Astronomical wide-field imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new ...wide-field interferometric imager that uses the w-stacking algorithm and can make use of the w-snapshot algorithm. The performance dependences of casa's w-projection and our new imager are analysed and analytical functions are derived that describe the required computing cost for both imagers. On data from the Murchison Widefield Array, we find our new method to be an order of magnitude faster than w-projection, as well as being capable of full-sky imaging at full resolution and with correct polarization correction. We predict the computing costs for several other arrays and estimate that our imager is a factor of 2–12 faster, depending on the array configuration. We estimate the computing cost for imaging the low-frequency Square Kilometre Array observations to be 60 PetaFLOPS with current techniques. We find that combining w-stacking with the w-snapshot algorithm does not significantly improve computing requirements over pure w-stacking. The source code of our new imager is publicly released.
The GLIMPSE (Galactic Legacy Mid-Plane Survey Extraordinaire) Point Source Catalog of 630 million mid-infrared sources toward the inner Galaxy, 10 , "l" 65 , 65 and "b" , 1, was used to determine the ...distribution of stars in Galactic longitude, l, latitude, b, and apparent magnitude, m. The counts versus longitude can be approximated by the modified Bessel function N = N sub(0)(l/l sub(0)) K sub(1)(l/l sub(0)), where l sub(0) is insensitive to limiting magnitude, band choice, and side of Galactic center: l sub(0) = 17-30 with a best-fit value in the 4.5 km band of l sub(0) = 24 c 4. Modeling the source distribution as an exponential disk yields a radial scale length of H sub(*) = 3.9 c 0.6 kpc. There is a pronounced north-south asymmetry in source counts for "l" 30, with 625% more stars in the north. For l = 10-30, there is a strong enhancement of stars of m = 11.5-13.5 mag. A linear bar passing through the Galactic center with half-length R sub(bar) = 4.4 c 0.5 kpc, tilted by h = 44 c 10 to the Sun-Galactic center line, provides the simplest interpretation of these data. We examine the possibility that enhanced source counts at l = 26-28, 31.5-34, and 306-309 are related to Galactic spiral structure. Total source counts are depressed in regions where the counts of red objects (m sub(K)-m sub(8.0) > 3) peak. In these areas, the counts are reduced by extinction due to molecular gas, high diffuse backgrounds associated with star formation, or both.
Summary
The skin commensal and opportunistic pathogen Staphylococcus epidermidis is the leading cause of nosocomial and biofilm‐associated infections. Little is known about the mechanisms by which S. ...epidermidis protects itself against the innate human immune system during colonization and infection. We used scanning electron microscopy to demonstrate that the exopolysaccharide intercellular adhesin (PIA) resides in fibrous strands on the bacterial cell surface, and that lack of PIA production results in complete loss of the extracellular matrix material that has been suggested to mediate immune evasion. Phagocytosis and killing by human polymorphonuclear leucocytes was significantly increased in a mutant strain lacking PIA production compared with the wild‐type strain. The mutant strain was also significantly more susceptible to killing by major antibacterial peptides of human skin, cationic human β‐defensin 3 and LL‐37, and anionic dermcidin. PIA represents the first defined factor of the staphylococcal biofilm matrix that protects against major components of human innate host defence.
The Bubbling Galactic Disk Churchwell, E; Povich, M. S; Allen, D ...
The Astrophysical journal,
10/2006, Letnik:
649, Številka:
2
Journal Article
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A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully ...enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H II regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H II regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H II regions. Some of the bubbles may be the outer edges of H II regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1' and 3' with over 98% having angular diameters less than 10' and 88% less than 4'. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.
We determine and tabulate A sub( lambda )/A sub(K), the wavelength dependence of interstellar extinction, in the Galactic plane for 1.25 mu m less than or equal to lambda less than or equal to mu 8.0 ...mu m along two lines of sight: l = 42 degree and 284 degree . The first is a relatively quiescent and unremarkable region; the second contains the giant H II region RCW 49, as well as a "field" region unrelated to the cluster and nebulosity. Areas near these Galactic longitudes were imaged at J, H, and K bands by 2MASS and at 3-8 mu m by Spitzer for the GLIMPSE Legacy program. We measure the mean values of the color excess ratios (A sub( lambda ) - A sub(K))/(A sub(J) - A sub(K)) directly from the color distributions of observed stars. The extinction ratio between two of the filters, e.g., A sub(J)/A sub(K), is required to calculate A sub( lambda )/A sub(K) from those measured ratios. We use the apparent JHK magnitudes of giant stars along our two sight lines and fit the reddening as a function of magnitude (distance) to determine A sub(J)kpc super(-1), A sub(K)kpc super(-1), and A sub(J)/A sub(K). Our values of A sub( lambda )/A sub(K) show a flattening across the 3-8 mu m wavelength range, roughly consistent with the extinction measurements derived by Lutz and coworkers for the sight line toward the Galactic center.
