61 research outputs found
Implications of Variability Patterns observed in TeV Blazars on the Structure of the Inner Jet
The recent long look X-ray observations of TeV blazars have revealed many
important new features concerning their time variability. In this paper, we
suggest a physical interpretation for those features based on the framework of
the internal and external shock scenarios. We present a simplified model
applicable to TeV blazars, and investigate through simulations how each of the
model parameters would affect to the observed light curve or spectrum. In
particular, we show that the internal shock scenario naturally leads to all the
observed variability properties including the structure function, but for it to
be applicable, the fractional fluctuation of the initial bulk Lorentz factors
must be small, with sigma_gamma / gamma_average < 0.01. This implies very low
dynamical efficiency of the internal shock scenario. We also suggest that
several observational quantities -- such as the characteristic time scale, the
relative amplitude of flares as compared to the steady (``offset'') component,
and the slope of the structure function -- can be used to probe the inner jet.
The results are applied to the TeV blazar Mrk421, and this, within the context
of the model, leads to the determination of several physical parameters: the
ejection of a shell with average thickness of ~1E13 cm occurs on average every
10 minutes, and the shells collide ~1E17 cm away from the central source.Comment: 12 pages, 13 figures, to appear in Ap
Urinary Titin Is Increased in Patients After Cardiac Surgery
Background: Few non-invasive biomarkers have been used to detect myocardial injury in patients with heart diseases. Recently, the N-terminal fragment (N-titin) of titin, a giant sarcomeric protein, which is involved in muscular passive tension and viscoelasticity, has been reported to detect muscle damage in patients with cardiomyopathy as well as in patients with skeletal muscle dystrophy and in healthy volunteers with endurance exercise. In the present study, we evaluated whether urinary N-titin is changed during a perioperative period and whether its increase reflects myocardial damage.Materials and Methods: In 18 patients who underwent cardiac surgery, blood and urine samples were obtained before and after surgery. We measured the urinary levels of N-titin with a highly sensitive ELISA system.Results: Urinary N-titin to creatinine (N-titin/Cr) was significantly increased in all patients postoperatively (43.3 ± 39.5 pmol/mg/dL on the day of operation) and remained significantly high for at least 4 days postoperatively. Urinary N-titin/Cr was positively correlated with serum cardiac troponin T (r = 0.36, p = 0.0006, n = 90) but not creatine kinase-MB (CK-MB). We also found that urinary N-titin/Cr in patients after a coronary artery bypass grafting operation was higher by day 2 postoperatively than in patients following open cardiac surgeries.Conclusion: The cleaved N-titin was significantly increased in urine after cardiac surgery. Urinary N-titin may be useful for detecting the risk of latent postoperative cardiac damage
Evolution of the Synchrotron Spectrum in Mrk421 during the 1998 Campaign
The uninterrupted 7-day ASCA observations of the TeV blazar Mrk421 in 1998
have clearly revealed that X-ray flares occur repeatedly. In this paper, we
present the results of the time-resolved spectral analysis of the combined data
taken by ASCA, RXTE, BeppoSAX, and EUVE. In this object - and in many other TeV
blazars - the precise measurement of the shape of the X-ray spectrum, which
reflects the high energy portion of the synchrotron component, is crucial in
determining the high energy cutoff of the accelerated electrons in the jet.
Thanks to the simultaneous broadband coverage, we measured the 0.1-25 keV
spectrum resolved on time scales as short as several hours, providing a great
opportunity to investigate the detailed spectral evolution at the flares. By
analyzing the time subdivided observations, we parameterize the evolution of
the synchrotron peak, where the radiation power dominates, by fitting the
combined spectra with a quadratic form (where the vFv flux at the energy E
obeys log vFv(E)=log(vFv_peak) - const x (log E - log Epeak)^2). In this case,
we show that there is an overall trend that the peak energy Ep and peak flux
vFvp both increase or decrease together. The relation of the two parameters is
best described as Ep \propto vFvp^{0.7} for the 1998 campaign. Similar results
were derived for the 1997 observation, while the relation gave a smaller index
when included both 1997 and 1998 data. On the other hand, we show that this
relation, and also the detailed spectral variations, differ from flare to flare
within the 1998 campaign. We suggest that the observed features are consistent
with the idea that flares are due to a appearance of a new spectral component.
