The binding of double-stranded (ds) DNA to mica can be controlled through ion-exchanging the mica with divalent cations. Measurements of the end-to-end distance of linear DNA molecules discriminate ...whether the binding mechanism occurs through 2D surface equilibration or kinetic trapping. A range of linear dsDNA fragments have been used to investigate length dependences of binding. Mica, ion-exchanged with Ni(II) usually gives rise to kinetically trapped DNA molecules, however, short linear fragments (<800 bp) are seen to deviate from the expected behaviour. This indicates that ion-exchanged mica is heterogeneous, and contains patches or domains, separating different ionic species. These results correlate with imaging of dsDNA under aqueous buffer on Ni(II)-mica and indicate that binding domains are of the order of 100 nm in diameter. Shorter DNA fragments behave intermediate to the two extreme cases of 2D equilibration and kinetic trapping. Increasing the incubation time of Ni(II) on mica, from minutes to hours, brings the conformations of the shorter DNA fragments closer to the theoretical value for kinetic trapping, indicating that long timescale kinetics play a role in ion-exchange. X-ray photoelectron spectroscopy (XPS) was used to confirm that the relative abundance of Ni(II) ions on the mica surface increases with time. These findings can be used to enhance spatial control of binding of DNA to inorganic surfaces with a view to patterning high densities arrays.
This study is an investigation of the stellar density profile of the Galactic disc in the anticentre direction. We select over 40 000 early A stars from INT/WFC Photometric Hα Survey of the Northern ...Galactic Plane (IPHAS) photometry in the Galactic longitude range 160° < l < 200° close to the equatorial plane (−1° < b < +1°). We then compare their observed reddening-corrected apparent magnitude distribution with simulated photometry obtained from parametrized models in order to set constraints on the anticentre stellar density profile. By selecting A stars, we are appraising the properties of a population only ∼100 Myr old. We find that the stellar density profile of young stars is well fit to an exponential with length-scale of (3020 ± 120statistical± 180systematic) pc, which is comparable to that obtained in earlier studies, out to a Galactocentric radius of RT= (13.0 ± 0.5statistical± 0.6systematic) kpc. At larger radii, the rate of decline appears to increase with the scalelength dropping to (1200 ± 300statistical± 70systematic) pc. This result amounts to a refinement of the conclusions reached in previous studies that the stellar density profile is abruptly truncated. The IPHAS A star data are not compatible with models that propose a sudden change in metallicity at RG= 10 kpc.
The Isaac Newton Telescope (INT) Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is a 1800-deg2 CCD survey of the northern Milky Way spanning the latitude range −5° < b < + 5° and ...reaching down to r′≃ 20 (10s). Representative observations and an assessment of point-source data from IPHAS, now underway, are presented. The data obtained are Wide Field Camera images in the Hα narrow-band, and Sloan r′ and i′ broad-band filters. We simulate IPHAS (r′−Hα, r′−i′) point-source colours using a spectrophotometric library of stellar spectra and available filter transmission profiles: this defines the expected colour properties of (i) solar metallicity stars, without Hα emission, and (ii) emission-line stars. Comparisons with observations of fields in Aquila show that the simulations of normal star colours reproduce the observations well for all spectral types earlier than M. A further comparison between colours synthesized from long-slit flux-calibrated spectra and IPHAS photometry for six objects in a Taurus field confirms the reliability of the pipeline calibration. Spectroscopic follow-up of a field in Cepheus shows that sources lying above the main stellar locus in the (r′− Hα, r′−i′) plane are confirmed to be emission-line objects with very few failures. In this same field, examples of Hα deficit objects (a white dwarf and a carbon star) are shown to be readily distinguished by their IPHAS colours. The role IPHAS can play in studies of spatially resolved northern Galactic nebulae is discussed briefly and illustrated by a continuum-subtracted mosaic image of Shajn 147 (a supernova remnant, 3° in diameter). The final catalogue of IPHAS point sources will contain photometry on about 80 million objects. Used on its own, or in combination with near-infrared photometric catalogues, IPHAS is a major resource for the study of stellar populations making up the disc of the Milky Way. The eventual yield of new northern emission-line objects from IPHAS is likely to be an order of magnitude increase on the number already known.