The effect of second-generation pneumococcal conjugate vaccines on invasive pneumococcal disease (IPD) strain distributions have not yet been well described. We analysed IPD isolates recovered from ...children aged <5 years through Active Bacterial Core surveillance before (2008–2009; n = 828) and after (2011–2013; n = 600) 13-valent pneumococcal conjugate vaccine (PCV13) implementation. We employed conventional testing, PCR/electrospray ionization mass spectrometry and whole genome sequence (WGS) analysis to identify serotypes, resistance features, genotypes, and pilus types. PCV13, licensed in February 2010, effectively targeted all major 19A and 7F genotypes, and decreased antimicrobial resistance, primarily owing to removal of the 19A/ST320 complex. The strain complex contributing most to the remaining β-lactam resistance during 2011–2013 was 35B/ST558. Significant emergence of non-vaccine clonal complexes was not evident. Because of the removal of vaccine serotype strains, positivity for one or both pilus types (PI-1 and PI-2) decreased in the post-PCV13 years 2011–2013 relative to 2008–2009 (decreases of 32–55% for PI-1, and >95% for PI-2 and combined PI-1 + PI-2). β-Lactam susceptibility phenotypes correlated consistently with transpeptidase region sequence combinations of the three major penicillin-binding proteins (PBPs) determined through WGS analysis. Other major resistance features were predictable by DNA signatures from WGS analysis. Multilocus sequence data combined with PBP combinations identified progeny, serotype donors and recipient strains in serotype switch events. PCV13 decreased the frequency of all PCV13 serotype clones and concurrently decreased the frequency of strain subsets with resistance and/or adherence features conducive to successful carriage. Our results serve as a reference describing key features of current paediatric IPD strains in the USA after PCV13 implementation.
Theropod dinosaurs are well known for having a ziphodont dentition: serrated, blade-shaped teeth that they used for cutting through prey. Serrations along the carinae of theropod teeth are composed ...of true denticles, a complex arrangement of dentine, enamel, and interdental folds. This structure would have supported individual denticles and dissipated the stresses associated with feeding. These particular serrations were previously thought to be unique to theropod dinosaurs and some other archosaurs. Here, we identify the same denticles and interdental folds forming the cutting edges in the teeth of a Permian gorgonopsian synapsid, extending the temporal and phylogenetic distribution of this dental morphology. This remarkable instance of convergence not only represents the earliest record of this adaptation to hypercarnivory but also demonstrates that the first iteration of this feature appeared in non-mammalian synapsids. Comparisons of tooth serrations in gorgonopsians with those of earlier synapsids and hypercarnivorous mammals reveal some gorgonopsians acquired a complex tissue arrangement that differed from other synapsids.
We report 269 mid-infrared bubbles within 10' of the Galactic center from visual inspection of the Spitzer GLIMPSE II Legacy Science program images. The surface density of bubbles is 65 deg(-2) or ...about 3 times that detected in longitudes l = 10'-65', because the inner 10' of longitude were more thoroughly searched for small bubbles. There is a gradient in the number of bubbles with longitude with an increase of about a factor of 2 from 2' to 10'; this is probably the result of several factors, including decreasing diffuse background brightness, confusion, and opacity with longitude. Bubble eccentricities are typically between 0.6 and 0.8, and > 50% show evidence for blowouts, which we suggest result from local density fluctuations of the ISM and/or anisotropic stellar winds and radiation fields. The fraction of bubbles identified with H II regions and clusters is only about half that found at l > 10'. This is largely a result of the much smaller angular diameter of bubbles cataloged in the inner Galaxy than in the outer Galaxy. At least 12% of the bubbles have morphologies suggestive of triggered star formation. Most of the bubbles that show evidence for triggered star formation in the inner Galaxy have not formed secondary bubbles; it is postulated that this may be because they are too young to have had time for this to occur.
ABSTRACT The Murchison Widefield Array (MWA) has collected hundreds of hours of Epoch of Reionization (EoR) data and now faces the challenge of overcoming foreground and systematic contamination to ...reduce the data to a cosmological measurement. We introduce several novel analysis techniques, such as cable reflection calibration, hyper-resolution gridding kernels, diffuse foreground model subtraction, and quality control methods. Each change to the analysis pipeline is tested against a two-dimensional power spectrum figure of merit to demonstrate improvement. We incorporate the new techniques into a deep integration of 32 hours of MWA data. This data set is used to place a systematic-limited upper limit on the cosmological power spectrum of mK2 at k = 0.27 h Mpc−1 and z = 7.1, consistent with other published limits, and a modest improvement (factor of 1.4) over previous MWA results. From this deep analysis, we have identified a list of improvements to be made to our EoR data analysis strategies. These improvements will be implemented in the future and detailed in upcoming publications.
Human polymorphonuclear leukocytes (PMNs or neutrophils) are essential to the innate immune response against bacterial pathogens. Recent evidence suggests that PMN apoptosis facilitates resolution of ...inflammation during bacterial infection. Although progress has been made toward understanding apoptosis in neutrophils, very little is known about transcriptional regulation of this process during bacterial infection. To gain insight into the molecular processes that facilitate resolution of infection, we measured global changes in PMN gene expression during phagocytosis of a diverse group of bacterial pathogens. Genes encoding key effectors of apoptosis were up-regulated, and receptors critical to innate immune function were down-regulated during apoptosis induced by phagocytosis of Burkholderia cepacia, Borrelia hermsii, Listeria monocytogenes, Staphylococcus aureus, and Streptococcus pyogenes. Importantly, we identified genes that comprise a common apoptosis differentiation program in human PMNs after phagocytosis of pathogenic bacteria. Unexpectedly, phagocytosis of Str. pyogenes induced changes in neutrophil gene expression not observed with other pathogens tested, including down-regulation of 21 genes involved in responses to IFN. Compared with other bacteria, PMN apoptosis was significantly accelerated by Str. pyogenes and was followed by necrosis. Thus, we hypothesize that there are two fundamental outcomes for the interaction of bacterial pathogens with neutrophils: (i) phagocytosis of bacteria induces an apoptosis differentiation program in human PMNs that contributes to resolution of bacterial infection, or (ii) phagocytosis of microorganisms such as Str. pyogenes alters the apoptosis differentiation program in neutrophils, resulting in pathogen survival and disease.
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