561 research outputs found
Market and regional segmentation and risk premia in the first era of financial globalization
We study market segmentation effects using data on U.S. railroads that list their bonds in New York and London between 1873 and 1913. This sample provides a unique setting for such analysis because of the precision offered by bond yields in cost of capital estimation, the geography-specific nature of railroad assets, and ongoing substantial technological change. We document a significant
reduction in market segmentation over time. Whilst New York bond yields exceeded those in London in the 1870s, this premium disappeared by the early 1900s. However, the segmentation premium persisted in the more remote regions of the United States.Chambers acknowledges financial support from his Keynes Fellowship, the Newton Centre for Endowment Asset Management and the Cambridge Endowment for Research in Finance, Sarkissian acknowledges financial support from the Social Sciences & Humanities Research Council of Canada, and Schill acknowledges financial support from the Darden School Foundation
Radio disappearance of the magnetar XTE J1810-197 and continued X-ray timing
We report on timing, flux density, and polarimetric observations of the
transient magnetar and 5.54 s radio pulsar XTE J1810-197 using the GBT, Nancay,
and Parkes radio telescopes beginning in early 2006, until its sudden
disappearance as a radio source in late 2008. Repeated observations through
2016 have not detected radio pulsations again. The torque on the neutron star,
as inferred from its rotation frequency derivative f-dot, decreased in an
unsteady manner by a factor of 3 in the first year of radio monitoring. In
contrast, during its final year as a detectable radio source, the torque
decreased steadily by only 9%. The period-averaged flux density, after
decreasing by a factor of 20 during the first 10 months of radio monitoring,
remained steady in the next 22 months, at an average of 0.7+/-0.3 mJy at 1.4
GHz, while still showing day-to-day fluctuations by factors of a few. There is
evidence that during this last phase of radio activity the magnetar had a steep
radio spectrum, in contrast to earlier behavior. There was no secular decrease
that presaged its radio demise. During this time the pulse profile continued to
display large variations, and polarimetry indicates that the magnetic geometry
remained consistent with that of earlier times. We supplement these results
with X-ray timing of the pulsar from its outburst in 2003 up to 2014. For the
first 4 years, XTE J1810-197 experienced non-monotonic excursions in f-dot by
at least a factor of 8. But since 2007, its f-dot has remained relatively
stable near its minimum observed value. The only apparent event in the X-ray
record that is possibly contemporaneous with the radio shut-down is a decrease
of ~20% in the hot-spot flux in 2008-2009, to a stable, minimum value. However,
the permanence of the high-amplitude, thermal X-ray pulse, even after the radio
demise, implies continuing magnetar activity.Comment: ApJ, accepted, 12 pages, 9 figure
Peculiar Spin Frequency and Radio Profile Evolution of PSR J11196127 Following Magnetar-like X-ray Bursts
We present the spin frequency and profile evolution of the radio pulsar
J11196127 following magnetar-like X-ray bursts from the system in 2016 July.
Using data from the Parkes radio telescope, we observe a smooth and fast
spin-down process subsequent to the X-ray bursts resulting in a net change in
the pulsar rotational frequency of \,Hz.
During the transition, a net spin-down rate increase of
\,Hz\,s is observed, followed by a
return of to its original value. In addition, the radio pulsations
disappeared after the X-ray bursts and reappeared about two weeks later with
the flux density at 1.4\,GHz increased by a factor of five. The flux density
then decreased and undershot the normal flux density followed by a slow
recovery back to normal. The pulsar's integrated profile underwent dramatic and
short-term changes in total intensity, polarization and position angle. Despite
the complex evolution, we observe correlations between the spin-down rate,
pulse profile shape and radio flux density. Strong single pulses have been
detected after the X-ray bursts with their energy distributions evolving with
time. The peculiar but smooth spin frequency evolution of PSR~J11196127
accompanied by systematic pulse profile and flux density changes are most
likely to be a result of either reconfiguration of the surface magnetic fields
or particle winds triggered by the X-ray bursts. The recovery of spin-down rate
and pulse profile to normal provides us the best case to study the connection
between high magnetic-field pulsars and magnetars.Comment: Accepted for publication in MNRAS on 2018 July 2
Spin-down evolution and radio disappearance of the magnetar PSR J16224950
We report on 2.4 yr of radio timing measurements of the magnetar PSR
J16224950 using the Parkes telescope, between 2011 November and 2014 March.
