224 research outputs found
Magnetar-like Emission from the Young Pulsar in Kes 75
We report detection of magnetar-like X-ray bursts from the young pulsar PSR
J1846-0258, at the center of the supernova remnant Kes 75. This pulsar, long
thought to be rotation-powered, has an inferred surface dipolar magnetic field
of 4.9x10^13 G, higher than those of the vast majority of rotation-powered
pulsars, but lower than those of the ~12 previously identified magnetars. The
bursts were accompanied by a sudden flux increase and an unprecedented change
in timing behavior. These phenomena lower the magnetic and rotational
thresholds associated with magnetar-like behavior, and suggest that in neutron
stars there exists a continuum of magnetic activity that increases with
inferred magnetic field strength.Comment: 17 pages, 2 figures, accepted for publication in Science. Note: The
content of this paper is embargoed until February 21, 200
Engineering Solutions for Mitigation of Chimeric Antigen Receptor T-Cell Dysfunction
The clinical successes of chimeric antigen receptor (CAR)-T-cell therapy targeting cell surface antigens in B cell leukaemias and lymphomas has demonstrated the proof of concept that appropriately engineered T-cells have the capacity to destroy advanced cancer with long term remissions ensuing. Nevertheless, it has been significantly more problematic to effect long term clinical benefit in a solid tumour context. A major contributing factor to the clinical failure of CAR-T-cells in solid tumours has been named, almost interchangeably, as T-cell "dysfunction" or "exhaustion". While unhelpful ambiguity surrounds the term "dysfunction", "exhaustion" is canonically regarded as a pejorative term for T-cells. Recent understanding of T-cell developmental biology now identifies exhausted cells as vital for effective immune responses in the context of ongoing antigenic challenge. The purpose of this review is to explore the critical stages in the CAR-T-cell life-cycle and their various contributions to T-cell exhaustion. Through an appreciation of the predominant mechanisms of CAR-T-cell exhaustion and resultant dysfunction, we describe a range of engineering approaches to improve CAR-T-cell function
Timing behavior of the Magnetically Active Rotation-Powered Pulsar in the Supernova Remnant Kestevan 75
We report a large spin-up glitch in PSR J1846-0258 which coincided with the
onset of magnetar-like behavior on 2006 May 31. We show that the pulsar
experienced an unusually large glitch recovery, with a recovery fraction of
Q=8.7+/- 2.5, resulting in a net decrease of the pulse frequency. Such a glitch
recovery has never before been observed in a rotation-powered pulsar, however,
similar but smaller glitch over-recovery has been recently reported in the
magnetar AXP 4U~0142+61 and may have occurred in the SGR 1900+14. We also
report a large increase in the timing noise of the source. We discuss the
implications of the unusual timing behavior in PSR J1846-0258 on its status as
the first identified magnetically active rotation-powered pulsar.Comment: 14 pages, 5 figures, Accepted for publication in the Astrophysical
Journal. Incorporates changes from an anonymous referee; additional analysis
and discussion include
Exceptional flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408
(Abridged) We studied an exceptional period of activity of the anomalous
X-ray pulsar 1E 1547.0-5408 in January 2009, during which about 200 bursts were
detected by INTEGRAL. The major activity episode happened when the source was
outside the field of view of all the INTEGRAL instruments. But we were still
able to study the properties of 84 bursts detected simultaneously by the
anti-coincidence shield of the spectrometer SPI and by the detector of the
imager ISGRI. We find that the luminosity of the 22 January 2009 bursts of 1E
1547.0-5408 was > 1e42 erg/s. This luminosity is comparable to that of the
bursts of soft gamma repeaters (SGR) and is at least two orders of magnitude
larger than the luminosity of the previously reported bursts from AXPs.