We present u-, g-, r-, i- and z-band optical images and associated catalogues taken primarily with the Isaac Newton Telescope Wide Field Camera on the European Large Area ISO Survey (ELAIS) N1 and ...N2, First Look Survey and Lockman Hole fields comprising a total of 1000 h of integration time over 80 deg2 and approximately 4.3 million objects. In this paper we outline the observations and data processing and characterize the completeness, reliability, photometric and astrometric accuracy of this data set. All images have been photometrically calibrated using the Sloan Digital Sky Survey and a uniform and homogeneous data set is composed over all the observed fields. Magnitude limits are u, g, r, i, z of 23.9, 24.5, 24.0, 23.3, 22.0 (AB, 5σ). These data have been used for optical identification of past and ongoing projects including the surveys ELAIS, Spitzer Wide-Area Infrared Extragalactic Survey, Spitzer Extragalactic Representative Volume Survey and Herschel Multi-tiered Extragalactic Survey.
Gaia Data Release 2 Evans, D. W.; Riello, M.; De Angeli, F. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Aims.
We describe the photometric content of the second data release of the
Gaia
project (
Gaia
DR2) and its validation along with the quality of the data.
Methods.
The validation was mainly carried ...out using an internal analysis of the photometry. External comparisons were also made, but were limited by the precision and systematics that may be present in the external catalogues used.
Results.
In addition to the photometric quality assessment, we present the best estimates of the three photometric passbands. Various colour-colour transformations are also derived to enable the users to convert between the
Gaia
and commonly used passbands.
Conclusions.
The internal analysis of the data shows that the photometric calibrations can reach a precision as low as 2 mmag on individual CCD measurements. Other tests show that systematic effects are present in the data at the 10 mmag level.
Gaia Early Data Release 3 Riello, M.; De Angeli, F.; Evans, D. W. ...
Astronomy and astrophysics (Berlin),
05/2021, Letnik:
649
Journal Article
Recenzirano
Context. Gaia
Early Data Release 3 (
Gaia
EDR3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency
Gaia
satellite ...during the first 34 months of its operational phase.
Aims.
In this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the
Gaia
EDR3 catalogue.
Methods.
The processing broadly followed the same procedure as for
Gaia
DR2, but with significant improvements in several aspects of the blue and red photometer (BP and RP) preprocessing and in the photometric calibration process. In particular, the treatment of the BP and RP background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. The photometric calibration models have also been updated to account for flux loss over the whole magnitude range. Significant improvements in the modelling and calibration of the
Gaia
point and line spread functions have also helped to reduce a number of instrumental effects that were still present in DR2.
Results. Gaia
EDR3 contains 1.806 billion sources with
G
-band photometry and 1.540 billion sources with
G
BP
and
G
RP
photometry. The median uncertainty in the
G
-band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2 mmag at magnitude
G
= 10–14, 0.8 mmag at
G
≈ 17, and 2.6 mmag at
G
≈ 19. The significant magnitude term found in the
Gaia
DR2 photometry is no longer visible, and overall there are no trends larger than 1 mmag mag
−1
. Using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. A detailed description of the residual systematic effects is provided. Overall the quality of the calibrated mean photometry in
Gaia
EDR3 is superior with respect to DR2 for all bands.
A tumour of vascular origin in a horse Wise, J. C.; Crosby, D. E.; Walton, A. N. ...
Equine veterinary education,
October 2021, Letnik:
33, Številka:
10
Journal Article
Recenzirano
Summary
Tumours of vascular origin are uncommon in horses. This report describes the surgical treatment of a large subcutaneous tumour in a Quarter Horse colt. The histopathological appearance of the ...mass was most consistent with a haemangioma. While these neoplasms of vascular origin are often difficult to characterise, it has been suggested that there is a continuum of types with some cases falling between the categories. Further classification of vascular tumours requires special stains and immunohistochemical techniques.
