1,859 research outputs found
Observations of the Structure and Dynamics of the Inner M87 Jet
M87 is the best source in which to study a jet at high resolution in
gravitational units because it has a very high mass black hole and is nearby.
The angular size of the black hole is second only to Sgr A*, which does not
have a strong jet. The jet structure is edge brightened with a wide opening
angle base and a weak counterjet. We have roughly annual observations for 17
years plus intensive monitoring at three week intervals for a year and five day
intervals for 2.5 months made with the Very Long Baseline Array (VLBA) at 43
GHz. The inner jet shows very complex dynamics, with apparent motions both
along and across the jet. Speeds from zero to over 2c are seen, with
acceleration observed over the first 3 milli-arcseconds. The counterjet
decreases in brightness much more rapidly than the main jet, as is expected
from relativistic beaming in an accelerating jet oriented near the
line-of-sight. Details of the structure and dynamics are discussed. The roughly
annual observations show side-to-side motion of the whole jet with a
characteristic time scale of about 9 years.Comment: 11 pages, 7 figures. Published in a special issue of Galaxies which
is the proceedings of "Blazars through Sharp Multi-Wavelength Eyes" edited by
J. L. Gomez, A. P. Marscher, and S. G. Jorsta
Blood immunoglobulins, complement and TNF receptor following minimally invasive surgery in patients undergoing pulmonary lobectomy
The reasons for improved survival following minimally invasive surgery remain elusive. Circulating mediators link surgical trauma, vascular and tissue homeostasis. Acute phase reactants, leukocytes and leukocyte Reactive Oxygen Species (ROS) are affected differentially by minimally invasive video-assisted thoracic surgery (VATS). Also, immunoglobulins, complement, TNF receptor and P-selectin changes have been observed, but the influence of minimally invasive surgery on these opsonins is less well defined. In this prospective randomised trial, 41 patients were randomly assigned to minimally invasive or open thoracic surgery, and immunoglobulins and vascular endothelial damage biomarkers were analysed. Humoral mediators (blood IgG, IgM, IgA; complement fragments C3, C4, and complement haemolytic index of activation CH50; TNF receptors I, II and P-selectin) were analysed before and 2, 5 and 7 days after surgery. Post-surgical changes in individual patients were determined. Substantial immunoglobulin decreases followed minimally invasive and open surgery. Decreased IgG, IgM and IgE were detected 2 days after surgery, and IgG and IgM after 7 days. These changes were greater than haemodilution, reaching greater significance in open surgery patients. Immunoglobulin decreases followed lymphocyte decreases. In contrast, increased complement and inflammatory endothelial cell signals (C3 and C4, soluble TNFR-II) were detected 7 days after surgery. In both groups, increased C3 and TNFR-II followed early acute phase reactants CRP, IL-6 and ROS. Acute phase reactants and CD4/CD8 lymphocytes were factors most attenuated in patients undergoing minimally invasive thoracic surgery (VATS). This study suggests local trauma mediators are better biomarkers than circulating opsonins in defining the response to minimally invasive surgery, and a systems approach, comparing individual metabolic responses, is effective in small patient groups
Interview with Lydia Groves
An interview with Lydia Groves regarding her experiences in a one-room school house.https://scholars.fhsu.edu/ors/1063/thumbnail.jp
Millimeter and Submillimeter Survey of the R Corona Australis Region
Using a combination of data from the Antarctic Submillimeter Telescope and
Remote Observatory (AST/RO), the Arizona Radio Observatory Kitt Peak 12m
telescope and the Arizona Radio Observatory 10m Heinrich Hertz Telescope, we
have studied the most active part of the R CrA molecular cloud in multiple
transitions of Carbon Monoxide, HCO and 870\micron continuum emission.
