomized to atorvastatin 5 or 20Â mg/day for 4Â weeks. Subsequently, patients underwent second randomization to evolocumab 140Â mg biweekly (Q2W) or 420Â mg monthly (QM) or placebo Q2W or QM. Coprimary end points were % change from baseline in LDL-C at week 12 and mean of weeks 10 and 12. Secondary end points included change and % change in other lipids and proportion of patients reaching LDL-C <70Â mg/dl. Adverse events and laboratory values were recorded. Four hundred four patients were randomized to study drug. At baseline, the mean (SD) age was 61 (10) years (placebo) and 62 (11) years (evolocumab); 39% and 40% were women; 14% and 12% had cerebrovascular or peripheral arterial disease; and 51% and 47% had diabetes. At entry, mean (SD) calculated LDL-C was 128 (23) mg/dL; after stabilization on atorvastatin 5 and 20Â mg/day, baseline LDL-C levels were 118 (35) and 94 (24) mg/dL, respectively. Mean LDL-C reductions at week 12 for evolocumab versus placebo ranged from 67% to 76%. No imbalances were observed in adverse events between treatment groups. Efficacy and safety for Q2W or QM evolocumab dosing were similar. In conclusion, in high-risk Japanese patients receiving stable statin therapy, evolocumab markedly reduced LDL-C and was well tolerated
Ultrasound-triggered antibiotic release from PEEK clips to prevent spinal fusion infection: Initial evaluations.
Despite aggressive peri-operative antibiotic treatments, up to 10% of patients undergoing instrumented spinal surgery develop an infection. Like most implant-associated infections, spinal infections persist through colonization and biofilm formation on spinal instrumentation, which can include metal screws and rods for fixation and an intervertebral cage commonly comprised of polyether ether ketone (PEEK). We have designed a PEEK antibiotic reservoir that would clip to the metal fixation rod and that would achieve slow antibiotic release over several days, followed by a bolus release of antibiotics triggered by ultrasound (US) rupture of a reservoir membrane. We have found using human physiological fluid (synovial fluid), that higher levels (100â500 ÎŒg) of vancomycin are required to achieve a marked reduction in adherent bacteria vs. that seen in the common bacterial medium, trypticase soy broth. To achieve these levels of release, we applied a polylactic acid coating to a porous PEEK puck, which exhibited both slow and US-triggered release. This design was further refined to a one-hole or two-hole cylindrical PEEK reservoir that can clip onto a spinal rod for clinical use. Short-term release of high levels of antibiotic (340 ± 168 ÎŒg), followed by US-triggered release was measured (7420 ± 2992 ÎŒg at 48 h). These levels are sufficient to prevent adhesion of Staphylococcus aureus to implant materials. This study demonstrates the feasibility of an US-mediated antibiotic delivery device, which could be a potent weapon against spinal surgical site infection. Statement of Significance: Spinal surgical sites are prone to bacterial colonization, due to presence of instrumentation, long surgical times, and the surgical creation of a dead space (â„5 cm 3 ) that is filled with wound exudate. Accordingly, it is critical that new approaches are developed to prevent bacterial colonization of spinal implants, especially as neither bulk release systems nor controlled release systems are available for the spine. This new device uses non-invasive ultrasound (US) to trigger bulk release of supra-therapeutic doses of antibiotics from materials commonly used in existing surgical implants. Thus, our new delivery system satisfies this critical need to eradicate surviving bacteria, prevent resistance, and markedly lower spinal infection rates
Massive Star Formation in the Molecular Ring Orbiting the Black Hole at the Galactic Center
A ring of dense molecular gas extending 2-7 pc orbits the supermassive black
hole Sgr A* at the center of our Galaxy. Using the Green Bank Telescope, we
detected water maser lines and both narrow (0.35 km/s) and broad (30 - 50 km/s)
methanol emission from the molecular ring. Two of the strongest methanol lines
at 44 GHz are confirmed as masers by interferometric observations. These class
I methanol masers are collisionally excited and are signatures of early phases
of massive star formation in the disk of the Galaxy, suggesting that star
formation in the molecular ring is in its early phase. Close inspection of the
kinematics of the associated molecular clumps in the HCN (J=1-0) line reveals
broad red-shifted wings indicative of disturbance by protostellar outflows from
young (few times 10^4 yr), massive stars embedded in the clumps. The thermal
methanol profile has a similar shape, with a narrow maser line superimposed on
a broad, red-shifted wing. Additional evidence for the presence of young
massive protostars is provided by shocked molecular hydrogen and a number of
striking ionized and molecular linear filaments in the vicinity of methanol
