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Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

Objectives: To analyze the potential contribution of contractility state and ventricular geometry to the development of heart failure in rats with aortic stenosis., Methods: Rats were divided into three groups: compensated aortic stenosis (AS, n=11), heart failure AS (n=12) and control rats (C, n=13)., Results: After 21 weeks, failing AS rats presented higher systolic (C=36.6+/-3.1, AS=78.6+/-4.8*, failing AS=104.6+/-7.8*(dagger)) and diastolic meridian stress (C=6.9+/-0.4, AS=20.1+/-1.1*, failing AS=43.2+/-3.2*(dagger)), hydroxyproline (C=3.6+/-0.7 mg/g, AS=6.6+/-0.6* mg/g, failing AS=9.2+/-1.4*(dagger) mg/g) and cross-sectional area (C=338+/-25 microm2, AS=451+/-32* microm2, failing AS=508+/-36*(dagger) microm2), in comparison with control and compensated AS animals (*p<0.05 vs. control, (dagger)p<0.05 vs. AS). In the isometric contraction study, considering the time from peak tension to 50% relaxation (RT50), the relative variation responses, following post-rest contraction and increase in Ca2+ concentration, were higher in failing AS than compensated AS animals. In contrast, following post-rest contraction, compensated AS group presented higher values of the peak developed tension (DT) than failing AS group. Following beta-adrenergic stimulation, control animals presented higher values of +dT/dt and -dT/dt than AS animals. In addition, failing AS animals presented higher TPT values than compensated AS animals., Conclusion: Myocardial contractile dysfunction contributes to the development of heart failure in rats with aortic stenosis.

A new pulsating X-ray source, AX J183220-0840, with a 1549.1 s period was discovered at R.A.=18h32m20s and decl.=-8&j0;40'30" (J2000, with an uncertainty of 0&farcm;6) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1x10-11 ergs cm-2 s-1 and a pulsation period of 1549.1+/-0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat, absorbed power law with a photon index of Gamma approximately 0.8 and an absorption column density of NH approximately 1.3x1022 cm-2. Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.

We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.

Since brainstem lesion involving dorsal (DR) and median raphe (MR) nuclei have been shown to induce gastric ulcers in fasted rats, the present study was carried out to determine the mechanisms mediating this effect of the lesion, inasmuch as there is indirect evidence for a close correlation between stress-induced gastric ulcers and central serotonergic activity. Acute and simultaneous lesion of both DR and MR in 48 h fasted rats induced a significantly high incidence of gastric ulcer at the end of a 48 h period of food deprivation. Acute selective lesion of either nucleus revealed that the MR nucleus is the structure whose inactivation is related to gastric ulceration. Ulcer incidence was also high in chronically lesioned rats fasted for the same period of time. Normally fed lesioned rats and sham-operated controls did not develop ulcers, indicating that ulcers only occurred when fasting and raphe lesion were combined. We conclude that the raphe nuclei may be involved in the etiology of stress-induced gastric ulcers. The possibility of disinhibition of a general stress-related central system by the raphe lesion is discussed as the main mechanism responsible for gastric ulceration.