Since R CrA is nearby (130 pc), we are able to obtain physical spatial
resolution as high as 0.01pc over an area of 0.16 pc, with velocity
resolution finer than 1 km/s. Mass estimates of the protostar driving the
mm-wave emission derived from HCO, dust continuum emission and kinematic
techniques point to a young, deeply embedded protostar of 0.5-0.75
M, with a gaseous envelope of similar mass. A molecular outflow is
driven by this source that also contains at least 0.8 M of molecular
gas with 0.5 L of mechanical luminosity. HCO lines show the
kinematic signature of infall motions as well as bulk rotation. The source is
most likely a Class 0 protostellar object not yet visible at near-IR
wavelengths. With the combination of spatial and spectral resolution in our
data set, we are able to disentangle the effects of infall, rotation and
outflow towards this young object.Comment: 29 pages, 9 figures. Accepted for publication in the Astrophysical
Journa
Molecular Line Emission from Gravitationally Unstable Protoplanetary Disks
In the era of high resolution submillimeter interferometers, it will soon be
possible to observe the neutral circumstellar medium directly involved in gas
giant planet (GGP) formation at physical scales previously unattainable. In
order to explore possible signatures of gas giant planet formation via disk
instabilities, we have combined a 3D, non-local thermodynamic equilibrium (LTE)
radiative transfer code with a 3D, finite differences hydrodynamical code to
model molecular emission lines from the vicinity of a 1.4 M_J self-gravitating
proto-GGP. Here, we explore the properties of rotational transitions of the
commonly observed dense gas tracer, HCO+. Our main results are the following:
1. Very high lying HCO+ transitions (e.g. HCO+ J=7-6) can trace dense planet
forming clumps around circumstellar disks. Depending on the molecular
abundance, the proto-GGP may be directly imageable by the Atacama Large
Millimeter Array (ALMA). 2. HCO+ emission lines are heavily self-absorbed
through the proto-GGP's dense molecular core. This signature is nearly
ubiquitous, and only weakly dependent on assumed HCO+ abundances. The
self-absorption features are most pronounced at higher angular resolutions.
Dense clumps that are not self-gravitating only show minor self-absorption
features. 3. Line temperatures are highest through the proto-GGP at all assumed
abundances and inclination angles. Conversely, due to self-absorption in the
line, the velocity-integrated intensity may not be. High angular resolution
interferometers such as the Submillimeter Array (SMA) and ALMA may be able to
differentiate between competing theories of gas giant planet formation.Comment: 10 pages, 13 figures; Accepted by Ap
Dynamics of success and failure in phage and antibiotic therapy in experimental infections
BACKGROUND: In 1982 Smith and Huggins showed that bacteriophages could be at least as effective as antibiotics in preventing mortality from experimental infections with a capsulated E. coli (K1) in mice. Phages that required the K1 capsule for infection were more effective than phages that did not require this capsule, but the efficacies of phages and antibiotics in preventing mortality both declined with time between infection and treatment, becoming virtually ineffective within 16 hours. RESULTS: We develop quantitative microbiological procedures that (1) explore the in vivo processes responsible for the efficacy of phage and antibiotic treatment protocols in experimental infections (the Resistance Competition Assay, or RCA), and (2) survey the therapeutic potential of phages in vitro (the Phage Replication Assay or PRA). We illustrate the application and utility of these methods in a repetition of Smith and Huggins' experiments, using the E. coli K1 mouse thigh infection model, and applying treatments of phages or streptomycin. CONCLUSIONS: 1) The Smith and Huggins phage and antibiotic therapy results are quantitatively and qualitatively robust. (2) Our RCA values reflect the microbiological efficacies of the different phages and of streptomycin in preventing mortality, and reflect the decline in their efficacy with a delay in treatment. These results show specifically that bacteria become refractory to treatment over the term of infection. (3) The K1-specific and non-specific phages had similar replication rates on bacteria grown in broth (based on the PRA), but the K1-specific phage had markedly greater replication rates in mouse serum
High Frequency VLBI Imaging of the Jet Base of M87
VLBA and Global VLBI observations of M87 at 43 GHz, some new and some
previously published, are used to study the structural evolution of the jet
with a spatial resolution of under 100 Schwarzschild radii. The images, taken
between 1999 and 2004, have an angular resolution of 0.00043" x 0.00021". An
edge-brightened jet structure and an indication of a large opening angle at the
jet base are seen in all five epochs. In addition, a probable counter-jet is
seen in the latter three epochs. A 22 GHz VLBA image also confirms many of the
structures seen at the higher frequency, including the counter-jet. A
comparison of the counter-jet flux density at 22 and 43 GHz reveals that it is
not free-free absorbed at these frequencies.
Attempts to obtain speeds from the proper motions of jet and counter-jet
components indicate that these observations are undersampled. The closest pair
of images gives apparent speeds of 0.25 to 0.40c for the jet and 0.17c for the
counter-jet. These speeds should be treated as lower limits because of possible
errors in associating components between epochs. If they are real, they
indicate that the jet is oriented 30-45 degrees from the line-of-sight and that
the component speeds along the jet are 0.3-0.5c. Using the jet orientation
derived from proper motions, the spectral index of the the counter-jet, and a
jet-to-counter-jet brightness ratio of 14.4, the inferred bulk flow is
0.6-0.7c, which, given the considerable uncertainties in how to measure the
brightness ratio, is not significantly larger than the component speed.Comment: 16 pages, 1 table, 3 color figures, accepted to the Astrophysical
Journa
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