sources suggestive of 0.5-pc scale protostellar jets. Given that the
circumnuclear molecular ring is kinematically unsettled and thus is likely be
the result of a recent capture, the presence of both methanol emission and
broad, red-shifted HCN emission suggests that star formation in the
circumnuclear ring is in its infancy.Comment: 13 pages, 4 figures, ApJ Letters (in press
A Pulsational Model for the Orthogonal Polarization Modes in Radio Pulsars
In an earlier paper, we introduced a model for pulsars in which non-radial
oscillations of high spherical degree (\el) aligned to the magnetic axis of a
spinning neutron star were able to reproduce subpulses like those observed in
single-pulse measurements of pulsar intensity. The model did not address
polarization, which is an integral part of pulsar emission. Observations show
that many pulsars emit radio waves that appear to be the superposition of two
linearly polarized emission modes with orthogonal polarization angles. In this
paper, we extend our model to incorporate linear polarization. As before, we
propose that pulsational displacements of stellar material modulate the pulsar
emission, but now we apply this modulation to a linearly-polarized mode of
emission, as might be produced by curvature radiation. We further introduce a
second polarization mode, orthogonal to the first, that is modulated by
pulsational velocities. We combine these modes in superposition to model the
observed Stokes parameters in radio pulsars.Comment: 19 pages, 4 figures accepted Ap
Incorporating interactive 3-dimensional graphics in astronomy research papers
Most research data collections created or used by astronomers are
intrinsically multi-dimensional. In contrast, all visual representations of
data presented within research papers are exclusively 2-dimensional. We present
a resolution of this dichotomy that uses a novel technique for embedding
3-dimensional (3-d) visualisations of astronomy data sets in electronic-format
research papers. Our technique uses the latest Adobe Portable Document Format
extensions together with a new version of the S2PLOT programming library. The
3-d models can be easily rotated and explored by the reader and, in some cases,
modified. We demonstrate example applications of this technique including: 3-d
figures exhibiting subtle structure in redshift catalogues, colour-magnitude
diagrams and halo merger trees; 3-d isosurface and volume renderings of
cosmological simulations; and 3-d models of instructional diagrams and
instrument designs.Comment: 18 pages, 7 figures, submitted to New Astronomy. For paper with
3-dimensional embedded figures, see http://astronomy.swin.edu.au/s2plot/3dpd
Observations of Non-radial Pulsations in Radio Pulsars
We introduce a model for pulsars in which non-radial oscillations of high
spherical degree (l) aligned to the magnetic axis of a spinning neutron star
reproduce the morphological features of pulsar beams. In our model, rotation of
the pulsar carries a pattern of pulsation nodes underneath our sightline,
reproducing the longitude stationary structure seen in average pulse profiles,
while the associated time-like oscillations reproduce "drifting
subpulses"--features that change their longitude between successive pulsar
spins. We will show that the presence of nodal lines can account for observed
180 degree phase jumps in drifting subpulses and their otherwise poor phase
stability, even if the time-like oscillations are strictly periodic. Our model
can also account for the "mode changes" and "nulls" observed in some pulsars as
quasiperiodic changes between pulsation modes of different l or radial overtone
n, analogous to pulsation mode changes observed in oscillating white dwarf
stars. We will discuss other definitive and testable requirements of our model
and show that they are qualitatively supported by existing data. While
reserving judgment until the completion of quantitative tests, we are inspired
enough by the existing observational support for our model to speculate about
the excitation mechanism of the non-radial pulsations, the physics we can learn
from them, and their relationship to the period evolution of pulsars.Comment: 28 pages, 9 figures (as separate png files), Astrophysical Journal,
in pres
Genetically engineered E. coli Nissle attenuates hyperammonemia and prevents memory impairment in bileâduct ligated rats
Hyperammonemia associated with chronic liver disease (CLD) is implicated in the pathogenesis of hepatic encephalopathy (HE). The gut is a major source of ammonia production that contributes to hyperammonemia in CLD and HE and remains the primary therapeutic target for lowering hyperammonemia. As an ammoniaâlowering strategy, Escherichia coli Nissle 1917 bacterium was genetically modified to consume and convert ammonia to arginine (SâARG). SâARG was further modified to additionally synthesize butyrate (SâARG+BUT). Both strains were evaluated in bileâduct ligated (BDL) rats; experimental model of CLD and HE.
