1,575 research outputs found
Extensive HST Ultraviolet Spectra and Multi-wavelength Observations of SN 2014J in M82 Indicate Reddening and Circumstellar Scattering by Typical Dust
SN 2014J in M82 is the closest detected Type Ia supernova (SN Ia) in at least
28 years and perhaps in 410 years. Despite its small distance of 3.3 Mpc, SN
2014J is surprisingly faint, peaking at V = 10.6 mag, and assuming a typical SN
Ia luminosity, we infer an observed visual extinction of A_V = 2.0 +/- 0.1 mag.
But this picture, with R_V = 1.6 +/- 0.2, is too simple to account for all
observations. We combine 10 epochs (spanning a month) of HST/STIS ultraviolet
through near-infrared spectroscopy with HST/WFC3, KAIT, and FanCam photometry
from the optical to the infrared and 9 epochs of high-resolution TRES
spectroscopy to investigate the sources of extinction and reddening for SN
2014J. We argue that the wide range of observed properties for SN 2014J is
caused by a combination of dust reddening, likely originating in the
interstellar medium of M82, and scattering off circumstellar material. For this
model, roughly half of the extinction is caused by reddening from typical dust
(E(B-V ) = 0.45 mag and R_V = 2.6) and roughly half by scattering off LMC-like
dust in the circumstellar environment of SN 2014J.Comment: 17 pages (excluding references and tables), 15 figures, accepted to
MNRAS. A high-resolution HST image of SN 2014J in M82 is available upon
reques
Effect of P-glycoprotein modulation with cyclosporin A on cerebrospinal fluid penetration of doxorubicin in non-human primates
PURPOSE:
P-glycoprotein (Pgp) is a transmembrane drug efflux pump that is expressed in multidrug-resistant cancer cells and in a variety of normal tissues, including brain capillary endothelial cells which comprise the blood-brain barrier. We studied the effects of the Pgp inhibitor, cyclosporin A (CsA), on the cerebrospinal fluid (CSF) penetration of the Pgp substrate, doxorubicin, in non-human primates.
METHODS:
The animals received doxorubicin alone (2.0 mg/kg i.v. over 60 min) or doxorubicin (1 mg/kg i.v. over 60 min) and CsA (loading dose 4.0 mg/kg i.v. over 2 h, followed by continuous infusion of 12 mg/kg per day over 48 h). Plasma and CSF were collected over 48 h and the doxorubicin concentration was measured by reverse-phase high-pressure liquid chromatography (HPLC) with fluorescence detection (detection limit 5 nM). A two-compartment model was fitted to the plasma concentration-time data.
RESULTS:
Pgp was demonstrated to be present in the epithelium of the choroid plexus by immunohistochemical methods, indicating that CSF drug penetration could be used as a surrogate for blood-brain barrier penetration. Steady state whole blood CsA concentrations, which were measured with a fluorescence-polarization immunoassay (TDX) that detects both CsA and its metabolites, ranged from 551-1315 microg/l at 24 h. The clearance of doxorubicin in four animals was reduced by 34%, 38%, 45% and 49% when given with CsA. The doxorubicin concentration in the CSF was <5 nM in all animals, both after doxorubicin alone and doxorubicin with CsA.
CONCLUSIONS:
The Pgp inhibitor, CsA, at a concentration that alters systemic clearance of doxorubicin, does not appear to significantly increase the CSF penetration of doxorubicin
Wellness and Multiple Sclerosis: The National MS Society Establishes a Wellness Research Working Group and Research Priorities
Background:
People with multiple sclerosis (MS) have identified âwellnessâ and associated behaviors as a high priority based on âsocial media listeningâ undertaken by the National MS Society (i.e. the Society). Objective:
The Society recently convened a group that consisted of researchers with experience in MS and wellness-related research, Society staff members, and an individual with MS for developing recommendations regarding a wellness research agenda. Method:
The members of the group engaged in focal reviews and discussions involving the state of science within three approaches for promoting wellness in MS, namely diet, exercise, and emotional wellness. Results:
That process informed a group-mediated activity for developing and prioritizing research goals for wellness in MS. This served as a background for articulating the mission and objectives of the Societyâs Wellness Research Working Group. Conclusion:
The primary mission of the Wellness Research Working Group is the provision of scientific evidence supporting the application of lifestyle, behavioral, and psychosocial approaches for promoting optimal health of mind, body, and spirit (i.e. wellness) in people with MS as well as managing the disease and its consequences
AT 2017be - a new member of the class of Intermediate-Luminosity Red Transients
We report the results of our spectrophotometric monitoring campaign for
AT~2017be in NGC~2537. Its lightcurve reveals a fast rise to an optical
maximum, followed by a plateau lasting about 30 days, and finally a fast
decline. Its absolute peak magnitude ( 12 ) is
fainter than that of core-collapse supernovae, and is consistent with those of
supernova impostors and other Intermediate-Luminosity Optical Transients. The
quasi-bolometric lightcurve peaks at 2 10 erg s,
and the late-time photometry allows us to constrain an ejected Ni mass
of 8 10\msun. The spectra of AT~2017be show minor
evolution over the observational period, a relatively blue continuum showing at
early phases, which becomes redder with time. A prominent H emission
line always dominates over other Balmer lines. Weak Fe {\sc ii} features,
Ca~{\sc ii} HK and the Ca {\sc ii} NIR triplet are also visible, while
P-Cygni absorption troughs are found in a high resolution spectrum. In
addition, the [Ca~{\sc ii}] 7291,7324 doublet is visible in all
spectra. This feature is typical of Intermediate-Luminosity Red Transients
(ILRTs), similar to SN~2008S. The relatively shallow archival Spitzer data are
not particularly constraining. On the other hand, a non-detection in deeper
near-infrared HST images disfavours a massive Luminous Blue Variable eruption
as the origin for AT~2017be. As has been suggested for other ILRTs, we propose
that AT~2017be is a candidate for a weak electron-capture supernova explosion
of a super-asymptotic giant branch star, still embedded in a thick dusty
envelope.Comment: 21 pages, 15 figures, accepted by MNRA
Optical and near infrared observations of SN 2014ck: an outlier among the Type Iax supernovae
We present a comprehensive set of optical and near-infrared photometric and
spectroscopic observations for SN 2014ck, extending from pre-maximum to six
months later. These data indicate that SN 2014ck is photometrically nearly
identical to SN 2002cx, which is the prototype of the class of peculiar
transients named SNe Iax. Similar to SN 2002cx, SN 2014ck reached a peak
brightness mag, with a post-maximum decline-rate mag. However, the spectroscopic sequence shows
similarities with SN 2008ha, which was three magnitudes fainter and faster
declining. In particular, SN 2014ck exhibits extremely low ejecta velocities,
km s at maximum, which are close to the value measured for
SN 2008ha and half the value inferred for SN 2002cx. The bolometric light curve
of SN 2014ck is consistent with the production of of Ni. The spectral identification of several iron-peak
features, in particular Co II lines in the NIR, provides a clear link to SNe
Ia. Also, the detection of narrow Si, S and C features in the pre-maximum
spectra suggests a thermonuclear explosion mechanism. The late-phase spectra
show a complex overlap of both permitted and forbidden Fe, Ca and Co lines. The
appearance of strong [Ca~II] 7292, 7324 again mirrors the
late-time spectra of SN 2008ha and SN 2002cx. The photometric resemblance to SN
2002cx and the spectral similarities to SN 2008ha highlight the peculiarity of
SN 2014ck, and the complexity and heterogeneity of the SNe Iax class.Comment: MNRAS Accepted 2016 March 22. Received 2016 March
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