We present contemporary optical and infrared spectroscopic observations of the type IIn SN 1998S covering the period between 3 and 127 days after discovery. During the first week the spectra are ...characterized by prominent broad H, He and C iii/N iii emission lines with narrow peaks, superimposed on a very blue continuum (T∼24 000 K). In the following two weeks the C iii/N iii emission vanished, together with the broad emission components of the H and He lines. Broad, blueshifted absorption components appeared in the spectra. The temperature of the continuum also dropped to ∼14 000 K. By the end of the first month the spectrum comprised broad, blueshifted absorptions in H, He, Si ii, Fe ii and Sc ii. By day 44, broad emission components in H and He reappeared in the spectra. These persisted to as late as days ∼100–130, becoming increasingly asymmetric. We agree with Leonard et al. that the broad emission lines indicate interaction between the ejecta and circumstellar material (CSM) emitted by the progenitor. We also agree that the progenitor of SN 1998S appears to have gone through at least two phases of mass-loss, giving rise to two CSM zones. Examination of the spectra indicates that the inner zone extended to ≤90 au, while the outer CSM extended from 185 au to over 1800 au. We also present high-resolution spectra obtained at days 17 and 36. These spectra exhibit narrow P Cygni H i and He i lines superimposed on shallower, broader absorption components. Narrow lines of N ii, O iii, Ne iii and Fe iii are also seen. We attribute the narrow lines to recombination and heating following ionization of the outer CSM shell by the UV/X-ray flash at shock breakout. Using these lines, we show that the outer CSM had a velocity of 40–50 km s−1. Assuming a constant velocity, we can infer that the outer CSM wind commenced more than 170 years ago, and ceased about 20 years ago, while the inner CSM wind may have commenced less than 9 years ago. During the era of the outer CSM wind the outflow from the progenitor was high — at least ∼2×10−5 M⊙ yr−1. This corresponds to a mass-loss of at least ∼0.003 M⊙, suggesting a massive progenitor. The shallower, broader absorption is of width ∼350 km s−1, and may have arisen from a component of the outer CSM shell produced when the progenitor was going through a later blue supergiant phase. Alternatively, it may have been produced by the acceleration of the outer CSM by the radiation pressure of the UV precursor. We also describe and model first-overtone emission in carbon monoxide observed in SN 1998S. We deduce a CO mass of ∼10−3 M⊙ moving at ∼2200 km s−1, and infer a mixed metal/He core of about 4 M⊙, again indicating a massive progenitor. Only three core-collapse supernovae have been observed in the K band at post-100 days, and all three have exhibited emission from CO.
The Muon g − 2 Experiment at Fermi National Accelerator Laboratory (FNAL) has measured the muon anomalous precession frequency ωam to an uncertainty of 434 parts per billion (ppb), statistical, and ...56 ppb, systematic, with data collected in four storage ring configurations during its first physics run in 2018. When combined with a precision measurement of the magnetic field of the experiment's muon storage ring, the precession frequency measurement determines a muon magnetic anomaly of aμ ( FNAL ) = 116 592 040 ( 54 ) × 10−11 (0.46 ppm). This article describes the multiple techniques employed in the reconstruction, analysis, and fitting of the data to measure the precession frequency. It also presents the averaging of the results from the 11 separate determinations of ωam, and the systematic uncertainties on the result.
Abstract
We present an abundance analysis of a sample of Galactic bulge planetary nebulae (GBPNe). The observational data set consists of spectra of 88 nebulae obtained with the FLAIR II multiobject ...spectrograph on the UK Schmidt Telescope, together with spectra of 42 nebulae obtained with the RGO Spectrograph on the Anglo-Australian Telescope. After selecting those for which reliable nebular electron temperatures could be derived, collisionally excited line abundances were derived for 45 GBPNe.
These were then compared with similarly derived abundances for 54 Galactic disc PNe (GDPNe), taken from the work of Kingsburgh & Barlow. We find that within the errors the abundances have the same average values, essentially the same distributions - including that for the mass-sensitive N/O ratio - and show the same relationships. The width of the nitrogen distribution exceeds that arising from errors, which could be a consequence of the range of precursor masses. The ratio of Type-I to non-Type-I PNe in the bulge and disc samples is similar, 18 and 25 per cent respectively. For the GDPNe, we find larger N/H and N/O ratios for the small number of those with He/H > 0.14, compared with those with He/H < 0.14.
For neither disc nor bulge sample is there any strong evidence for a depletion of oxygen for the higher-mass precursor stars (Type I PNe). We find no correlation between O/H and N/O or He/H. On the N/O to He/H plane, the bulge and disc PNe show a distribution whereby the low N/O values only occur for low He/H values, but at N/O > 0.25 the whole range of He/H values were sampled. The theoretical tracks to which we compare our data do not explain the PNe with low He/H abundance and high N/O ratio.
Realistic uncertainties in collisionally excited lines (CEL) abundances for individual PNe are quite large, of the order of 40 per cent for oxygen. Large samples are therefore required to get good statistical accuracy. This is usually achieved by combining many studies, and so we have compared the results of a number of published studies with our own, to search for any systematic differences. The average abundances are found to be the same within the errors except for cases where the abundance derivation methods are dissimilar, where systematic differences can occur. The N/O ratio is especially sensitive to the details of the abundance derivations.
Our bulge PN sample shows no evidence for either very-low-metallicity objects or for super-metal-rich objects - the implied mass and age distributions of the bulge PN precursor stars are indistinguishable within the observational errors from those in the local Galactic disc.
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