Methods
Oneâweek postâsurgery, BDLs received nonâmodified EcN (EcN), SâARG, SâARG+BUT (3x1011 CFU/day) or vehicle until sacrifice at 3â or 5âweeks. Plasma (ammonia/proâinflammatory/liverâfunction), liver fibrosis (hydroxyproline), liver mRNA (proâinflammatory/fibrogenic/antiâapoptotic) and colon mRNA (proâinflammatory) biomarkers were measured postâsacrifice. Memory, motorâcoordination, muscleâstrength, and locomotion were assessed at 5âweeks.
Results
In BDLâVeh rats, hyperammonemia developed at 3â and further increased at 5âweeks. This rise was prevented by SâARG and SâARG+BUT, whereas EcN was ineffective. Memory impairment was prevented only in SâARG+BUT vs BDLâVeh. Systemic inflammation (ILâ10/MCPâ1/endotoxin) increased at 3â and 5âweeks in BDLâVeh. SâARG+BUT attenuated inflammation at both timepoints (except 5âweek endotoxin) vs BDLâVeh, whereas SâARG only attenuated IPâ10 and MCPâ1 at 3âweeks. Circulating (ALT/AST/ALP/GGT/albumin/bilirubin) and gene expression liverâfunction markers (ILâ10/ILâ6/ILâ1ÎČ/TGFâÎČ/αâSMA/collagenâ1α1/Bclâ2) were not normalized by either strain. Colonic mRNA (TNFâα/ILâ1ÎČ/occludin) markers were attenuated by synthetic strains at both timepoints vs BDLâVeh.
Conclusion
SâARG and SâARG+BUT attenuated hyperammonemia, with SâARG+BUT additional memory protection likely due to greater antiâinflammatory effect. These innovative strategies, particularly SâARG+BUT, have potential to prevent HE
The Rosette Eye: the key transition phase in the birth of a massive star
Massive protostars dramatically influence their surroundings via
accretion-induced outflows and intense radiation fields. They evolve rapidly,
the disk and infalling envelope being evaporated and dissipated in
10 years. Consequently, they are very rare and investigating this important
phase of early stellar evolution is extremely difficult. Here we present the
discovery of a key transient phase in the emergence of a massive young star, in
which ultraviolet radiation from the new-born giant has just punctured through
its natal core. The massive young stellar object AFGL 961 II is readily
resolved in the near infrared. Its morphology closely resembles a cat's eye and
is here dubbed as the Rosette Eye. Emerging ionized flows blow out an hourglass
shaped nebula, which, along with the existence of strong near-infrared excess,
suggests the existence of an accretion disk in the perpendicular direction. The
lobes of the hourglass, however, are capped with arcs of static H
emission produced by fluorescence. This study has strong implications for our
understanding of how massive stars embark on their formation.Comment: 3 figure
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