Rapid ischemic preconditioning (IPC) has been shown to reduce cellular injury after subsequent cardiac and cerebral ischemia. However, the data on rapid IPC of the spinal cord is limited. The authors ...investigated whether pretreatment with sublethal ischemia of spinal cord can attenuate neuronal injury after spinal cord ischemia in rabbits.
Forty-seven male New Zealand white rabbits were randomly assigned to one of three groups (n = 15 or 16 each). In the IPC(-) group, the infrarenal aorta was occluded for 17 min to produce spinal cord ischemia. In the IPC(+) group, 5 min of aortic occlusion was performed 30 min before 17 min of spinal cord ischemia. In the sham group, the aorta was not occluded. Hind limb motor function was assessed at 3 h, 24 h, 4 days, and 7 days after reperfusion using Tarlov scoring (0 = paraplegia; 4 = normal). Animals were killed for histopathologic evaluation at 24 h or 7 days after reperfusion. The number of normal neurons in the anterior spinal cord (L4-L6) was counted.
Neurologic scores were significantly higher in the IPC(+) group than the IPC(-) group at 3 and 24 h after reperfusion (P < 0.05). However, neurologic scores in the IPC(+) group gradually decreased and became similar to those in the IPC(-) group at 4 and 7 days after reperfusion. At 24 h after reperfusion, the numbers of normal neurons were significantly higher in the IPC (+) group than in the IPC(-) group (P < 0.05) and were similar between the IPC(+) and sham groups. At 7 days after reperfusion, there was no difference in the number of normal neurons between the IPC(+) and IPC(-) groups.
The results indicate that rapid IPC protects the spinal cord against neuronal damage 24 h but not 7 days after reperfusion in a rabbit model of spinal cord ischemia, suggesting that the efficacy of rapid IPC may be transient.
We study the "normal" decay phase of the X-ray afterglows of gamma-ray bursts (GRBs), which follows the shallow decay phase, using the events simultaneously observed in the R band. The classical ...external-shock model--in which neither the delayed energy injection nor time dependency of shock microphysics Is considered--shows that the decay indices of the X-ray and R-band light curves, alpha x and alpha sub(0), obey a certain relation, and that in particular, alpha sub(0) - alpha x should be larger than -1/4 unless the ambient density Increases with the distance from the central engine. For our selected 14 samples, we have found that four events violate the limit at more than the 3 a level, so that a fraction of events are outliers of the classical external-shock model at the "normal" decay phase.
We have performed a joint analysis of prompt emission from four bright short gamma-ray bursts (GRBs) with the Suzaku-WAM and the Konus-Wind experiments. This joint analysis allows us to investigate ...the spectral properties of short-duration bursts over a wider energy band with a higher accuracy. We find that these bursts have a high
$E_{\rm peak}$
, around 1MeV and have a harder power-law component than that of long GRBs. However, we can not determine whether these spectra follow the cut-off power-law model or the Band model.
We also investigated the spectral lag, hardness ratio, inferred isotropic radiation energy and existence of a soft emission hump, in order to classify them into short or long GRBs using several criteria, in addition to the burst duration. We find that all criteria, except for the existence of the soft hump, support the fact that our four GRBsamples are correctly classified as belonging to the short class. In addition, our broad-band analysis revealed that there is no evidence of GRBs with a very large hardness ratio, as seen in the BATSE short GRBsample, and that the spectral lag of our four short GRBs is consistent with zero, even in theMeV energy band, unlike long GRBs. Although our short GRBsamples are still limited, these results suggest that the spectral hardness of short GRBs might not differ significantly from that of long GRBs, and also that the spectral lag at high energies could be a strong criterion for burst classification.
ABSTRACT Isolated Swift gamma-ray burst (GRB) pulses, like their higher-energy BATSE counterparts, emit the bulk of their pulsed emission as a hard-to-soft component that can be fitted by the Norris ...et al. empirical pulse model. This signal is overlaid by a fainter, three-peaked signal that can be modeled by the residual fit of Hakkila & Preece: the two fits combine to reproduce GRB pulses with distinctive three-peaked shapes. The precursor peak appears on or before the pulse rise and is often the hardest component, the central peak is the brightest, and the decay peak converts exponentially decaying emission into a long, soft, power-law tail. Accounting for systematic instrumental differences, the general characteristics of the fitted pulses are remarkably similar. Isolated GRB pulses are dominated by hard-to-soft evolution; this is more pronounced for asymmetric pulses than for symmetric ones. Isolated GRB pulses can also exhibit intensity tracking behaviors that, when observed, are tied to the timing of the three peaks: pulses with the largest maximum hardnesses are hardest during the precursor, those with smaller maximum hardnesses are hardest during the central peak, and all pulses can re-harden during the central peak and/or during the decay peak. Since these behaviors are essentially seen in all isolated pulses, the distinction between "hard-to-soft and "intensity-tracking" pulses really no longer applies. Additionally, the triple-peaked nature of isolated GRB pulses seems to indicate that energy is injected on three separate occasions during the pulse duration: theoretical pulse models need to account for this.