Similarly to the SGR bursts, the brightest bursts of 1E 1547.0-5408 consist of
a short spike of ~100 ms duration with a hard spectrum, followed by a softer
extended tail of 1-10 s duration, which occasionally exhibits pulsations with
the source spin period of ~2 s. The observation of AXP bursts with luminosities
comparable to the one of SGR bursts strengthens the conjecture that AXPs and
SGRs are different representatives of one and the same source type.Comment: 9 pages, 10 figures, accepted to Astronomy & Astrophysic
Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts
We present results from observations of the magnetar 1E 1547.0-5408 (SGR
J1550-5418) taken with the Chandra X-ray Observatory and the Rossi X-ray Timing
Explorer (RXTE) following the source's outbursts in 2008 October and 2009
January. During the time span of the Chandra observations, which covers days 4
through 23 and days 2 through 16 after the 2008 and 2009 events, respectively,
the source spectral shape remained stable, while the pulsar's spin-down rate in
the same span in 2008 increased by a factor of 2.2 as measured by RXTE. The
lack of spectral variation suggests decoupling between magnetar spin-down and
radiative changes, hence between the spin-down-inferred magnetic field strength
and that inferred spectrally. We also found a strong anti-correlation between
the phase-averaged flux and the pulsed fraction in the 2008 and 2009 Chandra
data, but not in the pre-2008 measurements. We discuss these results in the
context of the magnetar model.Comment: 4 figures, accepted for publication in Ap
Timing Behavior of the Magnetically Active Rotation-Powered Pulsar in the Supernova Remnant Kesteven 75
We report a large spin-up glitch in PSR J1846-0258 which coincided with the onset of magnetar-like behavior on 2006 May 31. We show that the pulsar experienced an unusually large glitch recovery, with a recovery fraction of Q = 5.9+/-0.3, resulting in a net decrease of the pulse frequency. Such a glitch recovery has never before been observed in a rotation-powered pulsar, however, similar but smaller glitch over-recovery has been recently reported in the magnetar AXP 4U 0142+61 and may have occurred in the SGR 1900+14. We discuss the implications of the unusual timing behavior in PSR J1846-0258 on its status as the first identified magnetically active rotation-powered pulsar
The Long-term Radiative Evolution of Anomalous X-ray Pulsar 1E 2259+586 after its 2002 Outburst
We present an analysis of five X-ray Multi-Mirror Mission (XMM) observations
of the anomalous X-ray pulsar (AXP) 1E 2259+586 taken in 2004 and 2005 during
its relaxation following its 2002 outburst. We compare these data with those of
five previous XMM observations taken in 2002 and 2003, and find the observed
flux decay is well described by a power-law of index -0.69+/-0.03. As of
mid-2005, the source may still have been brighter than preoutburst, and was
certainly hotter. We find a strong correlation between hardness and flux, as
seen in other AXP outbursts. We discuss the implications of these results for
the magnetar model.Comment: 23 Pages, 4 figures, 3 tables, published on Ap
High-speed, multi-colour optical photometry of the anomalous X-ray pulsar 4U 0142+61 with ULTRACAM
We present high-speed, multi-colour optical photometry of the anomalous X-ray
pulsar 4U 0142+61, obtained with ULTRACAM on the 4.2-m William Herschel
Telescope. We detect 4U 0142+61 at magnitudes of i'=23.7+-0.1, g'=27.2+-0.2 and
u'>25.8, consistent with the magnitudes found by Hulleman et al.(2004) and
hence confirming their discovery of both a spectral break in the optical and a
lack of long-term optical variability. We also confirm the discovery of Kern &
Martin (2002) that 4U 0142+61 shows optical pulsations with an identical period
(~8.7 s) to the X-ray pulsations. The rms pulsed fraction in our data is
29+-8%, 5-7 times greater than the 0.2-8 keV X-ray rms pulsed fraction. The
optical and X-ray pulse profiles show similar morphologies and appear to be
approximately in phase with each other, the former lagging the latter by only
0.04+-0.02 cycles. In conjunction with the constraints imposed by X-ray
observations, the results presented here favour a magnetar interpretation for
the anomalous X-ray pulsars.Comment: 6 pages, 4 figures, accepted for publication in MNRA
Analysis Of Economic Motives In The Individual Choice Of Educational Paths
The article explores economic motive forces that drive individuals to make their choices of educational paths. This research issue is relevant in equal measure to theory — the study of economic human behavior, and practice — the enhancement of human capital investment efficiency.The authors have developed an econometric model of individual choice decisions concerning educational paths. It was implemented with the software support and bolstered with the live data on over 5.5 thousand students. To analyze the values of rational economic expectancies in the choice of educational paths, the students’ preferences were compared to the optimal, economically feasible educational paths.The findings have shown that a choice of educational paths is chiefly made in line with the economic incentives. With respect to the analyzed sample, 66% of university applicants made their choices with regard to economic preferences. Higher expected earnings after graduation — 22% of the choices, and reduction in college tuition costs or education against the budget — 12%, are the most significant factors shaping optimal educational paths.We believe that one outcome from the research is the prospect of a national policy issue for human capital investment with due regard for students and university entrants’ expectancies
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