With the availability of the simultaneous TeV data, we also show that there
exists a clear correlation between the synchrotron peak flux and the TeV flux.Comment: 12 pages, 9 figures, to appear in Ap
Variability Time Scales of TeV Blazars Observed in the ASCA Continuous Long-Look X-ray Monitoring
Three uninterrupted, long (lasting respectively 7, 10, and 10 days) ASCA
observations of the well-studied TeV-bright blazars Mrk 421, Mrk 501 and PKS
2155-304 all show continuous strong X-ray flaring. Despite the relatively faint
intensity states in 2 of the 3 sources, there was no identifiable quiescent
period in any of the observations. Structure function analysis shows that all
blazars have a characteristic time scale of ~ a day, comparable to the
recurrence time and to the time scale of the stronger flares. On the other
hand, examination of these flares in more detail reveals that each of the
strong flares is not a smooth increase and decrease, but exhibits substructures
of shorter flares having time scales of ~10 ks. We verify via simulations that
in order to explain the observed structure function, these shorter flares
("shots") are unlikely to be fully random, but in some way are correlated with
each other. The energy dependent cross-correlation analysis shows that
inter-band lags are not universal in TeV blazars. This is important since in
the past, only positive detections of lags were reported. In this work, we
determine that the sign of a lag may differ from flare to flare; significant
lags of both signs were detected from several flares, while no significant lag
was detected from others. However, we also argue that the nature of the
underlying component can affect these values. The facts that all flares are
nearly symmetric and that fast variability shorter than the characteristic time
scale is strongly suppressed, support the scenario where the light crossing
time dominates the variability time scales of the day-scale flares.Comment: 29 pages, 12 figures, accepted for publication in Ap
Rapid Synchrotron Flares from BL Lacertae Detected by ASCA and RXTE
We report the variable X-ray emission from BL Lacertae detected in the ASCA
ToO observation conducted during the EGRET and RXTE pointings, coincident with
the 1997 July outburst. The source showed a historically high state of X-ray,
optical, and gamma-ray emission, with its 2-10 keV flux peaking at ~3.3 E-11
erg/cm2/s. This is more than 3 times higher than the value measured by ASCA in
1995. We detected two rapid flares which occured only in the soft X-ray band,
while the hard X-ray flux also increased, but decayed with a much longer time
scale. Together with the requirement of a very steep and varying power law
dominating the soft X-ray band in addition to the hard power law, we suggest
that both the high energy end of the synchrotron spectrum and the hard inverse
Compton spectrum were visible in this source during the outburst. We discuss
the possible origins of the observed variability time scales, and interpret the
short time scales of the soft X-ray variability as reflecting the size of the
emission region.Comment: 20 pages, 4 figures, accepted for publication in the Astrophysical
Journa
Exons 45â55 Skipping Using Mutation-Tailored Cocktails of Antisense Morpholinos in the DMD Gene
Charge-changing cross section measurements of 300 MeV/nucleon Si on carbon and data analysis
Charge-changing cross section () measurements via the
transmission method have made important progress recently aiming to determine
the charge radii of exotic nuclei. In this work, we report a new
measurement of 304(9) MeV/nucleon Si on carbon at
the second Radioactive Ion Beam Line in Lanzhou (RIBLL2) and describe the data
analysis procedure in detail. This procedure is essential to evaluate the
systematic uncertainty in the transmission method. The determined
of 1125(11) mb is found to be consistent with the
existing data at similar energies. The present work will serve as a reference
in the determinations at RIBLL2.Comment: 9 pages, 13 figures, to be published in Chinese Physics
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