During this period the torque on the neutron star (inferred from the rotational
frequency derivative) varied greatly, though much less erratically than in the
2 yr following its discovery in 2009. During the last year of our measurements
the frequency derivative decreased in magnitude monotonically by 20\%, to a
value of s, a factor of 8 smaller than when
discovered. The flux density continued to vary greatly during our monitoring
through 2014 March, reaching a relatively steady low level after late 2012. The
pulse profile varied secularly on a similar timescale as the flux density and
torque. A relatively rapid transition in all three properties is evident in
early 2013. After PSR J16224950 was detected in all of our 87 observations
up to 2014 March, we did not detect the magnetar in our resumed monitoring
starting in 2015 January and have not detected it in any of the 30 observations
done through 2016 September.Comment: 8 pages, 5 figures, submitted to Ap
Five New Millisecond Pulsars From a Radio Survey of 14 Unidentified Fermi-LAT Gamma-ray Sources
We have discovered five millisecond pulsars (MSPs) in a survey of 14
unidentified Fermi-LAT sources in the southern sky using the Parkes radio
telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries,
while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived
from timing observations of PSR J0101-6422 (P =2.57 ms, DM=12 pc cm-3), we have
detected {\gamma}-ray pulsations and measured its proper motion. Its
{\gamma}-ray spectrum (a power law of {\Gamma} = 0.9 with a cutoff at 1.6 GeV)
and efficiency are typical of other MSPs, but its radio and {\gamma}-ray light
curves challenge simple geometric models of emission. The high success rate of
this survey-enabled by selecting {\gamma}-ray sources based on their detailed
spectral characteristics-and other similarly successful searches indicate that
a substantial fraction of the local population of MSPs may soon be known.Comment: 6 pages, 3 figures, 2 tables, accepted by ApJ
A Shapiro delay detection in the binary system hosting the millisecond pulsar PSR J1910-5959A
PSR J1910-5959A is a binary pulsar with a helium white dwarf companion
located about 6 arcmin from the center of the globular cluster NGC6752. Based
on 12 years of observations at the Parkes radio telescope, the relativistic
Shapiro delay has been detected in this system. We obtain a companion mass Mc =
0.180+/-0.018Msun (1sigma) implying that the pulsar mass lies in the range
1.1Msun <= Mp <= 1.5Msun. We compare our results with previous optical
determinations of the companion mass, and examine prospects for using this new
measurement for calibrating the mass-radius relation for helium white dwarfs
and for investigating their evolution in a pulsar binary system. Finally we
examine the set of binary systems hosting a millisecond pulsar and a low mass
helium white dwarf for which the mass of both stars has been measured. We
confirm that the correlation between the companion mass and the orbital period
predicted by Tauris & Savonije reproduces the observed values but find that the
predicted Mp - Pb correlation over-estimates the neutron star mass by about
0.5Msun in the orbital period range covered by the observations. Moreover, a
few systems do not obey the observed Mp - Pb correlation. We discuss these
results in the framework of the mechanisms that inhibit the accretion of matter
by a neutron star during its evolution in a low-mass X-ray binary.Comment: 4 figures, 2 tables, accepted for publication in the Astrophysical
Journa
Timing of Millisecond Pulsars in NGC 6752: Evidence for a High Mass-to-Light Ratio in the Cluster Core
Using pulse timing observations we have obtained precise parameters,
including positions with about 20 mas accuracy, of five millisecond pulsars in
NGC 6752. Three of them, located relatively close to the cluster center, have
line-of-sight accelerations larger than the maximum value predicted by the
central mass density derived from optical observation, providing dynamical
evidence for a central mass-to-light ratio >~ 10, much higher than for any
other globular cluster. It is likely that the other two millisecond pulsars
have been ejected out of the core to their present locations at 1.4 and 3.3
half-mass radii, respectively, suggesting unusual non-thermal dynamics in the
cluster core.Comment: Accepted by ApJ Letter. 5 pages, 2 figures, 1 tabl
Out of the frying pan: a young pulsar with a long radio trail emerging from SNR G315.9-0.0
The faint radio supernova remnant SNR G315.9-0.0 is notable for a long and
thin trail that extends outward perpendicular from the edge of its
approximately circular shell. In a search with the Parkes telescope we have
found a young and energetic pulsar that is located at the tip of this
collimated linear structure. PSR J1437-5959 has period P = 61 ms,
characteristic age tau_c = 114 kyr, and spin-down luminosity dE/dt = 1.4e36
erg/s. It is very faint, with a flux density at 1.4 GHz of about 75 uJy. From
its dispersion measure of 549 pc/cc, we infer d ~ 8 kpc. At this distance and
for an age comparable to tau_c, the implied pulsar velocity in the plane of the
sky is V_t = 300 km/s for a birth at the center of the SNR, although it is
possible that the SNR/pulsar system is younger than tau_c and that V_t > 300
km/s. The highly collimated linear feature is evidently the pulsar wind trail
left from the supersonic passage of PSR J1437-5959 through the interstellar
medium surrounding SNR G315.9-0.0.Comment: accepted for publication in ApJ Letter
Identification of Pro-MMP-7 as a Serum Marker for Renal Cell Carcinoma by Use of Proteomic Analysis
International audienceBACKGROUND: No validated renal cell carcinoma (RCC) marker is known for detection of asymptomatic disease in selected populations or for prognostic purposes or treatment monitoring. We identified immunogenic proteins as tumor markers for RCC by combining conventional proteome analysis with serological screening, and we investigated the diagnostic clinical value of such markers in serum. METHODS: We studied the immunogenic protein expression profile of CAL 54, a human RCC cell line, by 2-dimensional electrophoresis combined with immunoblotting using sera from healthy donors compared with RCC patients. We developed a homogeneous, fluorescent, dual-monoclonal immunoassay for metalloproteinase 7 (MMP-7) and used it to measure MMP-7 in sera from 30 healthy donors, 30 RCC patients, and 40 control patients. RESULTS: Pro-MMP-7 (29 kDa; pI 7.7) in the CAL 54 cell line secretome was an immunogenic protein reactive with RCC patient sera but not with control sera. The concentrations of pro-MMP-7 were increased (P <0.0001) in sera of RCC patients (median 7.56 microg/L; range 3.12-30.5 microg/L) compared with healthy controls (median 2.13 microg/L; range 0.17-3.5 microg/L). Serum pro-MMP-7 had a sensitivity of 93% (95% CI 78%-99%) at a specificity of 75% (59%-87%) for RCC in the samples tested. CONCLUSION: Proteomics technology combined with serology led to the identification of serum pro-MMP-7 as a marker of RCC and represents a powerful tool in searching for candidate proteins as biomarkers
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