We present the results of the high-redshift GRB 050904 at z
$=$
6.295 from joint spectral analysis among Swift-BAT, Konus-Wind, and Suzaku-WAM, covering a wide energy range of 15–5000 keV. The
$\nu ...F_{\nu}$
spectrum peak energy,
$E_{\rm peak}$
, was measured at 314
$^{+173}_{-89}$
keV, corresponding to 2291
$^{+1263}_{-634}$
keV in the source frame, and the isotropic equivalent radiated energy,
$E_{\rm iso}$
, was estimated to be 1.04
$^{+0.25}_{-0.17}$
$\times$
10
$^{54}$
erg. Both are among the highest values that have ever been measured. GRBs with such a high
$E_{\rm iso}$
(
$\sim$
10
$^{54}$
erg) might be associated with prompt optical emission. The derived spectral and energetic parameters are consistent with the correlation between the rest-frame
$E_{\rm p,i}$
and the
$E_{\rm iso}$
(Amati relation), but not with the correlation between the intrinsic peak energy
$E_{\rm p,i}$
and the collimation-corrected energy
$E_{\gamma}$
(Ghirlanda relation), unless the density of the circumburst environment of this burst is much larger than the nominal value, as suggested by other wavelength observations. We also discuss the possibility that this burst is an outlier in the correlation between
$E_{\rm p,i}$
and the peak luminosity
$L_{\rm p}$
(Yonetoku relation).
We investigate the possible origin of extended emissions (EEs) of short gamma-ray bursts with an isotropic energy of ~10 super(50-51) erg and a duration of a few 10s to ~100s, based on a compact ...binary (neutron star (NS)-NS or NS-black hole (BH)) merger scenario. We analyze the evolution of magnetized neutrino-dominated accretion disks of mass ~0.1 M sub(middot in circle) around BHs formed after the mergers and estimate the power of relativistic outflows via the Blandford-Znajek (BZ) process. We show that a rotation energy of the BH up to gap10 super(52) erg can be extracted with an observed timescale of gap30(1 + z) s with a relatively small disk viscosity parameter of alpha < 0.01. Such a BZ power dissipates by clashing with non-relativistic pre-ejected matter of mass M ~ 10 super(-(2-4)) M sub(middot in circle), and forms a mildly relativistic fireball. We show that the dissipative photospheric emissions from such fireballs are likely in the soft X-ray band (1-10 keV) for M ~ 10 super(-2) M sub(middot in circle), possibly in NS-NS mergers, and in the BAT band (15-150 keV) for M ~ 10 super(-4) M sub(middot in circle) possibly in NS-BH mergers. In the former case, such soft EEs can provide a good chance of ~6 yr super(-1) (DeltaOmega sub(softEE)/4pi ) (R sub(GW)/40 yr super(-1)) for simultaneous detections of the gravitational waves with a ~0degrees.1 angular resolution by soft X-ray survey facilities like the Wide-Field MAXI. Here, DeltaOmega sub(softEE) is the beaming factor of the soft EEs and R sub(GW) is the NS-NS merger rate detectable by the advanced LIGO, the advanced Virgo, and KAGRA.
A wide-field X-ray survey in the soft X-ray band is crucial for future satellite missions in the astronomical observations. HiZ-GUNDAM, currently under development, is a proposed satellite designed ...to observe soft X-ray transients including gamma-ray bursts. This satellite employs wide-field X-ray monitors consisting of lobster-eye optics and focal-plane pixel sensors in the soft X-ray band of 0.4–4 keV. A pnCCD is a candidate for focal-plane Si pixel detectors, featuring a back-illuminated X-ray CCD, large pixel size (70–100 µm), and a large active image area of approximately 55 × 55 mm2 for the flight model. Here, we investigated the basic characteristics and performance of the small-size pnCCD with 128 × 256 pixels, a pixel size of 75 µm, and a detector thickness of 450 µm. High-energy cosmic rays such as protons can degrade the performance of pnCCDs by increasing dark current and charge transfer inefficiency due to ionizing and displacement damage. These factors may affect soft X-ray observations, potentially causing the degradation of lower-detectable energy thresholds and an increase in the number of hot pixels. Therefore, we conducted a radiation tolerance test at room temperature using a proton beam. After irradiating the pnCCD with 10-MeV protons equivalent to three years of nominal operation for HiZ-GUNDAM, we found that the operation temperatures of the pnCCD should be lower than -35 °C. This requirement will be incorporated into the design of the mission operation system.
Purpose
Although the delta-opioid agonist SNC80 has been shown to attenuate hind-limb motor function and gray matter injury in normothermic rats subjected to spinal cord ischemia (SCI), its effects ...on white matter injury remain undetermined. In the present study, we investigated whether SNC80 could attenuate white matter injury in normothermic and mildly hypothermic rats.
Methods
Forty rats were randomly allocated to one of following five groups: vehicle or SNC80 with 10 min of SCI at 38°C (V-38-10m or SNC-38-10m, respectively), vehicle or SNC80 with 22 min of SCI at 35°C (V-35-22m or SNC-35-22m, respectively), or sham. SNC80 or vehicle was intrathecally administered 15 min before SCI. Forty-eight hours after reperfusion, the white matter injury was evaluated by the extent of vacuolation.
Results
The percent area of vacuolation in the ventral white matter was significantly lower in the SNC-38-10m and SNC-35-22m groups compared with that in the V-38-10m and V-35-22m groups, respectively (
P
< 0.05).
Conclusion
The results indicate that intrathecal treatment with the delta-opioid agonist SNC80 can attenuate the ventral white matter injury following SCI in rats under normothermic and mildly hypothermic conditions.
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