923 research outputs found
The Optical Polarization and Warm Absorber in IRAS 17020+4544
We report the detection of ionized absorption in the ASCA spectrum of the
narrow-line Seyfert 1 galaxy IRAS 17020+4544. Subsequent optical
spectropolarimetry revealed high polarization increasing from 3% in the red to
5% in the blue, indicating electron or dust scattering as a likely origin. The
broad emission line H is somewhat less polarized than the continuum,
supporting a location of the polarizing material within the AGN. The Balmer
line decrement and reddened optical spectrum support the presence of a dusty
warm absorber in this object.
We compared the broad band optical polarization and ionized X-ray absorption
of a collection of Seyfert 1 and 1.5 galaxies, excluding classes of objects
that are likely to have significant neutral X-ray absorption. Warm absorber
objects are generally more likely to have high optical polarization than
objects with no detected ionized absorption. This result lends additional
support to the idea that the warm absorber is associated with dust and implies
either that dust transmission is responsible for at least part of the
polarization or that the polarization is revealed because of the dimming of the
optical spectrum. Spectropolarimetry of Seyfert 1s generally locates the
scattering material inside the narrow-line region and often close to or within
the broad line region, consistent with estimates of the location of the dusty
warm absorber.Comment: 11 pages using (AASTeX) aaspp4.sty and 3 Postscript figures. Accepted
for publication in Astrophysical Journal Letter
The influence of Harmonia axyridis morbidity on 2-Isopropyl-3-methoxypyrazine in 'Cabernet Sauvignon' wine
Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae; the Multicolored Asian Lady Beetle; MALB) is a vineyard pest in many winemaking regions of the world due to its ability to taint juice and wine (âladybug taintâ) through excretion or extraction of 2-isopropyl-3-methoxypyrazine (IPMP) when the beetles are incorporated with the grapes at harvest. A common vineyard intervention is the use of insecticidal sprays and the resulting dead beetles are often incorporated in with the harvested fruit. The main objective of this study was to quantify the impact of dead MALB on IPMP concentrations in red wine. Duplicate 'Cabernet Sauvignon' wines were produced with the addition of 10 beetles·l-1 juice, added either live or at 1, 3, 7, or 60-days postmortem. A control wine with no added beetles was included. IPMP concentration was substantially higher in live-beetle wines, and decreased to base-line levels at approximately 6.5 days post-mortem. These results should assist in decisions on viticultural interventions, such as timing of insecticidal sprays, as well as the establishment of grape quality parameters.
Transnationalism and Social Work Education
Transnational movements, networks, and relationships are everywhere in this âworld on the moveâ (Williams & Graham, 2014, p. i1). Transnational peoples maintain relationships of interdependence and support with families and communities in their places of origin, often returning regularly, while starting new lives and making new connections. Transnationalism is characterized by mobilities and networks, by social integration, and by extended and extensive relationship ties of family, neighborhood, religious faith, or combinations thereof (Valtonen, 2008). While disciplines across the world including sociology, human geography, and cultural anthropology engage with the implications of transnationalism (Bauböck & Faist, 2010), social work in England and mainland Europe has not achieved similar levels of engagement. As Cox and Geisen state: âthe social world is being transformed by migration and social work is playing catch-upâ (2014, p. i162)
Targeting of anionic membrane species by lanthanide(III) complexes: towards improved MRI contrast agents for apoptosis
No abstract available
Direct measurement of the jet geometry in Seyfert galaxies
We demonstrate that, by combining optical, radio and X-ray observations of a
Seyfert, it is possible to provide a direct measurement of the angle
between the direction of the radio jet and the normal to the plane of the
spiral host galaxy. To do so, we make the assumptions that the inner radio jet
is perpendicular to the X-ray observed inner accretion disk, and that the
observed jet (or the stronger component, if the jet is two-sided) is physically
closer to Earth than the plane of the galaxy. We draw attention to the
possibility of measurement producing a result which is not self-consistent, in
which case for that galaxy, one of the assumptions must fail.Comment: 11 pages, 1 figure, accepted for publication in The Astrophysical
Journal Letter
Spectropolarimetry of the Luminous Narrow-Line Seyfert Galaxies IRAS 20181-2244 and IRAS 13224-3809
We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS
13324-3809 with a new spectropolarimeter on the RC spectrograph at the CTIO 4m
telescope. Previously it had been suggested that IRAS 20181-2244 was a Type 2
QSO and thus might contain an obscured broad-line region which could be
detected by the presence of broad Balmer lines in the polarized flux. We found
the object to be polarized at about 2%, and constant with wavelength, (unlike
most narrow-line Seyfert 1s), but with no evidence of broad Balmer lines in
polarized flux. The spectropolarimetry indicates that the scattering material
is inside the BLR. IRAS 13224-3809, notable for its high variability in X-ray
and UV wavelengths, has a low polarization consistent with a Galactic
interstellar origin.Comment: 19 pages using (AASTEX) aaspp4.sty and 5 postscript figures To be
published in the Astrophysical Journa
Combretastatin-A4 disrupts neovascular development in non-neoplastic tissue
Combretastatin-A4 phosphate (cis -CA-4) is a tubulin-binding agent currently undergoing clinical trials as an anti-tumour drug. Weâhave investigated whether CA-4 functions as a tumour-specific anti-vascular agent using the hyperplastic thyroid as a novel in vivo model of neovascularization. CA-4 elicited pathological changes in normal tissue, manifested as the induction of multiple, discrete intravascular thrombi. These vascular-damaging effects indicate that CA-4P does not function as a tumour-specific agent but targets neovasculature irrespective of the primary angiogenic stimulus. © 2001 Cancer Research Campaign http://www.bjcancer.co
Long-term optical variability of PKS 2155-304
Aims: The optical variability of the blazar PKS 2155-304 is investigated to
characterise the red noise behaviour at largely different time scales from 20
days to O(>10 yrs). Methods: The long-term optical light curve of PKS 2155-304
is assembled from archival data as well as from so-far unpublished observations
mostly carried out with the ROTSE-III and the ASAS robotic telescopes. A
forward folding technique is used to determine the best-fit parameters for a
model of a power law with a break in the power spectral density function (PSD).
The best-fit parameters are estimated using a maximum-likelihood method with
simulated light curves in conjunction with the Lomb Scargle Periodogram (LSP)
and the first-order Structure Function (SF). In addition, a new approach based
upon the so-called Multiple Fragments Variance Function (MFVF) is introduced
and compared to the other methods. Simulated light curves have been used to
confirm the reliability of these methods as well as to estimate the
uncertainties of the best-fit parameters. Results: The light curve is
consistent with the assumed broken power-law PSD. All three methods agree
within the estimated uncertainties with the MFVF providing the most accurate
results. The red-noise behaviour of the PSD in frequency f follows a power law
with f^-{\beta}, {\beta}=1.8 +0.1/-0.2 and a break towards f^0 at frequencies
lower than f_min=(2.7 +2.2/-1.6 yrs)^-1.Comment: 10 pages, 8 figures, the ROTSE-light curve can be downloaded from
http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/A+A/531/A12
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